From daf596d2b37b8b19822315eea6aa34ebb0d18339 Mon Sep 17 00:00:00 2001 From: "Eric S. Raymond" Date: Fri, 13 Mar 2009 16:40:52 +0000 Subject: rtcmdecode -> gpsdecode. --- gpsdecode.xml | 149 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 gpsdecode.xml (limited to 'gpsdecode.xml') diff --git a/gpsdecode.xml b/gpsdecode.xml new file mode 100644 index 00000000..d1cbcd7c --- /dev/null +++ b/gpsdecode.xml @@ -0,0 +1,149 @@ + + + + +gpsdecode +1 +13 Jul 2005 + + +gpsdecode +decode RTCM or AIVDM streams into a readable format + + + + + gpsdecode + -d + -e + -v debuglevel + -V + + + +DESCRIPTION + +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. + +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 +nc1 +to examine RTCM feeds from DGPSIP servers or Ntrip broadcasters. The +decoder dump format for RTCM2 is described in +rtcm5; +these lines go to standard output. + +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. + + +OPTIONS + +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. + +RTCM2 will be dumped in the format of +rtcm-1045 +on standard output. + +The -e option option tells the program to encode a text dump in +the format of +rtcm-1045 +to standard output. Encoding is supported only RTCM2, not for +RTCM3. + +The -V option directs the program to emit its version number, +then exit. + +The -v option sets a verbosity level. It is mainly of interest +to developers. + + +APPLICABLE STANDARDS + +The applicable standard for V2 is RTCM Recommended +Standards for Differential NAVSTAR GPS Service RTCM Paper +194-93/SC 104-STD. + +Note that gpsdecode 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. + +The applicable standard for V3 is RTCM Standard +10403.1 for Differential GNSS Services - Version 3 RTCM +Paper 177-2006-SC104-STD. + +Ordering instructions for the RTCM standards are accessible from +the website of the Radio Technical +Commission for Maritime Services under "Publications". + +The applicable standard for AIVDM is 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,. A more +accessible description can be found onn the references page of the +GPSD project website. + + +BUGS AND LIMITATIONS + +AIDVM decoding presently only parses fields for the common +sentence types 1-5; other packet payloads are dumped as raw +hex. + +RTCM3 decoding is buggy and incomplete. + +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. + +The decoder logic is sufficiently convoluted to confuse some +compiler optimizers, notably in GCC 3.x at -O2, into generating bad +code. + + +SEE ALSO + +gpsd8, +gps1, +libgps3, +libgpsd3, +gpsprof1, +gpsfake1, +rtcm-1045. + + +AUTHOR + +Eric S. Raymond esr@thyrsus.com. This is a +somewhat hacked version of an RTCM decoder originally written by +Wolfgang Rupprecht. There is a project page for +gpsd here. + + + + + -- cgit v1.2.1