'\" t
.\"     Title: gpsdecode
.\"    Author: Eric S. Raymond
.\" Generator: Asciidoctor 2.0.20
.\"      Date: 2023-01-10
.\"    Manual: GPSD Documentation
.\"    Source: GPSD, Version 3.25
.\"  Language: English
.\"
.TH "GPSDECODE" "1" "2023-01-10" "GPSD, Version 3.25" "GPSD Documentation"
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.SH "NAME"
gpsdecode \- decode GPS, RTCM or AIS streams into a readable format
.SH "SYNOPSIS"
.sp
\fBgpsdecode\fP [OPTIONS]
.sp
\fBgpsdecode\fP \-h
.sp
\fBgpsdecode\fP \-V
.SH "DESCRIPTION"
.sp
\fBgpsdecode\fP 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 \fBgpsd\fP; this
tool uses the same decoding logic as \fBgpsd\fP, but with a simpler interface
intended for batch processing of data files.
.sp
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 \fBgpsd\fP(8) for
applicable standards and known limitations of the decoding logic.
.sp
You can use this tool with \fBnc\fP(1) to examine AIS feeds from AIS pooling
services, RTCM feeds from RTCM receivers or NTRIP broadcasters.
.SH "OPTIONS"
.sp
\fB\-?\fP, \fB\-h\fP, \fB\-\-help\fP
.RS 4
Output a usage mssage, then exit.
.RE
.sp
\fB\-c\fP, \fB\-\-json\fP
.RS 4
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 (\fB\-u\fP is forced). Strings are unpacked from six\-bit
to full ASCII
.RE
.sp
\fB\-d\fP, \fB\-\-decode\fP
.RS 4
Decode packets presented on standard input to standard output. This is
the default behavior.
.RE
.sp
\fB\-D LVL\fP, \fB\-\-debug LVL\fP
.RS 4
Set the debug verbosity level to LVL. It is mainly of interest to for
troubleshooting.
.RE
.sp
\fB\-e\fP, \fB\-\-encode\fP
.RS 4
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.
.RE
.sp
\fB\-j\fP, \fB\-\-json\fP
.RS 4
Sets the output dump format to JSON (the default behavior).
.RE
.sp
\fB\-m\fP, \fB\-\-minlength\fP
.RS 4
Dump minimum lengths for each packet type in the input (ignoring
comment packets). This is probably of interest only to GSD developers.
.RE
.sp
\fB\-n\fP, \fB\-\-nmea\fP
.RS 4
Dump the generated pseudo\-NME0183.
.RE
.sp
\fB\-s\fP, \fB\-\-split24\fP
.RS 4
Report AIS Type 24 sentence halves separately rather than attempting
to aggregate them.
.RE
.sp
\fB\-t TYPES\fP, \fB\-\-types TYPES\fP
.RS 4
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.
.RE
.sp
\fB\-u\fP, \fB\-\-unsscaled\fP
.RS 4
Suppress scaling of AIS data to float quantities and text expansion of
numeric codes. A dump with this option is lossless.
.RE
.sp
\fB\-v\fP, \fB\-\-verbose\fP
.RS 4
Dump textual packets to output as they are received on input,
immediately preceding corresponding output.
.RE
.sp
\fB\-V\fP, \fB\-\-version\fP
.RS 4
Print version number, then exit.
.RE
.SH "AIS DSV FORMAT"
.sp
With the \fB\-c\fP or \fB\-\-ais\fP 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.
.SH "RETURN VALUES"
.sp
\fB0\fP
.RS 4
on success.
.RE
.sp
\fB1\fP
.RS 4
if the action was unknown or the write to the control socket failed,
.RE
.SH "SEE ALSO"
.sp
\fBgpsd\fP(8), \fBgps\fP(1)
.SH "RESOURCES"
.sp
\fBProject web site:\fP \c
.URL "https://gpsd.io/" "" ""
.SH "COPYING"
.sp
This file is Copyright 2013 by the GPSD project
.br
SPDX\-License\-Identifier: BSD\-2\-clause
.SH "AUTHOR"
.sp
Eric S. Raymond