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GPSDECODE(1)                  GPSD Documentation                  GPSDECODE(1)

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

SYNOPSIS
       gpsdecode [-c] [-d] [-e] [-j] [-m] [-n] [-s] [-t typelist] [-u] [-v]
                 [-D debuglevel] [-V]

DESCRIPTION
       This 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 in gpsd(8); 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
       The -d option tells the program to decode packets presented on standard
       input to standard output. This is the default behavior.

       The -j explicitly sets the output dump format to JSON (the default
       behavior).

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

       The -n enables dumping in generated pseudo-NME0183.

       The -e option option tells the program to 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.

       The -s option option tells the program to report AIS Type 24 sentence
       halves separately rather than attempting to aggregate them.

       The -t accepts 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.

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

       The -v enables dumping of textual packets to output as they are
       received on input, immediately preceding corresponding output.

       The -c 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

       The -V option directs the program to emit its version number, then
       exit.

       The -D option sets a debug verbosity level. It is mainly of interest to
       developers.

AIS DSV FORMAT
       With the -c 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.

SEE ALSO
       gpsd(8), gpsctl(1), gpsdctl(8), gps(1), libgps(3), libgpsd(3),
       gpsprof(1), gpsfake(1),

AUTHOR
       Eric S. Raymond esr@thyrsus.com.

The GPSD Project                  13 Jul 2005                     GPSDECODE(1)