NAME

       gpsdecode - decode GPS, RTCM or AIS streams into a readable format

SYNOPSIS

       gpsdecode [OPTIONS]

       gpsdecode -h

       gpsdecode -V

DESCRIPTION

       gpsdecode tool is a batch-mode decoder for NMEA and various binary packet formats
       associated with GPS, AIS, and differential-correction services. It produces a JSON dump on
       standard output from binary on standard input. The JSON is the same format documented by
       gpsd; this tool uses the same decoding logic as gpsd, but with a simpler interface
       intended for batch processing of data files.

       All sensor-input formats known to the GPSD project can be decoded by this tool. These
       include: NMEA, AIVDM (the NMEA-derived sentence format used by AIS, the marine Automatic
       Identification System), RTCM2, and all supported GPS binary formats (notably including
       SiRF). See gpsd(8) for applicable standards and known limitations of the decoding logic.

       You can use this tool with nc(1) to examine AIS feeds from AIS pooling services, RTCM
       feeds from RTCM receivers or NTRIP broadcasters.

OPTIONS

       -?, -h, --help
           Output a usage mssage, then exit.

       -c, --json
           Sets the AIS dump format to separate fields with an ASCII pipe symbol. Fields are
           dumped in the order they occur in the AIS packet. Numerics are not scaled (-u is
           forced). Strings are unpacked from six-bit to full ASCII

       -d, --decode
           Decode packets presented on standard input to standard output. This is the default
           behavior.

       -D LVL, --debug LVL
           Set the debug verbosity level to LVL. It is mainly of interest to for troubleshooting.

       -e, --encode
           Encode JSON on standard input to JSON on standard output. This option is only useful
           for regression-testing of the JSON dumping and parsing code.

       -j, --json
           Sets the output dump format to JSON (the default behavior).

       -m, --minlength
           Dump minimum lengths for each packet type in the input (ignoring comment packets).
           This is probably of interest only to GSD developers.

       -n, --nmea
           Dump the generated pseudo-NME0183.

       -s, --split24
           Report AIS Type 24 sentence halves separately rather than attempting to aggregate
           them.

       -t TYPES, --types TYPES
           A comma-separated list of numeric types. Packets with a numeric AIS, RTCM2, or RTCM3
           type are passed through and output only if they match a type in the list. Packets of
           other kinds (in particular GPS packets) are passed through unconditionally.

       -u, --unsscaled
           Suppress scaling of AIS data to float quantities and text expansion of numeric codes.
           A dump with this option is lossless.

       -v, --verbose
           Dump textual packets to output as they are received on input, immediately preceding
           corresponding output.

       -V, --version
           Print version number, then exit.

AIS DSV FORMAT

       With the -c or --ais option, dump lines are values of AIS payload fields, pipe-separated,
       in the order that they occur in the payload. Spans of fields expressing a date are emitted
       as an ISO8601 timestamp (look for colons and the trailing Z indicating Zulu/UTC time), and
       the 19-bit group of TDMA status fields found at the end of message types 1-4 are are
       dumped as a single unsigned integer (in hex preceded by "0x"). Unused regional-authority
       fields are also dumped (in hex preceded by "0x"). Variable-length binary fields are dumped
       as an integer bit length, followed by a colon, followed by a hex dump.

RETURN VALUES

       0
           on success.

       1
           if the action was unknown or the write to the control socket failed,

SEE ALSO

       gpsd(8), gps(1)

RESOURCES

       Project web site: https://gpsd.io/

COPYING

       This file is Copyright 2013 by the GPSD project
       SPDX-License-Identifier: BSD-2-clause

AUTHOR

       Eric S. Raymond