GPSDECODE(1)                  GPSD Documentation                  GPSDECODE(1)

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

GPSD, Version 3.25                2023-01-10                      GPSDECODE(1)