epan/dissectors/packet-nmea0183.c

   1 /* packet-nmea0183.c
   2  * Routines for NMEA 0183 protocol dissection
   3  * Copyright 2024 Casper Meijn <casper@meijn.net>
   4  *
   5  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-or-later
  10  */
  11
  12 #include "config.h"
  13 #include <epan/packet.h>
  14 #include <epan/expert.h>
  15
  16 static int hf_nmea0183_talker_id;
  17 static int hf_nmea0183_sentence_id;
  18 static int hf_nmea0183_unknown_field;
  19 static int hf_nmea0183_checksum;
  20 static int hf_nmea0183_checksum_calculated;
  21
  22 static int hf_nmea0183_dpt_depth;
  23 static int hf_nmea0183_dpt_offset;
  24 static int hf_nmea0183_dpt_max_range;
  25
  26 static int hf_nmea0183_hdt_heading;
  27 static int hf_nmea0183_hdt_unit;
  28
  29 static int hf_nmea0183_gga_time;
  30 static int hf_nmea0183_gga_time_hour;
  31 static int hf_nmea0183_gga_time_minute;
  32 static int hf_nmea0183_gga_time_second;
  33 static int hf_nmea0183_gga_latitude;
  34 static int hf_nmea0183_gga_latitude_degree;
  35 static int hf_nmea0183_gga_latitude_minute;
  36 static int hf_nmea0183_gga_latitude_direction;
  37 static int hf_nmea0183_gga_longitude;
  38 static int hf_nmea0183_gga_longitude_degree;
  39 static int hf_nmea0183_gga_longitude_minute;
  40 static int hf_nmea0183_gga_longitude_direction;
  41 static int hf_nmea0183_gga_quality;
  42 static int hf_nmea0183_gga_number_satellites;
  43 static int hf_nmea0183_gga_horizontal_dilution;
  44 static int hf_nmea0183_gga_altitude;
  45 static int hf_nmea0183_gga_altitude_unit;
  46 static int hf_nmea0183_gga_geoidal_separation;
  47 static int hf_nmea0183_gga_geoidal_separation_unit;
  48 static int hf_nmea0183_gga_age_dgps;
  49 static int hf_nmea0183_gga_dgps_station;
  50
  51 static int hf_nmea0183_gll_latitude;
  52 static int hf_nmea0183_gll_latitude_degree;
  53 static int hf_nmea0183_gll_latitude_minute;
  54 static int hf_nmea0183_gll_latitude_direction;
  55 static int hf_nmea0183_gll_longitude;
  56 static int hf_nmea0183_gll_longitude_degree;
  57 static int hf_nmea0183_gll_longitude_minute;
  58 static int hf_nmea0183_gll_longitude_direction;
  59 static int hf_nmea0183_gll_time;
  60 static int hf_nmea0183_gll_time_hour;
  61 static int hf_nmea0183_gll_time_minute;
  62 static int hf_nmea0183_gll_time_second;
  63 static int hf_nmea0183_gll_status;
  64 static int hf_nmea0183_gll_mode;
  65
  66 static int hf_nmea0183_gst_time;
  67 static int hf_nmea0183_gst_time_hour;
  68 static int hf_nmea0183_gst_time_minute;
  69 static int hf_nmea0183_gst_time_second;
  70 static int hf_nmea0183_gst_rms_total_sd;
  71 static int hf_nmea0183_gst_ellipse_major_sd;
  72 static int hf_nmea0183_gst_ellipse_minor_sd;
  73 static int hf_nmea0183_gst_ellipse_orientation;
  74 static int hf_nmea0183_gst_latitude_sd;
  75 static int hf_nmea0183_gst_longitude_sd;
  76 static int hf_nmea0183_gst_altitude_sd;
  77
  78 static int hf_nmea0183_rot_rate_of_turn;
  79 static int hf_nmea0183_rot_valid;
  80
  81 static int hf_nmea0183_vbw_water_speed_longitudinal;
  82 static int hf_nmea0183_vbw_water_speed_transverse;
  83 static int hf_nmea0183_vbw_water_speed_valid;
  84 static int hf_nmea0183_vbw_ground_speed_longitudinal;
  85 static int hf_nmea0183_vbw_ground_speed_transverse;
  86 static int hf_nmea0183_vbw_ground_speed_valid;
  87 static int hf_nmea0183_vbw_stern_water_speed;
  88 static int hf_nmea0183_vbw_stern_water_speed_valid;
  89 static int hf_nmea0183_vbw_stern_ground_speed;
  90 static int hf_nmea0183_vbw_stern_ground_speed_valid;
  91
  92 static int hf_nmea0183_vhw_true_heading;
  93 static int hf_nmea0183_vhw_true_heading_unit;
  94 static int hf_nmea0183_vhw_magnetic_heading;
  95 static int hf_nmea0183_vhw_magnetic_heading_unit;
  96 static int hf_nmea0183_vhw_water_speed_knot;
  97 static int hf_nmea0183_vhw_water_speed_knot_unit;
  98 static int hf_nmea0183_vhw_water_speed_kilometer;
  99 static int hf_nmea0183_vhw_water_speed_kilometer_unit;
 100
 101 static int hf_nmea0183_vlw_cumulative_water;
 102 static int hf_nmea0183_vlw_cumulative_water_unit;
 103 static int hf_nmea0183_vlw_trip_water;
 104 static int hf_nmea0183_vlw_trip_water_unit;
 105 static int hf_nmea0183_vlw_cumulative_ground;
 106 static int hf_nmea0183_vlw_cumulative_ground_unit;
 107 static int hf_nmea0183_vlw_trip_ground;
 108 static int hf_nmea0183_vlw_trip_ground_unit;
 109
 110 static int hf_nmea0183_vtg_true_course;
 111 static int hf_nmea0183_vtg_true_course_unit;
 112 static int hf_nmea0183_vtg_magnetic_course;
 113 static int hf_nmea0183_vtg_magnetic_course_unit;
 114 static int hf_nmea0183_vtg_ground_speed_knot;
 115 static int hf_nmea0183_vtg_ground_speed_knot_unit;
 116 static int hf_nmea0183_vtg_ground_speed_kilometer;
 117 static int hf_nmea0183_vtg_ground_speed_kilometer_unit;
 118 static int hf_nmea0183_vtg_mode;
 119
 120 static int hf_nmea0183_zda_time;
 121 static int hf_nmea0183_zda_time_hour;
 122 static int hf_nmea0183_zda_time_minute;
 123 static int hf_nmea0183_zda_time_second;
 124 static int hf_nmea0183_zda_date_day;
 125 static int hf_nmea0183_zda_date_month;
 126 static int hf_nmea0183_zda_date_year;
 127 static int hf_nmea0183_zda_local_zone_hour;
 128 static int hf_nmea0183_zda_local_zone_minute;
 129
 130 static int ett_nmea0183;
 131 static int ett_nmea0183_checksum;
 132 static int ett_nmea0183_sentence;
 133 static int ett_nmea0183_zda_time;
 134 static int ett_nmea0183_gga_time;
 135 static int ett_nmea0183_gga_latitude;
 136 static int ett_nmea0183_gga_longitude;
 137 static int ett_nmea0183_gll_time;
 138 static int ett_nmea0183_gll_latitude;
 139 static int ett_nmea0183_gll_longitude;
 140 static int ett_nmea0183_gst_time;
 141
 142 static expert_field ei_nmea0183_invalid_first_character;
 143 static expert_field ei_nmea0183_missing_checksum_character;
 144 static expert_field ei_nmea0183_invalid_end_of_line;
 145 static expert_field ei_nmea0183_checksum_incorrect;
 146 static expert_field ei_nmea0183_sentence_too_long;
 147 static expert_field ei_nmea0183_field_time_too_short;
 148 static expert_field ei_nmea0183_field_latitude_too_short;
 149 static expert_field ei_nmea0183_field_longitude_too_short;
 150 static expert_field ei_nmea0183_field_missing;
 151 static expert_field ei_nmea0183_gga_altitude_unit_incorrect;
 152 static expert_field ei_nmea0183_gga_geoidal_separation_unit_incorrect;
 153 static expert_field ei_nmea0183_hdt_unit_incorrect;
 154 static expert_field ei_nmea0183_vhw_true_heading_unit_incorrect;
 155 static expert_field ei_nmea0183_vhw_magnetic_heading_unit_incorrect;
 156 static expert_field ei_nmea0183_vhw_water_speed_knot_unit_incorrect;
 157 static expert_field ei_nmea0183_vhw_water_speed_kilometer_unit_incorrect;
 158 static expert_field ei_nmea0183_vlw_cumulative_water_unit_incorrect;
 159 static expert_field ei_nmea0183_vlw_trip_water_unit_incorrect;
 160 static expert_field ei_nmea0183_vlw_cumulative_ground_unit_incorrect;
 161 static expert_field ei_nmea0183_vlw_trip_ground_unit_incorrect;
 162 static expert_field ei_nmea0183_vtg_true_course_unit_incorrect;
 163 static expert_field ei_nmea0183_vtg_magnetic_course_unit_incorrect;
 164 static expert_field ei_nmea0183_vtg_ground_speed_knot_unit_incorrect;
 165 static expert_field ei_nmea0183_vtg_ground_speed_kilometer_unit_incorrect;
 166
 167 static int proto_nmea0183;
 168
 169 static dissector_handle_t nmea0183_handle;
 170
 171 // List of known Talker IDs (Source: NMEA Revealed by Eric S. Raymond, https://gpsd.gitlab.io/gpsd/NMEA.html, retrieved 2023-01-26)
 172 static const string_string known_talker_ids[] = {
 173     {"AB", "Independent AIS Base Station"},
 174     {"AD", "Dependent AIS Base Station"},
 175     {"AG", "Autopilot - General"},
 176     {"AI", "Mobile AIS Station"},
 177     {"AN", "AIS Aid to Navigation"},
 178     {"AP", "Autopilot - Magnetic"},
 179     {"AR", "AIS Receiving Station"},
 180     {"AT", "AIS Transmitting Station"},
 181     {"AX", "AIS Simplex Repeater"},
 182     {"BD", "BeiDou (China)"},
 183     {"BI", "Bilge System"},
 184     {"BN", "Bridge navigational watch alarm system"},
 185     {"CA", "Central Alarm"},
 186     {"CC", "Computer - Programmed Calculator (obsolete)"},
 187     {"CD", "Communications - Digital Selective Calling (DSC)"},
 188     {"CM", "Computer - Memory Data (obsolete)"},
 189     {"CR", "Data Receiver"},
 190     {"CS", "Communications - Satellite"},
 191     {"CT", "Communications - Radio-Telephone (MF/HF)"},
 192     {"CV", "Communications - Radio-Telephone (VHF)"},
 193     {"CX", "Communications - Scanning Receiver"},
 194     {"DE", "DECCA Navigation (obsolete)"},
 195     {"DF", "Direction Finder"},
 196     {"DM", "Velocity Sensor, Speed Log, Water, Magnetic"},
 197     {"DP", "Dynamiv Position"},
 198     {"DU", "Duplex repeater station"},
 199     {"EC", "Electronic Chart Display & Information System (ECDIS)"},
 200     {"EP", "Emergency Position Indicating Beacon (EPIRB)"},
 201     {"ER", "Engine Room Monitoring Systems"},
 202     {"FD", "Fire Door"},
 203     {"FS", "Fire Sprinkler"},
 204     {"GA", "Galileo Positioning System"},
 205     {"GB", "BeiDou (China)"},
 206     {"GI", "NavIC, IRNSS (India)"},
 207     {"GL", "GLONASS, according to IEIC 61162-1"},
 208     {"GN", "Combination of multiple satellite systems (NMEA 1083)"},
 209     {"GP", "Global Positioning System receiver"},
 210     {"GQ", "QZSS regional GPS augmentation system (Japan)"},
 211     {"HC", "Heading - Magnetic Compass"},
 212     {"HD", "Hull Door"},
 213     {"HE", "Heading - North Seeking Gyro"},
 214     {"HF", "Heading - Fluxgate"},
 215     {"HN", "Heading - Non North Seeking Gyro"},
 216     {"HS", "Hull Stress"},
 217     {"II", "Integrated Instrumentation"},
 218     {"IN", "Integrated Navigation"},
 219     {"JA", "Alarm and Monitoring"},
 220     {"JB", "Water Monitoring"},
 221     {"JC", "Power Management"},
 222     {"JD", "Propulsion Control"},
 223     {"JE", "Engine Control"},
 224     {"JF", "Propulsion Boiler"},
 225     {"JG", "Aux Boiler"},
 226     {"JH", "Engine Governor"},
 227     {"LA", "Loran A (obsolete)"},
 228     {"LC", "Loran C (obsolete)"},
 229     {"MP", "Microwave Positioning System (obsolete)"},
 230     {"MX", "Multiplexer"},
 231     {"NL", "Navigation light controller"},
 232     {"OM", "OMEGA Navigation System (obsolete)"},
 233     {"OS", "Distress Alarm System (obsolete)"},
 234     {"P ", "Vendor specific"},
 235     {"QZ", "QZSS regional GPS augmentation system (Japan)"},
 236     {"RA", "RADAR and/or ARPA"},
 237     {"RB", "Record Book"},
 238     {"RC", "Propulsion Machinery"},
 239     {"RI", "Rudder Angle Indicator"},
 240     {"SA", "Physical Shore AUS Station"},
 241     {"SD", "Depth Sounder"},
 242     {"SG", "Steering Gear"},
 243     {"SN", "Electronic Positioning System, other/general"},
 244     {"SS", "Scanning Sounder"},
 245     {"ST", "Skytraq debug output"},
 246     {"TC", "Track Control"},
 247     {"TI", "Turn Rate Indicator"},
 248     {"TR", "TRANSIT Navigation System"},
 249     {"U0", "User Configured 0"},
 250     {"U1", "User Configured 1"},
 251     {"U2", "User Configured 2"},
 252     {"U3", "User Configured 3"},
 253     {"U4", "User Configured 4"},
 254     {"U5", "User Configured 5"},
 255     {"U6", "User Configured 6"},
 256     {"U7", "User Configured 7"},
 257     {"U8", "User Configured 8"},
 258     {"U9", "User Configured 9"},
 259     {"UP", "Microprocessor controller"},
 260     {"VA", "VHF Data Exchange System (VDES), ASM"},
 261     {"VD", "Velocity Sensor, Doppler, other/general"},
 262     {"VM", "Velocity Sensor, Speed Log, Water, Magnetic"},
 263     {"VR", "Voyage Data recorder"},
 264     {"VS", "VHF Data Exchange System (VDES), Satellite"},
 265     {"VT", "VHF Data Exchange System (VDES), Terrestrial"},
 266     {"VW", "Velocity Sensor, Speed Log, Water, Mechanical"},
 267     {"WD", "Watertight Door"},
 268     {"WI", "Weather Instruments"},
 269     {"WL", "Water Level"},
 270     {"YC", "Transducer - Temperature (obsolete)"},
 271     {"YD", "Transducer - Displacement, Angular or Linear (obsolete)"},
 272     {"YF", "Transducer - Frequency (obsolete)"},
 273     {"YL", "Transducer - Level (obsolete)"},
 274     {"YP", "Transducer - Pressure (obsolete)"},
 275     {"YR", "Transducer - Flow Rate (obsolete)"},
 276     {"YT", "Transducer - Tachometer (obsolete)"},
 277     {"YV", "Transducer - Volume (obsolete)"},
 278     {"YX", "Transducer"},
 279     {"ZA", "Timekeeper - Atomic Clock"},
 280     {"ZC", "Timekeeper - Chronometer"},
 281     {"ZQ", "Timekeeper - Quartz"},
 282     {"ZV", "Timekeeper - Radio Update, WWV or WWVH"},
 283     {NULL, NULL}};
 284
 285 // List of known Sentence IDs (Source: NMEA Revealed by Eric S. Raymond, https://gpsd.gitlab.io/gpsd/NMEA.html, retrieved 2023-01-26)
 286 static const string_string known_sentence_ids[] = {
 287     {"AAM", "Waypoint Arrival Alarm"},
 288     {"ACK", "Alarm Acknowledgement"},
 289     {"ADS", "Automatic Device Status"},
 290     {"AKD", "Acknowledge Detail Alarm Condition"},
 291     {"ALA", "Set Detail Alarm Condition"},
 292     {"ALM", "GPS Almanac Data"},
 293     {"APA", "Autopilot Sentence A"},
 294     {"APB", "Autopilot Sentence B"},
 295     {"ASD", "Autopilot System Data"},
 296     {"BEC", "Bearing & Distance to Waypoint - Dead Reckoning"},
 297     {"BER", "Bearing & Distance to Waypoint, Dead Reckoning, Rhumb Line"},
 298     {"BOD", "Bearing - Waypoint to Waypoint"},
 299     {"BPI", "Bearing & Distance to Point of Interest"},
 300     {"BWC", "Bearing & Distance to Waypoint - Great Circle"},
 301     {"BWR", "Bearing and Distance to Waypoint - Rhumb Line"},
 302     {"BWW", "Bearing - Waypoint to Waypoint"},
 303     {"CEK", "Configure Encryption Key Command"},
 304     {"COP", "Configure the Operational Period, Command"},
 305     {"CUR", "Water Current Layer"},
 306     {"DBK", "Depth Below Keel"},
 307     {"DBS", "Depth Below Surface"},
 308     {"DBT", "Depth below transducer"},
 309     {"DCN", "DECCA Position"},
 310     {"DCR", "Device Capability Report"},
 311     {"DDC", "Display Dimming Control"},
 312     {"DOR", "Door Status Detection"},
 313     {"DPT", "Depth of Water"},
 314     {"DRU", "Dual Doppler Auxiliary Data"},
 315     {"DSC", "Digital Selective Calling Information"},
 316     {"DSE", "Extended DSC"},
 317     {"DSI", "DSC Transponder Initiate"},
 318     {"DSR", "DSC Transponder Response"},
 319     {"DTM", "Datum Reference"},
 320     {"ETL", "Engine Telegraph Operation Status"},
 321     {"EVE", "General Event Message"},
 322     {"FIR", "Fire Detection"},
 323     {"FSI", "Frequency Set Information"},
 324     {"GBS", "GPS Satellite Fault Detection"},
 325     {"GDA", "Dead Reckoning Positions"},
 326     {"GGA", "Global Positioning System Fix Data"},
 327     {"GLa", "Loran-C Positions"},
 328     {"GLC", "Geographic Position, Loran-C"},
 329     {"GLL", "Geographic Position - Latitude/Longitude"},
 330     {"GNS", "Fix data"},
 331     {"GOA", "OMEGA Positions"},
 332     {"GRS", "GPS Range Residuals"},
 333     {"GSA", "GPS DOP and active satellites"},
 334     {"GST", "GPS Pseudorange Noise Statistics"},
 335     {"GSV", "Satellites in view"},
 336     {"GTD", "Geographic Location in Time Differences"},
 337     {"GXA", "TRANSIT Position"},
 338     {"HCC", "Compass Heading"},
 339     {"HCD", "Heading and Deviation"},
 340     {"HDG", "Heading - Deviation & Variation"},
 341     {"HDM", "Heading - Magnetic"},
 342     {"HDT", "Heading - True"},
 343     {"HFB", "Trawl Headrope to Footrope and Bottom"},
 344     {"HSC", "Heading Steering Command"},
 345     {"HVD", "Magnetic Variation, Automatic"},
 346     {"HVM", "Magnetic Variation, Manually Set"},
 347     {"IMA", "Vessel Identification"},
 348     {"ITS", "Trawl Door Spread 2 Distance"},
 349     {"LCD", "Loran-C Signal Data"},
 350     {"MDA", "Meteorological Composite"},
 351     {"MHU", "Humidity"},
 352     {"MMB", "Barometer"},
 353     {"MSK", "Control for a Beacon Receiver"},
 354     {"MSS", "Beacon Receiver Status"},
 355     {"MTA", "Air Temperature"},
 356     {"MTW", "Mean Temperature of Water"},
 357     {"MWD", "Wind Direction & Speed"},
 358     {"MWH", "Wave Height"},
 359     {"MWS", "Wind & Sea State"},
 360     {"MWV", "Wind Speed and Angle"},
 361     {"OLN", "Omega Lane Numbers"},
 362     {"OLW", "Omega Lane Width"},
 363     {"OMP", "Omega Position"},
 364     {"OSD", "Own Ship Data"},
 365     {"OZN", "Omega Zone Number"},
 366     {"R00", "Waypoints in active route"},
 367     {"RLM", "Return Link Message"},
 368     {"RMA", "Recommended Minimum Navigation Information"},
 369     {"RMB", "Recommended Minimum Navigation Information"},
 370     {"RMC", "Recommended Minimum Navigation Information"},
 371     {"Rnn", "Routes"},
 372     {"ROT", "Rate Of Turn"},
 373     {"RPM", "Revolutions"},
 374     {"RSA", "Rudder Sensor Angle"},
 375     {"RSD", "RADAR System Data"},
 376     {"RTE", "Routes"},
 377     {"SBK", "Loran-C Blink Status"},
 378     {"SCD", "Loran-C ECDs"},
 379     {"SCY", "Loran-C Cycle Lock Status"},
 380     {"SDB", "Loran-C Signal Strength"},
 381     {"SFI", "Scanning Frequency Information"},
 382     {"SGD", "Position Accuracy Estimate"},
 383     {"SGR", "Loran-C Chain Identifier"},
 384     {"SIU", "Loran-C Stations in Use"},
 385     {"SLC", "Loran-C Status"},
 386     {"SNC", "Navigation Calculation Basis"},
 387     {"SNU", "Loran-C SNR Status"},
 388     {"SPS", "Loran-C Predicted Signal Strength"},
 389     {"SSF", "Position Correction Offset"},
 390     {"STC", "Time Constant"},
 391     {"STN", "Multiple Data ID"},
 392     {"STR", "Tracking Reference"},
 393     {"SYS", "Hybrid System Configuration"},
 394     {"TDS", "Trawl Door Spread Distance"},
 395     {"TEC", "TRANSIT Satellite Error Code & Doppler Count"},
 396     {"TEP", "TRANSIT Satellite Predicted Elevation"},
 397     {"TFI", "Trawl Filling Indicator"},
 398     {"TGA", "TRANSIT Satellite Antenna & Geoidal Heights"},
 399     {"TIF", "TRANSIT Satellite Initial Flag"},
 400     {"TLB", "Target Label"},
 401     {"TLL", "Target Latitude and Longitude"},
 402     {"TPC", "Trawl Position Cartesian Coordinates"},
 403     {"TPR", "Trawl Position Relative Vessel"},
 404     {"TPT", "Trawl Position True"},
 405     {"TRF", "TRANSIT Fix Data"},
 406     {"TRP", "TRANSIT Satellite Predicted Direction of Rise"},
 407     {"TRS", "TRANSIT Satellite Operating Status"},
 408     {"TTM", "Tracked Target Message"},
 409     {"VBW", "Dual Ground/Water Speed"},
 410     {"VCD", "Current at Selected Depth"},
 411     {"VDR", "Set and Drift"},
 412     {"VHW", "Water speed and heading"},
 413     {"VLW", "Distance Traveled through Water"},
 414     {"VPE", "Speed, Dead Reckoned Parallel to True Wind"},
 415     {"VPW", "Speed - Measured Parallel to Wind"},
 416     {"VTA", "Actual Track"},
 417     {"VTG", "Track made good and Ground speed"},
 418     {"VTI", "Intended Track"},
 419     {"VWE", "Wind Track Efficiency"},
 420     {"VWR", "Relative Wind Speed and Angle"},
 421     {"VWT", "True Wind Speed and Angle"},
 422     {"WCV", "Waypoint Closure Velocity"},
 423     {"WDC", "Distance to Waypoint - Great Circle"},
 424     {"WDR", "Distance to Waypoint - Rhumb Line"},
 425     {"WFM", "Route Following Mode"},
 426     {"WNC", "Distance - Waypoint to Waypoint"},
 427     {"WNR", "Waypoint-to-Waypoint Distance, Rhumb Line"},
 428     {"WPL", "Waypoint Location"},
 429     {"XDR", "Transducer Measurement"},
 430     {"XTE", "Cross-Track Error, Measured"},
 431     {"XTR", "Cross Track Error - Dead Reckoning"},
 432     {"YWP", "Water Propagation Speed"},
 433     {"YWS", "Water Profile"},
 434     {"ZAA", "Time, Elapsed/Estimated"},
 435     {"ZCD", "Timer"},
 436     {"ZDA", "Time & Date - UTC, day, month, year and local time zone"},
 437     {"ZDL", "Time and Distance to Variable Point"},
 438     {"ZEV", "Event Timer"},
 439     {"ZFO", "UTC & Time from origin Waypoint"},
 440     {"ZLZ", "Time of Day"},
 441     {"ZTG", "UTC & Time to Destination Waypoint"},
 442     {"ZZU", "Time, UTC"},
 443     {NULL, NULL}};
 444
 445 // List of GPS Quality Indicator (Source: NMEA Revealed by Eric S. Raymond, https://gpsd.gitlab.io/gpsd/NMEA.html, retrieved 2023-01-26)
 446 static const string_string known_gps_quality_indicators[] = {
 447     {"0", "Fix not available"},
 448     {"1", "GPS fix"},
 449     {"2", "Differential GPS fix"},
 450     {"3", "PPS fix"},
 451     {"4", "Real Time Kinematic"},
 452     {"5", "Float Real Time Kinematic"},
 453     {"6", "Estimated (dead reckoning)"},
 454     {"7", "Manual input mode"},
 455     {"8", "Simulation mode"},
 456     {NULL, NULL}};
 457
 458 // List of status indicators (Source: NMEA Revealed by Eric S. Raymond, https://gpsd.gitlab.io/gpsd/NMEA.html, retrieved 2024-04-19)
 459 static const string_string known_status_indicators[] = {
 460     {"A", "Valid/Active"},
 461     {"V", "Invalid/Void"},
 462     {NULL, NULL}};
 463
 464 // List of FAA Mode Indicator (Source: NMEA Revealed by Eric S. Raymond, https://gpsd.gitlab.io/gpsd/NMEA.html, retrieved 2024-04-19)
 465 static const string_string known_faa_mode_indicators[] = {
 466     {"A", "Autonomous mode"},
 467     {"C", "Quectel Querk, Caution"},
 468     {"D", "Differential Mode"},
 469     {"E", "Estimated (dead-reckoning) mode"},
 470     {"F", "RTK Float mode"},
 471     {"M", "Manual Input Mode"},
 472     {"N", "Data Not Valid"},
 473     {"P", "Precise"},
 474     {"R", "RTK Integer mode"},
 475     {"S", "Simulated Mode"},
 476     {"U", "Quectel Querk, Unsafe"},
 477     {NULL, NULL}};
 478
 479 static uint8_t calculate_checksum(tvbuff_t *tvb, const int start, const int length)
 480 {
 481     uint8_t checksum = 0;
 482     for (int i = start; i < start + length; i++)
 483     {
 484         checksum ^= tvb_get_uint8(tvb, i);
 485     }
 486     return checksum;
 487 }
 488
 489 /* Find first occurrence of a field separator in tvbuff, starting at offset. Searches
 490  * to end of tvbuff.
 491  * Returns the offset of the found separator.
 492  * If separator is not found, return the offset of end of tvbuff.
 493  * If offset is out of bounds, return the offset of end of tvbuff.
 494  **/
 495 static int
 496 tvb_find_end_of_nmea0183_field(tvbuff_t *tvb, const int offset)
 497 {
 498     if (tvb_captured_length_remaining(tvb, offset) == 0)
 499     {
 500         return tvb_captured_length(tvb);
 501     }
 502
 503     int end_of_field_offset = tvb_find_uint8(tvb, offset, -1, ',');
 504     if (end_of_field_offset == -1)
 505     {
 506         return tvb_captured_length(tvb);
 507     }
 508     return end_of_field_offset;
 509 }
 510
 511 /* Add a zero length item which indicates an expected but missing field */
 512 static proto_item *
 513 proto_tree_add_missing_field(proto_tree *tree, packet_info *pinfo, int hf, tvbuff_t *tvb,
 514                              const int offset)
 515 {
 516     proto_item *ti = NULL;
 517     ti = proto_tree_add_item(tree, hf, tvb, offset, 0, ENC_ASCII);
 518     proto_item_append_text(ti, "[missing]");
 519     expert_add_info(pinfo, ti, &ei_nmea0183_field_missing);
 520     return ti;
 521 }
 522
 523 /* Dissect a time field. The field is split into a tree with hour, minute and second elements.
 524  * Returns length including separator
 525  **/
 526 static int
 527 dissect_nmea0183_field_time(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset,
 528                             int hf_time, int hf_hour, int hf_minute, int hf_second, int ett_time)
 529 {
 530     if (offset > (int)tvb_captured_length(tvb))
 531     {
 532         proto_tree_add_missing_field(tree, pinfo, hf_time, tvb, tvb_captured_length(tvb));
 533         return 0;
 534     }
 535
 536     proto_item *ti = NULL;
 537     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 538     ti = proto_tree_add_item(tree, hf_time, tvb, offset, end_of_field_offset - offset, ENC_ASCII);
 539     if (end_of_field_offset - offset == 0)
 540     {
 541         proto_item_append_text(ti, ": [empty]");
 542     }
 543     else if (end_of_field_offset - offset >= 6)
 544     {
 545         const uint8_t *hour = NULL;
 546         const uint8_t *minute = NULL;
 547         const uint8_t *second = NULL;
 548         proto_tree *time_subtree = proto_item_add_subtree(ti, ett_time);
 549
 550         proto_tree_add_item_ret_string(time_subtree, hf_hour,
 551                                        tvb, offset, 2, ENC_ASCII,
 552                                        pinfo->pool, &hour);
 553
 554         proto_tree_add_item_ret_string(time_subtree, hf_minute,
 555                                        tvb, offset + 2, 2, ENC_ASCII,
 556                                        pinfo->pool, &minute);
 557
 558         proto_tree_add_item_ret_string(time_subtree, hf_second,
 559                                        tvb, offset + 4, end_of_field_offset - offset - 4,
 560                                        ENC_ASCII, pinfo->pool, &second);
 561
 562         proto_item_append_text(ti, ": %s:%s:%s", hour, minute, second);
 563     }
 564     else
 565     {
 566         expert_add_info(pinfo, ti, &ei_nmea0183_field_time_too_short);
 567     }
 568     return end_of_field_offset - offset + 1;
 569 }
 570
 571 /* Dissect a single field containing a dimensionless value. Returns length including separator */
 572 static int
 573 dissect_nmea0183_field(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, int hf, const char *suffix)
 574 {
 575     if (offset > (int)tvb_captured_length(tvb))
 576     {
 577         proto_tree_add_missing_field(tree, pinfo, hf, tvb, tvb_captured_length(tvb));
 578         return 0;
 579     }
 580
 581     proto_item *ti = NULL;
 582     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 583     ti = proto_tree_add_item(tree, hf, tvb, offset, end_of_field_offset - offset, ENC_ASCII);
 584     if (end_of_field_offset - offset == 0)
 585     {
 586         proto_item_append_text(ti, "[empty]");
 587     }
 588     else if (suffix != NULL)
 589     {
 590         proto_item_append_text(ti, " %s", suffix);
 591     }
 592     return end_of_field_offset - offset + 1;
 593 }
 594
 595 /* Dissect a latitude/longitude direction field.
 596  * Returns length including separator
 597  **/
 598 static int
 599 dissect_nmea0183_field_latlong_direction(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 600                                          int offset, int hf,
 601                                          wmem_allocator_t *scope, const uint8_t **retval)
 602 {
 603     if (offset > (int)tvb_captured_length(tvb))
 604     {
 605         proto_tree_add_missing_field(tree, pinfo, hf, tvb, tvb_captured_length(tvb));
 606         return 0;
 607     }
 608
 609     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 610     proto_item *ti = proto_tree_add_item_ret_string(tree, hf,
 611                                                     tvb, offset, end_of_field_offset - offset, ENC_ASCII,
 612                                                     scope, retval);
 613     if (end_of_field_offset - offset == 0)
 614     {
 615         if (retval == NULL)
 616         {
 617             proto_item_append_text(ti, "[empty]");
 618         }
 619         else
 620         {
 621             proto_item_append_text(ti, "[missing]");
 622             expert_add_info(pinfo, ti, &ei_nmea0183_field_missing);
 623         }
 624     }
 625     return end_of_field_offset - offset + 1;
 626 }
 627
 628 /* Dissect a latitude field + direction field. The fields are split into a tree with degree, minute and direction elements.
 629  * Returns length including separator
 630  **/
 631 static int
 632 dissect_nmea0183_field_latitude(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset,
 633                                 int hf_latitude, int hf_degree, int hf_minute, int hf_direction, int ett_latitude)
 634 {
 635     if (offset > (int)tvb_captured_length(tvb))
 636     {
 637         proto_tree_add_missing_field(tree, pinfo, hf_latitude, tvb, tvb_captured_length(tvb));
 638         return 0;
 639     }
 640
 641     proto_item *ti = NULL;
 642     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 643     ti = proto_tree_add_item(tree, hf_latitude, tvb, offset, end_of_field_offset - offset, ENC_ASCII);
 644     if (end_of_field_offset - offset == 0)
 645     {
 646         proto_item_append_text(ti, "[empty]");
 647
 648         end_of_field_offset += dissect_nmea0183_field_latlong_direction(tvb, pinfo, tree, end_of_field_offset + 1, hf_direction, NULL, NULL);
 649     }
 650     else if (end_of_field_offset - offset >= 4)
 651     {
 652         const uint8_t *degree = NULL;
 653         const uint8_t *minute = NULL;
 654         const uint8_t *direction = NULL;
 655         proto_tree *latitude_subtree = proto_item_add_subtree(ti, ett_latitude);
 656
 657         proto_tree_add_item_ret_string(latitude_subtree, hf_degree,
 658                                        tvb, offset, 2,
 659                                        ENC_ASCII, pinfo->pool, &degree);
 660
 661         proto_tree_add_item_ret_string(latitude_subtree, hf_minute,
 662                                        tvb, offset + 2, end_of_field_offset - offset - 2,
 663                                        ENC_ASCII, pinfo->pool, &minute);
 664
 665         end_of_field_offset += dissect_nmea0183_field_latlong_direction(tvb, pinfo, latitude_subtree, end_of_field_offset + 1, hf_direction, pinfo->pool, &direction);
 666
 667         proto_item_append_text(ti, ": %s° %s' %s", degree, minute, direction);
 668     }
 669     else
 670     {
 671         expert_add_info(pinfo, ti, &ei_nmea0183_field_latitude_too_short);
 672
 673         end_of_field_offset += dissect_nmea0183_field_latlong_direction(tvb, pinfo, tree, end_of_field_offset + 1, hf_direction, NULL, NULL);
 674     }
 675     return end_of_field_offset - offset + 1;
 676 }
 677
 678 /* Dissect a longitude field + direction field. The fields are split into a tree with degree, minute and direction elements.
 679  * Returns length including separator
 680  **/
 681 static int
 682 dissect_nmea0183_field_longitude(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset,
 683                                  int hf_longitude, int hf_degree, int hf_minute, int hf_direction, int ett_latitude)
 684 {
 685     if (offset > (int)tvb_captured_length(tvb))
 686     {
 687         proto_tree_add_missing_field(tree, pinfo, hf_longitude, tvb, tvb_captured_length(tvb));
 688         return 0;
 689     }
 690
 691     proto_item *ti = NULL;
 692     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 693     ti = proto_tree_add_item(tree, hf_longitude, tvb, offset, end_of_field_offset - offset, ENC_ASCII);
 694     if (end_of_field_offset - offset == 0)
 695     {
 696         proto_item_append_text(ti, "[empty]");
 697
 698         end_of_field_offset += dissect_nmea0183_field_latlong_direction(tvb, pinfo, tree, end_of_field_offset + 1, hf_direction, NULL, NULL);
 699     }
 700     else if (end_of_field_offset - offset >= 5)
 701     {
 702         const uint8_t *degree = NULL;
 703         const uint8_t *minute = NULL;
 704         const uint8_t *direction = NULL;
 705         proto_tree *longitude_subtree = proto_item_add_subtree(ti, ett_latitude);
 706
 707         proto_tree_add_item_ret_string(longitude_subtree, hf_degree,
 708                                        tvb, offset, 3,
 709                                        ENC_ASCII, pinfo->pool, &degree);
 710
 711         proto_tree_add_item_ret_string(longitude_subtree, hf_minute,
 712                                        tvb, offset + 3, end_of_field_offset - offset - 3,
 713                                        ENC_ASCII, pinfo->pool, &minute);
 714
 715         end_of_field_offset += dissect_nmea0183_field_latlong_direction(tvb, pinfo, longitude_subtree, end_of_field_offset + 1, hf_direction, pinfo->pool, &direction);
 716
 717         proto_item_append_text(ti, ": %s° %s' %s", degree, minute, direction);
 718     }
 719     else
 720     {
 721         expert_add_info(pinfo, ti, &ei_nmea0183_field_longitude_too_short);
 722
 723         end_of_field_offset += dissect_nmea0183_field_latlong_direction(tvb, pinfo, tree, end_of_field_offset + 1, hf_direction, NULL, NULL);
 724     }
 725     return end_of_field_offset - offset + 1;
 726 }
 727
 728 /* Dissect a required gps quality field. Returns length including separator */
 729 static int
 730 dissect_nmea0183_field_gps_quality(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, int hf)
 731 {
 732     if (offset > (int)tvb_captured_length(tvb))
 733     {
 734         proto_tree_add_missing_field(tree, pinfo, hf, tvb, tvb_captured_length(tvb));
 735         return 0;
 736     }
 737
 738     proto_item *ti = NULL;
 739     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 740     const uint8_t *quality = NULL;
 741     ti = proto_tree_add_item_ret_string(tree, hf,
 742                                         tvb, offset, end_of_field_offset - offset, ENC_ASCII,
 743                                         pinfo->pool, &quality);
 744     if (end_of_field_offset - offset == 0)
 745     {
 746         proto_item_append_text(ti, "[missing]");
 747         expert_add_info(pinfo, ti, &ei_nmea0183_field_missing);
 748     }
 749     else
 750     {
 751         proto_item_append_text(ti, " (%s)", str_to_str(quality, known_gps_quality_indicators, "Unknown quality"));
 752     }
 753     return end_of_field_offset - offset + 1;
 754 }
 755
 756 /* Dissect a single field containing a fixed text.
 757     The text of the field must match the `expected_text` or expert info `invalid_ei` is
 758     added to the field. An empty field is allowed. Returns length including separator */
 759 static int
 760 dissect_nmea0183_field_fixed_text(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, int hf,
 761                                   const uint8_t *expected_text, expert_field *invalid_ei)
 762 {
 763     if (offset > (int)tvb_captured_length(tvb))
 764     {
 765         proto_tree_add_missing_field(tree, pinfo, hf, tvb, tvb_captured_length(tvb));
 766         return 0;
 767     }
 768
 769     proto_item *ti = NULL;
 770     const uint8_t *text = NULL;
 771     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 772     ti = proto_tree_add_item_ret_string(tree, hf,
 773                                         tvb, offset, end_of_field_offset - offset, ENC_ASCII,
 774                                         pinfo->pool, &text);
 775     if (end_of_field_offset - offset == 0)
 776     {
 777         proto_item_append_text(ti, "[empty]");
 778     }
 779     else if (g_ascii_strcasecmp(text, expected_text) != 0)
 780     {
 781         expert_add_info(pinfo, ti, invalid_ei);
 782     }
 783     return end_of_field_offset - offset + 1;
 784 }
 785
 786 /* Dissect a optional FAA mode indicator field. Returns length including separator */
 787 static int
 788 dissect_nmea0183_field_faa_mode(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, int hf)
 789 {
 790     if (offset > (int)tvb_captured_length(tvb))
 791     {
 792         proto_tree_add_missing_field(tree, pinfo, hf, tvb, tvb_captured_length(tvb));
 793         return 0;
 794     }
 795
 796     proto_item *ti = NULL;
 797     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 798     const uint8_t *mode = NULL;
 799     ti = proto_tree_add_item_ret_string(tree, hf,
 800                                         tvb, offset, end_of_field_offset - offset, ENC_ASCII,
 801                                         pinfo->pool, &mode);
 802     if (end_of_field_offset - offset == 0)
 803     {
 804         proto_item_append_text(ti, "[empty]");
 805     }
 806     else
 807     {
 808         proto_item_append_text(ti, " (%s)", str_to_str(mode, known_faa_mode_indicators, "Unknown FAA mode"));
 809     }
 810     return end_of_field_offset - offset + 1;
 811 }
 812
 813 /* Dissect a optional A/V status field. Returns length including separator */
 814 static int
 815 dissect_nmea0183_field_status(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offset, int hf)
 816 {
 817     if (offset > (int)tvb_captured_length(tvb))
 818     {
 819         proto_tree_add_missing_field(tree, pinfo, hf, tvb, tvb_captured_length(tvb));
 820         return 0;
 821     }
 822
 823     proto_item *ti = NULL;
 824     int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
 825     const uint8_t *mode = NULL;
 826     ti = proto_tree_add_item_ret_string(tree, hf,
 827                                         tvb, offset, end_of_field_offset - offset, ENC_ASCII,
 828                                         pinfo->pool, &mode);
 829     if (end_of_field_offset - offset == 0)
 830     {
 831         proto_item_append_text(ti, "[empty]");
 832     }
 833     else
 834     {
 835         proto_item_append_text(ti, " (%s)", str_to_str(mode, known_status_indicators, "Unknown status"));
 836     }
 837     return end_of_field_offset - offset + 1;
 838 }
 839
 840 /* Dissect a DPT sentence. */
 841 static int
 842 dissect_nmea0183_sentence_dpt(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 843 {
 844     int offset = 0;
 845
 846     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
 847                                                  tvb_captured_length(tvb), ett_nmea0183_sentence, NULL, "DPT sentence - Depth of Water");
 848
 849     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_dpt_depth, "meter");
 850
 851     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_dpt_offset, "meter");
 852
 853     dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_dpt_max_range, "meter");
 854
 855     return tvb_captured_length(tvb);
 856 }
 857
 858 /* Dissect a GGA sentence. The time, latitude and longitude fields is split into individual parts. */
 859 static int
 860 dissect_nmea0183_sentence_gga(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 861 {
 862     int offset = 0;
 863
 864     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
 865                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
 866                                                  NULL, "GGA sentence - Global Positioning System Fix");
 867
 868     offset += dissect_nmea0183_field_time(tvb, pinfo, subtree, offset, hf_nmea0183_gga_time,
 869                                           hf_nmea0183_gga_time_hour, hf_nmea0183_gga_time_minute,
 870                                           hf_nmea0183_gga_time_second, ett_nmea0183_gga_time);
 871
 872     offset += dissect_nmea0183_field_latitude(tvb, pinfo, subtree, offset, hf_nmea0183_gga_latitude,
 873                                               hf_nmea0183_gga_latitude_degree, hf_nmea0183_gga_latitude_minute,
 874                                               hf_nmea0183_gga_latitude_direction, ett_nmea0183_gga_latitude);
 875
 876     offset += dissect_nmea0183_field_longitude(tvb, pinfo, subtree, offset, hf_nmea0183_gga_longitude,
 877                                                hf_nmea0183_gga_longitude_degree, hf_nmea0183_gga_longitude_minute,
 878                                                hf_nmea0183_gga_longitude_direction, ett_nmea0183_gga_longitude);
 879
 880     offset += dissect_nmea0183_field_gps_quality(tvb, pinfo, subtree, offset, hf_nmea0183_gga_quality);
 881
 882     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gga_number_satellites, NULL);
 883
 884     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gga_horizontal_dilution, "meter");
 885
 886     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gga_altitude, "meter");
 887
 888     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_gga_altitude_unit,
 889                                                 "M", &ei_nmea0183_gga_altitude_unit_incorrect);
 890
 891     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gga_geoidal_separation, "meter");
 892
 893     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_gga_geoidal_separation_unit,
 894                                                 "M", &ei_nmea0183_gga_geoidal_separation_unit_incorrect);
 895
 896     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gga_age_dgps, "second");
 897
 898     dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gga_dgps_station, NULL);
 899
 900     return tvb_captured_length(tvb);
 901 }
 902
 903 /* Dissect a GLL sentence. The latitude, longitude and time fields is split into individual parts. */
 904 static int
 905 dissect_nmea0183_sentence_gll(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 906 {
 907     int offset = 0;
 908
 909     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
 910                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
 911                                                  NULL, "GLL sentence - Geographic Position");
 912
 913     offset += dissect_nmea0183_field_latitude(tvb, pinfo, subtree, offset, hf_nmea0183_gll_latitude,
 914                                               hf_nmea0183_gll_latitude_degree, hf_nmea0183_gll_latitude_minute,
 915                                               hf_nmea0183_gll_latitude_direction, ett_nmea0183_gll_latitude);
 916
 917     offset += dissect_nmea0183_field_longitude(tvb, pinfo, subtree, offset, hf_nmea0183_gll_longitude,
 918                                                hf_nmea0183_gll_longitude_degree, hf_nmea0183_gll_longitude_minute,
 919                                                hf_nmea0183_gll_longitude_direction, ett_nmea0183_gll_longitude);
 920
 921     offset += dissect_nmea0183_field_time(tvb, pinfo, subtree, offset, hf_nmea0183_gll_time,
 922                                           hf_nmea0183_gll_time_hour, hf_nmea0183_gll_time_minute,
 923                                           hf_nmea0183_gll_time_second, ett_nmea0183_gll_time);
 924
 925     offset += dissect_nmea0183_field_status(tvb, pinfo, subtree, offset, hf_nmea0183_gll_status);
 926
 927     dissect_nmea0183_field_faa_mode(tvb, pinfo, subtree, offset, hf_nmea0183_gll_mode);
 928
 929     return tvb_captured_length(tvb);
 930 }
 931
 932 /* Dissect a GST sentence. The time field is split into individual parts. */
 933 static int
 934 dissect_nmea0183_sentence_gst(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 935 {
 936     int offset = 0;
 937
 938     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
 939                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
 940                                                  NULL, "GST sentence - GPS Pseudorange Noise Statistics");
 941
 942     offset += dissect_nmea0183_field_time(tvb, pinfo, subtree, offset, hf_nmea0183_gst_time,
 943                                           hf_nmea0183_gst_time_hour, hf_nmea0183_gst_time_minute,
 944                                           hf_nmea0183_gst_time_second, ett_nmea0183_gst_time);
 945
 946     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_rms_total_sd, "");
 947
 948     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_ellipse_major_sd, "meter");
 949     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_ellipse_minor_sd, "meter");
 950     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_ellipse_orientation, "degree (true north)");
 951
 952     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_latitude_sd, "meter");
 953     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_longitude_sd, "meter");
 954     dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_gst_altitude_sd, "meter");
 955
 956     return tvb_captured_length(tvb);
 957 }
 958
 959 /* Dissect a HDT sentence. */
 960 static int
 961 dissect_nmea0183_sentence_hdt(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 962 {
 963     int offset = 0;
 964
 965     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
 966                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
 967                                                  NULL, "HDT sentence - True Heading");
 968
 969     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_hdt_heading, "degree");
 970
 971     dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_hdt_unit,
 972                                       "T", &ei_nmea0183_hdt_unit_incorrect);
 973
 974     return tvb_captured_length(tvb);
 975 }
 976
 977 /* Dissect a ROT sentence. */
 978 static int
 979 dissect_nmea0183_sentence_rot(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 980 {
 981     int offset = 0;
 982
 983     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
 984                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
 985                                                  NULL, "ROT sentence - Rate Of Turn");
 986
 987     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_rot_rate_of_turn, "degree per minute");
 988
 989     dissect_nmea0183_field_status(tvb, pinfo, subtree, offset, hf_nmea0183_rot_valid);
 990
 991     return tvb_captured_length(tvb);
 992 }
 993
 994 /* Dissect a VHW sentence. */
 995 static int
 996 dissect_nmea0183_sentence_vhw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 997 {
 998     int offset = 0;
 999
1000     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
1001                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
1002                                                  NULL, "VHW sentence - Water speed and heading");
1003
1004     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_true_heading, "degree");
1005
1006     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_true_heading_unit,
1007                                                 "T", &ei_nmea0183_vhw_true_heading_unit_incorrect);
1008
1009     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_magnetic_heading, "degree");
1010
1011     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_magnetic_heading_unit,
1012                                                 "M", &ei_nmea0183_vhw_magnetic_heading_unit_incorrect);
1013
1014     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_water_speed_knot, "knot");
1015
1016     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_water_speed_knot_unit,
1017                                                 "N", &ei_nmea0183_vhw_water_speed_knot_unit_incorrect);
1018
1019     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_water_speed_kilometer, "kilometer per hour");
1020
1021     dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vhw_water_speed_kilometer_unit,
1022                                       "K", &ei_nmea0183_vhw_water_speed_kilometer_unit_incorrect);
1023
1024     return tvb_captured_length(tvb);
1025 }
1026
1027 /* Dissect a VBW sentence. */
1028 static int
1029 dissect_nmea0183_sentence_vbw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
1030 {
1031     int offset = 0;
1032
1033     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
1034                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
1035                                                  NULL, "VBW sentence - Dual Ground/Water Speed");
1036
1037     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_water_speed_longitudinal, "knot");
1038     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_water_speed_transverse, "knot");
1039     offset += dissect_nmea0183_field_status(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_water_speed_valid);
1040
1041     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_ground_speed_longitudinal, "knot");
1042     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_ground_speed_transverse, "knot");
1043     offset += dissect_nmea0183_field_status(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_ground_speed_valid);
1044
1045     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_stern_water_speed, "knot");
1046     offset += dissect_nmea0183_field_status(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_stern_water_speed_valid);
1047
1048     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_stern_ground_speed, "knot");
1049     dissect_nmea0183_field_status(tvb, pinfo, subtree, offset, hf_nmea0183_vbw_stern_ground_speed_valid);
1050
1051     return tvb_captured_length(tvb);
1052 }
1053
1054 /* Dissect a VLW sentence. */
1055 static int
1056 dissect_nmea0183_sentence_vlw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
1057 {
1058     int offset = 0;
1059
1060     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
1061                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
1062                                                  NULL, "VLW sentence - Distance Traveled through Water");
1063
1064     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_cumulative_water, "nautical miles");
1065
1066     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_cumulative_water_unit,
1067                                                 "N", &ei_nmea0183_vlw_cumulative_water_unit_incorrect);
1068
1069     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_trip_water, "nautical miles");
1070
1071     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_trip_water_unit,
1072                                                 "N", &ei_nmea0183_vlw_trip_water_unit_incorrect);
1073
1074     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_cumulative_ground, "nautical miles");
1075
1076     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_cumulative_ground_unit,
1077                                                 "N", &ei_nmea0183_vlw_cumulative_ground_unit_incorrect);
1078
1079     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_trip_ground, "nautical miles");
1080
1081     dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vlw_trip_ground_unit,
1082                                       "N", &ei_nmea0183_vlw_trip_ground_unit_incorrect);
1083
1084     return tvb_captured_length(tvb);
1085 }
1086
1087 /* Dissect a VTG sentence. */
1088 static int
1089 dissect_nmea0183_sentence_vtg(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
1090 {
1091     int offset = 0;
1092
1093     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
1094                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
1095                                                  NULL, "VTG sentence - Track made good and Ground speed");
1096
1097     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_true_course, "degree");
1098
1099     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_true_course_unit,
1100                                                 "T", &ei_nmea0183_vtg_true_course_unit_incorrect);
1101
1102     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_magnetic_course, "degree");
1103
1104     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_magnetic_course_unit,
1105                                                 "M", &ei_nmea0183_vtg_magnetic_course_unit_incorrect);
1106
1107     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_ground_speed_knot, "knot");
1108
1109     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_ground_speed_knot_unit,
1110                                                 "N", &ei_nmea0183_vtg_ground_speed_knot_unit_incorrect);
1111
1112     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_ground_speed_kilometer, "kilometer per hour");
1113
1114     offset += dissect_nmea0183_field_fixed_text(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_ground_speed_kilometer_unit,
1115                                                 "K", &ei_nmea0183_vtg_ground_speed_kilometer_unit_incorrect);
1116
1117     dissect_nmea0183_field_faa_mode(tvb, pinfo, subtree, offset, hf_nmea0183_vtg_mode);
1118
1119     return tvb_captured_length(tvb);
1120 }
1121
1122 /* Dissect a ZDA (Time & Date) sentence. The time field is split into individual parts. */
1123 static int
1124 dissect_nmea0183_sentence_zda(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
1125 {
1126     int offset = 0;
1127     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
1128                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
1129                                                  NULL, "ZDA sentence - Time & Date");
1130
1131     offset += dissect_nmea0183_field_time(tvb, pinfo, subtree, offset, hf_nmea0183_zda_time,
1132                                           hf_nmea0183_zda_time_hour, hf_nmea0183_zda_time_minute,
1133                                           hf_nmea0183_zda_time_second, ett_nmea0183_zda_time);
1134
1135     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_zda_date_day, NULL);
1136
1137     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_zda_date_month, NULL);
1138
1139     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_zda_date_year, NULL);
1140
1141     offset += dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_zda_local_zone_hour, NULL);
1142
1143     dissect_nmea0183_field(tvb, pinfo, subtree, offset, hf_nmea0183_zda_local_zone_minute, NULL);
1144
1145     return tvb_captured_length(tvb);
1146 }
1147
1148 /* Dissect a sentence where the sentence id is unknown. Each field is shown as an generic field. */
1149 static int
1150 dissect_nmea0183_sentence_unknown(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree)
1151 {
1152     int offset = 0;
1153
1154     proto_tree *subtree = proto_tree_add_subtree(tree, tvb, offset,
1155                                                  tvb_captured_length(tvb), ett_nmea0183_sentence,
1156                                                  NULL, "Unknown sentence");
1157
1158     /* In an unknown sentence, the name of each field is unknown. Find all field by splitting at a comma. */
1159     while (tvb_captured_length_remaining(tvb, offset) > 0)
1160     {
1161         int end_of_field_offset = tvb_find_end_of_nmea0183_field(tvb, offset);
1162         proto_item *ti = proto_tree_add_item(subtree, hf_nmea0183_unknown_field,
1163                                              tvb, offset, end_of_field_offset - offset, ENC_ASCII);
1164         if (end_of_field_offset - offset == 0)
1165         {
1166             proto_item_append_text(ti, "[empty]");
1167         }
1168         offset = end_of_field_offset + 1;
1169     }
1170     return tvb_captured_length(tvb);
1171 }
1172
1173 static int
1174 dissect_nmea0183(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
1175 {
1176     int offset = 0;
1177     int start_checksum_offset = 0;
1178     const uint8_t *talker_id = NULL;
1179     const uint8_t *sentence_id = NULL;
1180     const uint8_t *checksum = NULL;
1181
1182     col_set_str(pinfo->cinfo, COL_PROTOCOL, "NMEA 0183");
1183     /* Clear the info column */
1184     col_clear(pinfo->cinfo, COL_INFO);
1185
1186     proto_item *ti = proto_tree_add_item(tree, proto_nmea0183, tvb, 0, -1, ENC_NA);
1187     proto_tree *nmea0183_tree = proto_item_add_subtree(ti, ett_nmea0183);
1188
1189     /* Start delimiter */
1190     if (tvb_get_uint8(tvb, offset) != '$')
1191     {
1192         expert_add_info(pinfo, nmea0183_tree, &ei_nmea0183_invalid_first_character);
1193     }
1194     offset += 1;
1195
1196     /* Talker id */
1197     ti = proto_tree_add_item_ret_string(nmea0183_tree, hf_nmea0183_talker_id,
1198                                         tvb, offset, 2, ENC_ASCII,
1199                                         pinfo->pool, &talker_id);
1200
1201     proto_item_append_text(ti, " (%s)", str_to_str(talker_id, known_talker_ids, "Unknown talker ID"));
1202
1203     col_append_fstr(pinfo->cinfo, COL_INFO, "Talker %s", talker_id);
1204
1205     offset += 2;
1206
1207     /* Sentence id */
1208     ti = proto_tree_add_item_ret_string(nmea0183_tree, hf_nmea0183_sentence_id,
1209                                         tvb, offset, 3, ENC_ASCII,
1210                                         pinfo->pool, &sentence_id);
1211
1212     proto_item_append_text(ti, " (%s)", str_to_str(sentence_id, known_sentence_ids, "Unknown sentence ID"));
1213
1214     col_append_fstr(pinfo->cinfo, COL_INFO, ", Sentence %s", sentence_id);
1215
1216     offset += 3;
1217
1218     /* Start of checksum */
1219     start_checksum_offset = tvb_find_uint8(tvb, offset, -1, '*');
1220     if (start_checksum_offset == -1)
1221     {
1222         expert_add_info(pinfo, nmea0183_tree, &ei_nmea0183_missing_checksum_character);
1223         return tvb_captured_length(tvb);
1224     }
1225
1226     /* Data */
1227     offset += 1;
1228     tvbuff_t *data_tvb = tvb_new_subset_length(tvb, offset, start_checksum_offset - offset);
1229     if (g_ascii_strcasecmp(sentence_id, "DPT") == 0)
1230     {
1231         offset += dissect_nmea0183_sentence_dpt(data_tvb, pinfo, nmea0183_tree);
1232     }
1233     else if (g_ascii_strcasecmp(sentence_id, "GGA") == 0)
1234     {
1235         offset += dissect_nmea0183_sentence_gga(data_tvb, pinfo, nmea0183_tree);
1236     }
1237     else if (g_ascii_strcasecmp(sentence_id, "GLL") == 0)
1238     {
1239         offset += dissect_nmea0183_sentence_gll(data_tvb, pinfo, nmea0183_tree);
1240     }
1241     else if (g_ascii_strcasecmp(sentence_id, "GST") == 0)
1242     {
1243         offset += dissect_nmea0183_sentence_gst(data_tvb, pinfo, nmea0183_tree);
1244     }
1245     else if (g_ascii_strcasecmp(sentence_id, "HDT") == 0)
1246     {
1247         offset += dissect_nmea0183_sentence_hdt(data_tvb, pinfo, nmea0183_tree);
1248     }
1249     else if (g_ascii_strcasecmp(sentence_id, "ROT") == 0)
1250     {
1251         offset += dissect_nmea0183_sentence_rot(data_tvb, pinfo, nmea0183_tree);
1252     }
1253     else if (g_ascii_strcasecmp(sentence_id, "VBW") == 0)
1254     {
1255         offset += dissect_nmea0183_sentence_vbw(data_tvb, pinfo, nmea0183_tree);
1256     }
1257     else if (g_ascii_strcasecmp(sentence_id, "VHW") == 0)
1258     {
1259         offset += dissect_nmea0183_sentence_vhw(data_tvb, pinfo, nmea0183_tree);
1260     }
1261     else if (g_ascii_strcasecmp(sentence_id, "VLW") == 0)
1262     {
1263         offset += dissect_nmea0183_sentence_vlw(data_tvb, pinfo, nmea0183_tree);
1264     }
1265     else if (g_ascii_strcasecmp(sentence_id, "VTG") == 0)
1266     {
1267         offset += dissect_nmea0183_sentence_vtg(data_tvb, pinfo, nmea0183_tree);
1268     }
1269     else if (g_ascii_strcasecmp(sentence_id, "ZDA") == 0)
1270     {
1271         offset += dissect_nmea0183_sentence_zda(data_tvb, pinfo, nmea0183_tree);
1272     }
1273     else
1274     {
1275         offset += dissect_nmea0183_sentence_unknown(data_tvb, pinfo, nmea0183_tree);
1276     }
1277
1278     /* Checksum */
1279     offset += 1;
1280     ti = proto_tree_add_item_ret_string(nmea0183_tree, hf_nmea0183_checksum,
1281                                         tvb, offset, 2, ENC_ASCII,
1282                                         pinfo->pool, &checksum);
1283
1284     uint8_t received_checksum = (uint8_t)strtol(checksum, NULL, 16);
1285     uint8_t calculated_checksum = calculate_checksum(tvb, 1, offset - 2);
1286     if (received_checksum == calculated_checksum)
1287     {
1288         proto_item_append_text(ti, " [correct]");
1289     }
1290     else
1291     {
1292         proto_item_append_text(ti, " [INCORRECT]");
1293         expert_add_info(pinfo, ti, &ei_nmea0183_checksum_incorrect);
1294     }
1295
1296     // Calculated checksum highlights 2 bytes, which is the ascii hex value of a 1 byte checksum
1297     proto_item *checksum_tree = proto_item_add_subtree(ti, ett_nmea0183_checksum);
1298     ti = proto_tree_add_uint(checksum_tree, hf_nmea0183_checksum_calculated,
1299                              tvb, offset, 2, calculated_checksum);
1300     proto_item_set_generated(ti);
1301
1302     offset += 2;
1303
1304     /* End of line */
1305     if (tvb_captured_length_remaining(tvb, offset) < 2 ||
1306         tvb_get_uint8(tvb, offset) != '\r' ||
1307         tvb_get_uint8(tvb, offset + 1) != '\n')
1308     {
1309         expert_add_info(pinfo, nmea0183_tree, &ei_nmea0183_invalid_end_of_line);
1310     }
1311     offset += 2;
1312
1313     /* Check sentence length */
1314     if (offset > 82)
1315     {
1316         expert_add_info(pinfo, nmea0183_tree, &ei_nmea0183_sentence_too_long);
1317     }
1318
1319     return tvb_captured_length(tvb);
1320 }
1321
1322 void proto_register_nmea0183(void)
1323 {
1324     expert_module_t *expert_nmea0183;
1325
1326     static hf_register_info hf[] = {
1327         {&hf_nmea0183_talker_id,
1328          {"Talker ID", "nmea0183.talker",
1329           FT_STRING, BASE_NONE,
1330           NULL, 0x0,
1331           NULL, HFILL}},
1332         {&hf_nmea0183_sentence_id,
1333          {"Sentence ID", "nmea0183.sentence",
1334           FT_STRING, BASE_NONE,
1335           NULL, 0x0,
1336           NULL, HFILL}},
1337         {&hf_nmea0183_unknown_field,
1338          {"Field", "nmea0183.unknown_field",
1339           FT_STRING, BASE_NONE,
1340           NULL, 0x0,
1341           "NMEA 0183 Unknown field", HFILL}},
1342         {&hf_nmea0183_checksum,
1343          {"Checksum", "nmea0183.checksum",
1344           FT_STRING, BASE_NONE,
1345           NULL, 0x0,
1346           NULL, HFILL}},
1347         {&hf_nmea0183_checksum_calculated,
1348          {"Calculated checksum", "nmea0183.checksum_calculated",
1349           FT_UINT8, BASE_HEX,
1350           NULL, 0x0,
1351           NULL, HFILL}},
1352         {&hf_nmea0183_dpt_depth,
1353          {"Water depth", "nmea0183.dpt_depth",
1354           FT_STRING, BASE_NONE,
1355           NULL, 0x0,
1356           "NMEA 0183 DPT Water depth relative to transducer", HFILL}},
1357         {&hf_nmea0183_dpt_offset,
1358          {"Offset", "nmea0183.dpt_offset",
1359           FT_STRING, BASE_NONE,
1360           NULL, 0x0,
1361           "NMEA 0183 DPT Offset from transducer, positive means distance from transducer to water line, negative means distance from transducer to keel", HFILL}},
1362         {&hf_nmea0183_dpt_max_range,
1363          {"Maximum range", "nmea0183.dpt_max_range",
1364           FT_STRING, BASE_NONE,
1365           NULL, 0x0,
1366           "NMEA 0183 DPT Maximum range scale in use (NMEA 3.0 and above)", HFILL}},
1367         {&hf_nmea0183_gga_time,
1368          {"UTC Time of position", "nmea0183.gga_time",
1369           FT_NONE, BASE_NONE,
1370           NULL, 0x0,
1371           NULL, HFILL}},
1372         {&hf_nmea0183_gga_time_hour,
1373          {"Hour", "nmea0183.gga_time_hour",
1374           FT_STRING, BASE_NONE,
1375           NULL, 0x0,
1376           NULL, HFILL}},
1377         {&hf_nmea0183_gga_time_minute,
1378          {"Minute", "nmea0183.gga_time_minute",
1379           FT_STRING, BASE_NONE,
1380           NULL, 0x0,
1381           NULL, HFILL}},
1382         {&hf_nmea0183_gga_time_second,
1383          {"Second", "nmea0183.gga_time_second",
1384           FT_STRING, BASE_NONE,
1385           NULL, 0x0,
1386           NULL, HFILL}},
1387         {&hf_nmea0183_gga_latitude,
1388          {"Latitude", "nmea0183.gga_latitude",
1389           FT_NONE, BASE_NONE,
1390           NULL, 0x0,
1391           NULL, HFILL}},
1392         {&hf_nmea0183_gga_latitude_degree,
1393          {"Degree", "nmea0183.gga_latitude_degree",
1394           FT_STRING, BASE_NONE,
1395           NULL, 0x0,
1396           NULL, HFILL}},
1397         {&hf_nmea0183_gga_latitude_minute,
1398          {"Minute", "nmea0183.gga_latitude_minute",
1399           FT_STRING, BASE_NONE,
1400           NULL, 0x0,
1401           NULL, HFILL}},
1402         {&hf_nmea0183_gga_latitude_direction,
1403          {"Direction", "nmea0183.gga_latitude_direction",
1404           FT_STRING, BASE_NONE,
1405           NULL, 0x0,
1406           NULL, HFILL}},
1407         {&hf_nmea0183_gga_longitude,
1408          {"Longitude", "nmea0183.gga_longitude",
1409           FT_NONE, BASE_NONE,
1410           NULL, 0x0,
1411           NULL, HFILL}},
1412         {&hf_nmea0183_gga_longitude_degree,
1413          {"Degree", "nmea0183.gga_longitude_degree",
1414           FT_STRING, BASE_NONE,
1415           NULL, 0x0,
1416           NULL, HFILL}},
1417         {&hf_nmea0183_gga_longitude_minute,
1418          {"Minute", "nmea0183.gga_longitude_minute",
1419           FT_STRING, BASE_NONE,
1420           NULL, 0x0,
1421           NULL, HFILL}},
1422         {&hf_nmea0183_gga_longitude_direction,
1423          {"Direction", "nmea0183.gga_longitude_direction",
1424           FT_STRING, BASE_NONE,
1425           NULL, 0x0,
1426           NULL, HFILL}},
1427         {&hf_nmea0183_gga_quality,
1428          {"Quality indicator", "nmea0183.gga_quality",
1429           FT_STRING, BASE_NONE,
1430           NULL, 0x0,
1431           NULL, HFILL}},
1432         {&hf_nmea0183_gga_number_satellites,
1433          {"Number of satellites", "nmea0183.gga_number_satellites",
1434           FT_STRING, BASE_NONE,
1435           NULL, 0x0,
1436           "NMEA 0183 GGA Number of satellites in use", HFILL}},
1437         {&hf_nmea0183_gga_horizontal_dilution,
1438          {"Horizontal Dilution", "nmea0183.gga_horizontal_dilution",
1439           FT_STRING, BASE_NONE,
1440           NULL, 0x0,
1441           "NMEA 0183 GGA Horizontal Dilution of precision", HFILL}},
1442         {&hf_nmea0183_gga_altitude,
1443          {"Altitude", "nmea0183.gga_altitude",
1444           FT_STRING, BASE_NONE,
1445           NULL, 0x0,
1446           "NMEA 0183 GGA Antenna Altitude above mean-sea-level", HFILL}},
1447         {&hf_nmea0183_gga_altitude_unit,
1448          {"Altitude unit", "nmea0183.gga_altitude_unit",
1449           FT_STRING, BASE_NONE,
1450           NULL, 0x0,
1451           "NMEA 0183 GGA Units of antenna altitude", HFILL}},
1452         {&hf_nmea0183_gga_geoidal_separation,
1453          {"Geoidal separation", "nmea0183.gga_geoidal_separation",
1454           FT_STRING, BASE_NONE,
1455           NULL, 0x0,
1456           "NMEA 0183 GGA Geoidal separation, the difference between the WGS-84 earth ellipsoid and mean-sea-level", HFILL}},
1457         {&hf_nmea0183_gga_geoidal_separation_unit,
1458          {"Geoidal separation unit", "nmea0183.gga_geoidal_separation_unit",
1459           FT_STRING, BASE_NONE,
1460           NULL, 0x0,
1461           "NMEA 0183 GGA Units of geoidal separation, meters", HFILL}},
1462         {&hf_nmea0183_gga_age_dgps,
1463          {"Age of differential GPS", "nmea0183.gga_age_dgps",
1464           FT_STRING, BASE_NONE,
1465           NULL, 0x0,
1466           NULL, HFILL}},
1467         {&hf_nmea0183_gga_dgps_station,
1468          {"Differential GPS station id", "nmea0183.gga_dgps_station",
1469           FT_STRING, BASE_NONE,
1470           NULL, 0x0,
1471           "NMEA 0183 GGA Differential reference station ID", HFILL}},
1472         {&hf_nmea0183_gll_latitude,
1473          {"Latitude", "nmea0183.gll_latitude",
1474           FT_NONE, BASE_NONE,
1475           NULL, 0x0,
1476           NULL, HFILL}},
1477         {&hf_nmea0183_gll_latitude_degree,
1478          {"Degree", "nmea0183.gll_latitude_degree",
1479           FT_STRING, BASE_NONE,
1480           NULL, 0x0,
1481           NULL, HFILL}},
1482         {&hf_nmea0183_gll_latitude_minute,
1483          {"Minute", "nmea0183.gll_latitude_minute",
1484           FT_STRING, BASE_NONE,
1485           NULL, 0x0,
1486           NULL, HFILL}},
1487         {&hf_nmea0183_gll_latitude_direction,
1488          {"Direction", "nmea0183.gll_latitude_direction",
1489           FT_STRING, BASE_NONE,
1490           NULL, 0x0,
1491           NULL, HFILL}},
1492         {&hf_nmea0183_gll_longitude,
1493          {"Longitude", "nmea0183.gll_longitude",
1494           FT_NONE, BASE_NONE,
1495           NULL, 0x0,
1496           NULL, HFILL}},
1497         {&hf_nmea0183_gll_longitude_degree,
1498          {"Degree", "nmea0183.gll_longitude_degree",
1499           FT_STRING, BASE_NONE,
1500           NULL, 0x0,
1501           NULL, HFILL}},
1502         {&hf_nmea0183_gll_longitude_minute,
1503          {"Minute", "nmea0183.gll_longitude_minute",
1504           FT_STRING, BASE_NONE,
1505           NULL, 0x0,
1506           NULL, HFILL}},
1507         {&hf_nmea0183_gll_longitude_direction,
1508          {"Direction", "nmea0183.gll_longitude_direction",
1509           FT_STRING, BASE_NONE,
1510           NULL, 0x0,
1511           NULL, HFILL}},
1512         {&hf_nmea0183_gll_time,
1513          {"UTC Time of position", "nmea0183.gll_time",
1514           FT_NONE, BASE_NONE,
1515           NULL, 0x0,
1516           NULL, HFILL}},
1517         {&hf_nmea0183_gll_time_hour,
1518          {"Hour", "nmea0183.gll_time_hour",
1519           FT_STRING, BASE_NONE,
1520           NULL, 0x0,
1521           NULL, HFILL}},
1522         {&hf_nmea0183_gll_time_minute,
1523          {"Minute", "nmea0183.gll_time_minute",
1524           FT_STRING, BASE_NONE,
1525           NULL, 0x0,
1526           NULL, HFILL}},
1527         {&hf_nmea0183_gll_time_second,
1528          {"Second", "nmea0183.gll_time_second",
1529           FT_STRING, BASE_NONE,
1530           NULL, 0x0,
1531           NULL, HFILL}},
1532         {&hf_nmea0183_gll_status,
1533          {"Status", "nmea0183.gll_status",
1534           FT_STRING, BASE_NONE,
1535           NULL, 0x0,
1536           NULL, HFILL}},
1537         {&hf_nmea0183_gll_mode,
1538          {"FAA mode", "nmea0183.gll_mode",
1539           FT_STRING, BASE_NONE,
1540           NULL, 0x0,
1541           "NMEA 0183 GLL FAA mode indicator (NMEA 2.3 and later)", HFILL}},
1542         {&hf_nmea0183_gst_time,
1543          {"UTC Time of position", "nmea0183.gst_time",
1544           FT_NONE, BASE_NONE,
1545           NULL, 0x0,
1546           NULL, HFILL}},
1547         {&hf_nmea0183_gst_time_hour,
1548          {"Hour", "nmea0183.gst_time_hour",
1549           FT_STRING, BASE_NONE,
1550           NULL, 0x0,
1551           NULL, HFILL}},
1552         {&hf_nmea0183_gst_time_minute,
1553          {"Minute", "nmea0183.gst_time_minute",
1554           FT_STRING, BASE_NONE,
1555           NULL, 0x0,
1556           NULL, HFILL}},
1557         {&hf_nmea0183_gst_time_second,
1558          {"Second", "nmea0183.gst_time_second",
1559           FT_STRING, BASE_NONE,
1560           NULL, 0x0,
1561           NULL, HFILL}},
1562         {&hf_nmea0183_gst_rms_total_sd,
1563          {"Total RMS standard deviation", "nmea0183.gst_sd_rms_total",
1564           FT_STRING, BASE_NONE,
1565           NULL, 0x0,
1566           "NMEA 0183 GST Total RMS standard deviation of ranges inputs to the navigation solution", HFILL}},
1567         {&hf_nmea0183_gst_ellipse_major_sd,
1568          {"Standard deviation of semi-major axis of error", "nmea0183.gst_ellipse_major_sd",
1569           FT_STRING, BASE_NONE,
1570           NULL, 0x0,
1571           NULL, HFILL}},
1572         {&hf_nmea0183_gst_ellipse_minor_sd,
1573          {"Standard deviation of semi-minor axis of error ellipse", "nmea0183.gst_ellipse_minor_sd",
1574           FT_STRING, BASE_NONE,
1575           NULL, 0x0,
1576           NULL, HFILL}},
1577         {&hf_nmea0183_gst_ellipse_orientation,
1578          {"Orientation of semi-major axis of error ellipse", "nmea0183.gst_ellipse_orientation",
1579           FT_STRING, BASE_NONE,
1580           NULL, 0x0,
1581           "NMEA 0183 GST Orientation of semi-major axis of error ellipse (true north degrees)", HFILL}},
1582         {&hf_nmea0183_gst_latitude_sd,
1583          {"Standard deviation of latitude error", "nmea0183.gst_sd_latitude",
1584           FT_STRING, BASE_NONE,
1585           NULL, 0x0,
1586           NULL, HFILL}},
1587         {&hf_nmea0183_gst_longitude_sd,
1588          {"Standard deviation of longitude error", "nmea0183.gst_sd_longitude",
1589           FT_STRING, BASE_NONE,
1590           NULL, 0x0,
1591           NULL, HFILL}},
1592         {&hf_nmea0183_gst_altitude_sd,
1593          {"Standard deviation of altitude error", "nmea0183.gst_sd_altitude",
1594           FT_STRING, BASE_NONE,
1595           NULL, 0x0,
1596           NULL, HFILL}},
1597         {&hf_nmea0183_hdt_heading,
1598          {"True heading", "nmea0183.hdt_heading",
1599           FT_STRING, BASE_NONE,
1600           NULL, 0x0,
1601           NULL, HFILL}},
1602         {&hf_nmea0183_hdt_unit,
1603          {"Heading unit", "nmea0183.hdt_unit",
1604           FT_STRING, BASE_NONE,
1605           NULL, 0x0,
1606           "NMEA 0183 HDT Heading unit, must be T", HFILL}},
1607         {&hf_nmea0183_rot_rate_of_turn,
1608          {"Rate of turn", "nmea0183.rot_rate_of_turn",
1609           FT_STRING, BASE_NONE,
1610           NULL, 0x0,
1611           "NMEA 0183 ROT Rate Of Turn, degrees per minute, negative value means bow turns to port", HFILL}},
1612         {&hf_nmea0183_rot_valid,
1613          {"Validity", "nmea0183.rot_valid",
1614           FT_STRING, BASE_NONE,
1615           NULL, 0x0,
1616           "NMEA 0183 ROT Status, A means data is valid", HFILL}},
1617         {&hf_nmea0183_vbw_water_speed_longitudinal,
1618          {"Longitudinal water speed", "nmea0183.vbw_water_speed_longitudinal",
1619           FT_STRING, BASE_NONE,
1620           NULL, 0x0,
1621           "NMEA 0183 VBW Longitudinal water speed, negative value means astern, knots", HFILL}},
1622         {&hf_nmea0183_vbw_water_speed_transverse,
1623          {"Transverse water speed", "nmea0183.vbw_water_speed_transverse",
1624           FT_STRING, BASE_NONE,
1625           NULL, 0x0,
1626           "NMEA 0183 VBW Transverse water speed, negative value means port, knots", HFILL}},
1627         {&hf_nmea0183_vbw_water_speed_valid,
1628          {"Water speed validity", "nmea0183.vbw_water_speed_valid",
1629           FT_STRING, BASE_NONE,
1630           NULL, 0x0,
1631           "NMEA 0183 VBW Water speed status, A means data is valid", HFILL}},
1632         {&hf_nmea0183_vbw_ground_speed_longitudinal,
1633          {"Longitudinal ground speed", "nmea0183.vbw_ground_speed_longitudinal",
1634           FT_STRING, BASE_NONE,
1635           NULL, 0x0,
1636           "NMEA 0183 VBW Longitudinal ground speed, negative value means astern, knots", HFILL}},
1637         {&hf_nmea0183_vbw_ground_speed_transverse,
1638          {"Transverse ground speed", "nmea0183.vbw_ground_speed_transverse",
1639           FT_STRING, BASE_NONE,
1640           NULL, 0x0,
1641           "NMEA 0183 VBW Transverse ground speed, negative value means port, knots", HFILL}},
1642         {&hf_nmea0183_vbw_ground_speed_valid,
1643          {"Ground speed validity", "nmea0183.vbw_ground_speed_valid",
1644           FT_STRING, BASE_NONE,
1645           NULL, 0x0,
1646           "NMEA 0183 VBW Ground speed status, A means data is valid", HFILL}},
1647         {&hf_nmea0183_vbw_stern_water_speed,
1648          {"Stern water speed", "nmea0183.vbw_stern_water_speed",
1649           FT_STRING, BASE_NONE,
1650           NULL, 0x0,
1651           "NMEA 0183 VBW Stern traverse water ground speed, negative value means port, knots", HFILL}},
1652         {&hf_nmea0183_vbw_stern_water_speed_valid,
1653          {"Stern water speed validity", "nmea0183.vbw_stern_water_speed_valid",
1654           FT_STRING, BASE_NONE,
1655           NULL, 0x0,
1656           "NMEA 0183 VBW Stern traverse water speed status, A means data is valid", HFILL}},
1657         {&hf_nmea0183_vbw_stern_ground_speed,
1658          {"Stern ground speed", "nmea0183.vbw_stern_ground_speed",
1659           FT_STRING, BASE_NONE,
1660           NULL, 0x0,
1661           "NMEA 0183 VBW Stern traverse ground ground speed, negative value means port, knots", HFILL}},
1662         {&hf_nmea0183_vbw_stern_ground_speed_valid,
1663          {"Stern ground speed validity", "nmea0183.vbw_stern_ground_speed_valid",
1664           FT_STRING, BASE_NONE,
1665           NULL, 0x0,
1666           "NMEA 0183 VBW Stern traverse ground speed status, A means data is valid", HFILL}},
1667         {&hf_nmea0183_vhw_true_heading,
1668          {"True heading", "nmea0183.vhw_true_heading",
1669           FT_STRING, BASE_NONE,
1670           NULL, 0x0,
1671           NULL, HFILL}},
1672         {&hf_nmea0183_vhw_true_heading_unit,
1673          {"Heading unit", "nmea0183.vhw_true_heading_unit",
1674           FT_STRING, BASE_NONE,
1675           NULL, 0x0,
1676           "NMEA 0183 VHW Heading unit, must be T", HFILL}},
1677         {&hf_nmea0183_vhw_magnetic_heading,
1678          {"Magnetic heading", "nmea0183.vhw_magnetic_heading",
1679           FT_STRING, BASE_NONE,
1680           NULL, 0x0,
1681           NULL, HFILL}},
1682         {&hf_nmea0183_vhw_magnetic_heading_unit,
1683          {"Heading unit", "nmea0183.vhw_magnetic_heading_unit",
1684           FT_STRING, BASE_NONE,
1685           NULL, 0x0,
1686           "NMEA 0183 VHW Heading unit, must be M", HFILL}},
1687         {&hf_nmea0183_vhw_water_speed_knot,
1688          {"Water speed", "nmea0183.vhw_water_speed_knot",
1689           FT_STRING, BASE_NONE,
1690           NULL, 0x0,
1691           NULL, HFILL}},
1692         {&hf_nmea0183_vhw_water_speed_knot_unit,
1693          {"Speed unit", "nmea0183.vhw_water_speed_knot_unit",
1694           FT_STRING, BASE_NONE,
1695           NULL, 0x0,
1696           "NMEA 0183 VHW Water speed unit, must be N", HFILL}},
1697         {&hf_nmea0183_vhw_water_speed_kilometer,
1698          {"Water speed", "nmea0183.vhw_water_speed_kilometer",
1699           FT_STRING, BASE_NONE,
1700           NULL, 0x0,
1701           NULL, HFILL}},
1702         {&hf_nmea0183_vhw_water_speed_kilometer_unit,
1703          {"Speed unit", "nmea0183.vhw_water_speed_kilometer_unit",
1704           FT_STRING, BASE_NONE,
1705           NULL, 0x0,
1706           "NMEA 0183 VHW Water speed unit, must be K", HFILL}},
1707         {&hf_nmea0183_vlw_cumulative_water,
1708          {"Cumulative water distance", "nmea0183.vlw_hf_nmea0183_vlw_cumulative_water",
1709           FT_STRING, BASE_NONE,
1710           NULL, 0x0,
1711           "NMEA 0183 VLW Total cumulative water distance, nautical miles", HFILL}},
1712         {&hf_nmea0183_vlw_cumulative_water_unit,
1713          {"Distance unit", "nmea0183.vlw_cumulative_water_unit",
1714           FT_STRING, BASE_NONE,
1715           NULL, 0x0,
1716           "NMEA 0183 VLW Distance unit, must be N", HFILL}},
1717         {&hf_nmea0183_vlw_trip_water,
1718          {"Trip water distance", "nmea0183.vlw_hf_nmea0183_vlw_trip_water",
1719           FT_STRING, BASE_NONE,
1720           NULL, 0x0,
1721           "NMEA 0183 VLW Water distance since Reset, nautical miles", HFILL}},
1722         {&hf_nmea0183_vlw_trip_water_unit,
1723          {"Distance unit", "nmea0183.vlw_trip_water_unit",
1724           FT_STRING, BASE_NONE,
1725           NULL, 0x0,
1726           "NMEA 0183 VLW Distance unit, must be N", HFILL}},
1727         {&hf_nmea0183_vlw_cumulative_ground,
1728          {"Cumulative ground distance", "nmea0183.vlw_hf_nmea0183_vlw_cumulative_ground",
1729           FT_STRING, BASE_NONE,
1730           NULL, 0x0,
1731           "NMEA 0183 VLW Total cumulative ground distance, nautical miles (NMEA 3 and above)", HFILL}},
1732         {&hf_nmea0183_vlw_cumulative_ground_unit,
1733          {"Distance unit", "nmea0183.vlw_cumulative_ground_unit",
1734           FT_STRING, BASE_NONE,
1735           NULL, 0x0,
1736           "NMEA 0183 VLW Distance unit, must be N", HFILL}},
1737         {&hf_nmea0183_vlw_trip_ground,
1738          {"Trip ground distance", "nmea0183.vlw_hf_nmea0183_vlw_trip_ground",
1739           FT_STRING, BASE_NONE,
1740           NULL, 0x0,
1741           "NMEA 0183 VLW Ground distance since Reset, nautical miles (NMEA 3 and above)", HFILL}},
1742         {&hf_nmea0183_vlw_trip_ground_unit,
1743          {"Distance unit", "nmea0183.vlw_trip_ground_unit",
1744           FT_STRING, BASE_NONE,
1745           NULL, 0x0,
1746           "NMEA 0183 VLW Distance unit, must be N", HFILL}},
1747         {&hf_nmea0183_vtg_true_course,
1748          {"True course over ground", "nmea0183.vtg_true_course",
1749           FT_STRING, BASE_NONE,
1750           NULL, 0x0,
1751           NULL, HFILL}},
1752         {&hf_nmea0183_vtg_true_course_unit,
1753          {"Course unit", "nmea0183.vtg_true_course_unit",
1754           FT_STRING, BASE_NONE,
1755           NULL, 0x0,
1756           "NMEA 0183 VTG Course unit, must be T", HFILL}},
1757         {&hf_nmea0183_vtg_magnetic_course,
1758          {"Magnetic course over ground", "nmea0183.vtg_magnetic_course",
1759           FT_STRING, BASE_NONE,
1760           NULL, 0x0,
1761           NULL, HFILL}},
1762         {&hf_nmea0183_vtg_magnetic_course_unit,
1763          {"Course unit", "nmea0183.vtg_magnetic_course_unit",
1764           FT_STRING, BASE_NONE,
1765           NULL, 0x0,
1766           "NMEA 0183 VTG Course unit, must be M", HFILL}},
1767         {&hf_nmea0183_vtg_ground_speed_knot,
1768          {"Speed over ground", "nmea0183.vtg_ground_speed_knot",
1769           FT_STRING, BASE_NONE,
1770           NULL, 0x0,
1771           NULL, HFILL}},
1772         {&hf_nmea0183_vtg_ground_speed_knot_unit,
1773          {"Speed unit", "nmea0183.vtg_ground_speed_knot_unit",
1774           FT_STRING, BASE_NONE,
1775           NULL, 0x0,
1776           "NMEA 0183 VTG Ground speed unit, must be N", HFILL}},
1777         {&hf_nmea0183_vtg_ground_speed_kilometer,
1778          {"Speed over ground", "nmea0183.vtg_ground_speed_kilometer",
1779           FT_STRING, BASE_NONE,
1780           NULL, 0x0,
1781           NULL, HFILL}},
1782         {&hf_nmea0183_vtg_ground_speed_kilometer_unit,
1783          {"Speed unit", "nmea0183.vtg_ground_speed_kilometer_unit",
1784           FT_STRING, BASE_NONE,
1785           NULL, 0x0,
1786           "NMEA 0183 VTG Ground speed unit, must be K", HFILL}},
1787         {&hf_nmea0183_vtg_mode,
1788          {"FAA mode", "nmea0183.vtg_mode",
1789           FT_STRING, BASE_NONE,
1790           NULL, 0x0,
1791           "NMEA 0183 VTG FAA mode indicator (NMEA 2.3 and later)", HFILL}},
1792         {&hf_nmea0183_zda_time,
1793          {"UTC Time", "nmea0183.zda_time",
1794           FT_NONE, BASE_NONE,
1795           NULL, 0x0,
1796           NULL, HFILL}},
1797         {&hf_nmea0183_zda_time_hour,
1798          {"Hour", "nmea0183.zda_time_hour",
1799           FT_STRING, BASE_NONE,
1800           NULL, 0x0,
1801           NULL, HFILL}},
1802         {&hf_nmea0183_zda_time_minute,
1803          {"Minute", "nmea0183.zda_time_minute",
1804           FT_STRING, BASE_NONE,
1805           NULL, 0x0,
1806           NULL, HFILL}},
1807         {&hf_nmea0183_zda_time_second,
1808          {"Second", "nmea0183.zda_time_second",
1809           FT_STRING, BASE_NONE,
1810           NULL, 0x0,
1811           NULL, HFILL}},
1812         {&hf_nmea0183_zda_date_day,
1813          {"Day", "nmea0183.zda_date_day",
1814           FT_STRING, BASE_NONE,
1815           NULL, 0x0,
1816           NULL, HFILL}},
1817         {&hf_nmea0183_zda_date_month,
1818          {"Month", "nmea0183.zda_date_month",
1819           FT_STRING, BASE_NONE,
1820           NULL, 0x0,
1821           NULL, HFILL}},
1822         {&hf_nmea0183_zda_date_year,
1823          {"Year", "nmea0183.zda_date_year",
1824           FT_STRING, BASE_NONE,
1825           NULL, 0x0,
1826           NULL, HFILL}},
1827         {&hf_nmea0183_zda_local_zone_hour,
1828          {"Local zone hour", "nmea0183.zda_local_zone_hour",
1829           FT_STRING, BASE_NONE,
1830           NULL, 0x0,
1831           NULL, HFILL}},
1832         {&hf_nmea0183_zda_local_zone_minute,
1833          {"Local zone minute", "nmea0183.zda_local_zone_minute",
1834           FT_STRING, BASE_NONE,
1835           NULL, 0x0,
1836           NULL, HFILL}}};
1837
1838     /* Setup protocol subtree array */
1839     static int *ett[] = {
1840         &ett_nmea0183,
1841         &ett_nmea0183_checksum,
1842         &ett_nmea0183_sentence,
1843         &ett_nmea0183_zda_time,
1844         &ett_nmea0183_gga_time,
1845         &ett_nmea0183_gga_latitude,
1846         &ett_nmea0183_gga_longitude,
1847         &ett_nmea0183_gll_time,
1848         &ett_nmea0183_gll_latitude,
1849         &ett_nmea0183_gll_longitude,
1850         &ett_nmea0183_gst_time};
1851
1852     static ei_register_info ei[] = {
1853         {&ei_nmea0183_invalid_first_character,
1854          {"nmea0183.invalid_first_character", PI_PROTOCOL, PI_WARN,
1855           "First character should be '$'", EXPFILL}},
1856         {&ei_nmea0183_missing_checksum_character,
1857          {"nmea0183.missing_checksum_character", PI_MALFORMED, PI_ERROR,
1858           "Missing begin of checksum character '*'", EXPFILL}},
1859         {&ei_nmea0183_invalid_end_of_line,
1860          {"nmea0183.invalid_end_of_line", PI_PROTOCOL, PI_WARN,
1861           "Sentence should end with <CR><LF>", EXPFILL}},
1862         {&ei_nmea0183_checksum_incorrect,
1863          {"nmea0183.checksum_incorrect", PI_CHECKSUM, PI_WARN,
1864           "Incorrect checksum", EXPFILL}},
1865         {&ei_nmea0183_sentence_too_long,
1866          {"nmea0183.sentence_too_long", PI_PROTOCOL, PI_WARN,
1867           "Sentence is too long. Maximum is 82 bytes including $ and <CR><LF>", EXPFILL}},
1868         {&ei_nmea0183_field_time_too_short,
1869          {"nmea0183.field_time_too_short", PI_PROTOCOL, PI_WARN,
1870           "Field containing time is too short. Field should be at least 6 characters", EXPFILL}},
1871         {&ei_nmea0183_field_latitude_too_short,
1872          {"nmea0183.field_latitude_too_short", PI_PROTOCOL, PI_WARN,
1873           "Field containing latitude is too short. Field should be at least 4 characters", EXPFILL}},
1874         {&ei_nmea0183_field_longitude_too_short,
1875          {"nmea0183.field_longitude_too_short", PI_PROTOCOL, PI_WARN,
1876           "Field containing longitude is too short. Field should be at least 5 characters", EXPFILL}},
1877         {&ei_nmea0183_field_missing,
1878          {"nmea0183.field_missing", PI_PROTOCOL, PI_WARN,
1879           "Field expected, but not found", EXPFILL}},
1880         {&ei_nmea0183_gga_altitude_unit_incorrect,
1881          {"nmea0183.gga_altitude_unit_incorrect", PI_PROTOCOL, PI_WARN,
1882           "Incorrect altitude unit (should be 'M')", EXPFILL}},
1883         {&ei_nmea0183_gga_geoidal_separation_unit_incorrect,
1884          {"nmea0183.gga_geoidal_separation_unit_incorrect", PI_PROTOCOL, PI_WARN,
1885           "Incorrect geoidal separation unit (should be 'M')", EXPFILL}},
1886         {&ei_nmea0183_hdt_unit_incorrect,
1887          {"nmea0183.hdt_unit_incorrect", PI_PROTOCOL, PI_WARN,
1888           "Incorrect heading unit (should be 'T')", EXPFILL}},
1889         {&ei_nmea0183_vhw_true_heading_unit_incorrect,
1890          {"nmea0183.vhw_true_heading_unit_incorrect", PI_PROTOCOL, PI_WARN,
1891           "Incorrect heading unit (should be 'T')", EXPFILL}},
1892         {&ei_nmea0183_vhw_magnetic_heading_unit_incorrect,
1893          {"nmea0183.vhw_magnetic_heading_unit_incorrect", PI_PROTOCOL, PI_WARN,
1894           "Incorrect heading unit (should be 'M')", EXPFILL}},
1895         {&ei_nmea0183_vhw_water_speed_knot_unit_incorrect,
1896          {"nmea0183.vhw_water_speed_knot_unit_incorrect", PI_PROTOCOL, PI_WARN,
1897           "Incorrect speed unit (should be 'N')", EXPFILL}},
1898         {&ei_nmea0183_vhw_water_speed_kilometer_unit_incorrect,
1899          {"nmea0183.vhw_water_speed_kilometer_unit_incorrect", PI_PROTOCOL, PI_WARN,
1900           "Incorrect speed unit (should be 'K')", EXPFILL}},
1901         {&ei_nmea0183_vlw_cumulative_water_unit_incorrect,
1902          {"nmea0183.vlw_cumulative_water_unit_incorrect", PI_PROTOCOL, PI_WARN,
1903           "Incorrect distance unit (should be 'N')", EXPFILL}},
1904         {&ei_nmea0183_vlw_trip_water_unit_incorrect,
1905          {"nmea0183.vlw_trip_water_unit_incorrect", PI_PROTOCOL, PI_WARN,
1906           "Incorrect distance unit (should be 'N')", EXPFILL}},
1907         {&ei_nmea0183_vlw_cumulative_ground_unit_incorrect,
1908          {"nmea0183.vlw_cumulative_ground_unit_incorrect", PI_PROTOCOL, PI_WARN,
1909           "Incorrect distance unit (should be 'N')", EXPFILL}},
1910         {&ei_nmea0183_vlw_trip_ground_unit_incorrect,
1911          {"nmea0183.vlw_trip_ground_unit_incorrect", PI_PROTOCOL, PI_WARN,
1912           "Incorrect distance unit (should be 'N')", EXPFILL}},
1913         {&ei_nmea0183_vtg_true_course_unit_incorrect,
1914          {"nmea0183.vtg_true_course_unit_incorrect", PI_PROTOCOL, PI_WARN,
1915           "Incorrect course unit (should be 'T')", EXPFILL}},
1916         {&ei_nmea0183_vtg_magnetic_course_unit_incorrect,
1917          {"nmea0183.vtg_magnetic_course_unit_incorrect", PI_PROTOCOL, PI_WARN,
1918           "Incorrect course unit (should be 'M')", EXPFILL}},
1919         {&ei_nmea0183_vtg_ground_speed_knot_unit_incorrect,
1920          {"nmea0183.vtg_ground_speed_knot_unit_incorrect", PI_PROTOCOL, PI_WARN,
1921           "Incorrect speed unit (should be 'N')", EXPFILL}},
1922         {&ei_nmea0183_vtg_ground_speed_kilometer_unit_incorrect,
1923          {"nmea0183.vtg_ground_speed_kilometer_unit_incorrect", PI_PROTOCOL, PI_WARN,
1924           "Incorrect speed unit (should be 'K')", EXPFILL}}};
1925
1926     proto_nmea0183 = proto_register_protocol("NMEA 0183 protocol", "NMEA 0183", "nmea0183");
1927
1928     proto_register_field_array(proto_nmea0183, hf, array_length(hf));
1929     proto_register_subtree_array(ett, array_length(ett));
1930     expert_nmea0183 = expert_register_protocol(proto_nmea0183);
1931     expert_register_field_array(expert_nmea0183, ei, array_length(ei));
1932
1933     nmea0183_handle = register_dissector("nmea0183", dissect_nmea0183, proto_nmea0183);
1934 }
1935
1936 void proto_reg_handoff_nmea0183(void)
1937 {
1938     dissector_add_for_decode_as_with_preference("udp.port", nmea0183_handle);
1939 }