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author | Eric S. Raymond <esr@thyrsus.com> | 2009-03-13 16:40:52 +0000 |
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committer | Eric S. Raymond <esr@thyrsus.com> | 2009-03-13 16:40:52 +0000 |
commit | daf596d2b37b8b19822315eea6aa34ebb0d18339 (patch) | |
tree | ec1c35400dbbe0e920380b4150ed6c888749ea1c /gpsdecode.xml | |
parent | ef53d3a73bab5c9d031ecb091d847bee1d431703 (diff) | |
download | gpsd-daf596d2b37b8b19822315eea6aa34ebb0d18339.tar.gz |
rtcmdecode -> gpsdecode.
Diffstat (limited to 'gpsdecode.xml')
-rw-r--r-- | gpsdecode.xml | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/gpsdecode.xml b/gpsdecode.xml new file mode 100644 index 00000000..d1cbcd7c --- /dev/null +++ b/gpsdecode.xml @@ -0,0 +1,149 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE refentry PUBLIC + "-//OASIS//DTD DocBook XML V4.1.2//EN" + "docbook/docbookx.dtd"> +<refentry id='gpsdecode.1'> +<refmeta> +<refentrytitle>gpsdecode</refentrytitle> +<manvolnum>1</manvolnum> +<refmiscinfo class='date'>13 Jul 2005</refmiscinfo> +</refmeta> +<refnamediv id='name'> +<refname>gpsdecode</refname> +<refpurpose>decode RTCM or AIVDM streams into a readable format</refpurpose> +</refnamediv> +<refsynopsisdiv id='synopsis'> + +<cmdsynopsis> + <command>gpsdecode</command> + <arg choice='opt'>-d</arg> + <arg choice='opt'>-e</arg> + <arg choice='opt'>-v <replaceable>debuglevel</replaceable></arg> + <arg choice='opt'>-V</arg> +</cmdsynopsis> +</refsynopsisdiv> + +<refsect1 id='description'><title>DESCRIPTION</title> + +<para>This tool is a decoder/encoder for various binary packet formats +associated with GPS and differential-correction services. It produces +a text dump on standard output from binary on standard input, or +binary packets on standard output from text on standard input, and +aims to be 100% information-preserving in both directions. As well as +data, the decoder also prints decoder status messages to standard +error as necessary.</para> + +<para>Two of the supported formats are RTCM 2 and 3, a pair of obscure +and complicated serial protocol used for broadcasting pseudorange +corrections from differential-GPS reference stations. You can use this +mode of the tool with +<citerefentry><refentrytitle>nc</refentrytitle><manvolnum>1</manvolnum></citerefentry> +to examine RTCM feeds from DGPSIP servers or Ntrip broadcasters. The +decoder dump format for RTCM2 is described in +<citerefentry><refentrytitle>rtcm</refentrytitle><manvolnum>5</manvolnum></citerefentry>; +these lines go to standard output.</para> + +<para>Another supported format is AIVDM. This is the sentence format +used by the marine Automatic Identification System. This can be +decoded, but not yet encoded. The dump lines are unscaled integral +values of AIS packet fields, colon-separated, in the order that they +occur in the packet, except that the 19-bit TDMA status fields found +at the end of message types 1-4 are are dumped as a single unsigned +integer.</para> + +</refsect1> +<refsect1 id='options'><title>OPTIONS</title> + +<para>The -d option tells the program to decode packets presented on +standard input to a text dump on standard output. This is the default +behavior.</para> + +<para>RTCM2 will be dumped in the format of +<citerefentry><refentrytitle>rtcm-104</refentrytitle><manvolnum>5</manvolnum></citerefentry> +on standard output. </para> + +<para>The -e option option tells the program to encode a text dump in +the format of +<citerefentry><refentrytitle>rtcm-104</refentrytitle><manvolnum>5</manvolnum></citerefentry> +to standard output. Encoding is supported only RTCM2, not for +RTCM3.</para> + +<para>The -V option directs the program to emit its version number, +then exit.</para> + +<para>The -v option sets a verbosity level. It is mainly of interest +to developers.</para> + +</refsect1> +<refsect1 id='standard'><title>APPLICABLE STANDARDS</title> + +<para>The applicable standard for V2 is <citetitle>RTCM Recommended +Standards for Differential NAVSTAR GPS Service</citetitle> RTCM Paper +194-93/SC 104-STD.</para> + +<para>Note that <application>gpsdecode</application> presently +recognizes only the 2.1 level of RTCM; the protocol was revised up to +a version 2.3 including additional messages relating to GLONASS and +real-time kinematics before being deprecated in favor of V3. It is +now obsolete.</para> + +<para>The applicable standard for V3 is <citetitle>RTCM Standard +10403.1 for Differential GNSS Services - Version 3</citetitle> RTCM +Paper 177-2006-SC104-STD.</para> + +<para>Ordering instructions for the RTCM standards are accessible from +the website of the <ulink url='http://www.rtcm.org/'>Radio Technical +Commission for Maritime Services</ulink> under "Publications".</para> + +<para>The applicable standard for AIVDM is <citetitle>ITU-R M.1371: +ITU Recommendation on the Technical Characteristics for a Universal +Shipborne Automatic Identification System (AIS) using Time Division +Multiple Access in the Maritime Mobile Band</citetitle>,. A more +accessible description can be found onn the references page of the +GPSD project website.</para> + +</refsect1> +<refsect1 id='bugs'><title>BUGS AND LIMITATIONS</title> + +<para>AIDVM decoding presently only parses fields for the common +sentence types 1-5; other packet payloads are dumped as raw +hex.</para> + +<para>RTCM3 decoding is buggy and incomplete.</para> + +<para>RTCM2 represents floating-point quantities as an integer +multiple of a fixed scale factor. Editing an RTCM2 dump can +produce numbers that are not an integer multiple of the scale factor +for their field. If you do this, the value actually packed into +binary RTCM2 will be rounded down to the nearest scale unit, +and dumping will show slightly different numbers than those you +entered.</para> + +<para>The decoder logic is sufficiently convoluted to confuse some +compiler optimizers, notably in GCC 3.x at -O2, into generating bad +code.</para> + +</refsect1> +<refsect1 id='see_also'><title>SEE ALSO</title> +<para> +<citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>8</manvolnum></citerefentry>, +<citerefentry><refentrytitle>gps</refentrytitle><manvolnum>1</manvolnum></citerefentry>, +<citerefentry><refentrytitle>libgps</refentrytitle><manvolnum>3</manvolnum></citerefentry>, +<citerefentry><refentrytitle>libgpsd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, +<citerefentry><refentrytitle>gpsprof</refentrytitle><manvolnum>1</manvolnum></citerefentry>, +<citerefentry><refentrytitle>gpsfake</refentrytitle><manvolnum>1</manvolnum></citerefentry>, +<citerefentry><refentrytitle>rtcm-104</refentrytitle><manvolnum>5</manvolnum></citerefentry>. +</para> +</refsect1> +<refsect1 id='maintainer'><title>AUTHOR</title> + +<para>Eric S. Raymond <email>esr@thyrsus.com</email>. This is a +somewhat hacked version of an RTCM decoder originally written by +Wolfgang Rupprecht. There is a project page for +<application>gpsd</application> <ulink +url="http://gpsd.berlios.de/">here</ulink>.</para> + +</refsect1> + +</refentry> + |