Provided by: gpsd-clients_3.22-4ubuntu2_amd64 
NAME
gpsdecode - decode GPS, RTCM or AIS streams into a readable format
SYNOPSIS
gpsdecode [-?] [--ais] [--decode] [--debug LVL] [--encode] [--help] [--json] [--minlength] [--nmea]
[--split24] [--types typelist] [--unscaled] [--verbose] [--version] [-c] [-d] [-D LVL] [-e]
[-h] [-j] [-m] [-n] [-s] [-t typelist] [-u] [-v] [-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
-?, -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, --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.
SEE ALSO
gpsd(8), gpsctl(1), gpsdctl(8), gps(1), libgps(3), libgpsmm(3), gpsprof(1), gpsfake(1),
AUTHOR
Eric S. Raymond <esr@thyrsus.com>.