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.TH "RTCMDECODE" 1 "" "" ""
.SH NAME
rtcmdecode \- decode RTCM104 streams into a readable format
.SH "SYNOPSIS"
.ad l
.hy 0
.HP 11
\fBrtcmdecode\fR [\-d] [\-e] [\-v\ \fIdebuglevel\fR]
.ad
.hy

.SH "DESCRIPTION"

.PP
This tool is a decoder for RTCM\-104, an obscure and complicated serial protocol used for broadcasting pseudorange corrections from differential\-GPS reference stations\&. RTCM\-104 is expected on standard input; an equivalent, 100%\-information\-preserving text format is written to standard output\&.

.PP
You can use this tool with \fBnc\fR(1) to examine RTCM feeds from DGPSIP servers\&.

.PP
The decoder dump format is described in \fBrtcm\fR(5); these lines go to standard output\&. As well as data the decoder also prints decoder status messages to standard error, as necessary\&.

.SH "OPTIONS"

.PP
The \-d option tells the program to decode RTCM\-104 presented on standard input to a text dump in the format of \fBrtcm\-104\fR(5) on standard output\&. This is the default behavior\&.

.PP
The \-e option option tells the program to encode a text dump in the format of \fBrtcm\-104\fR(5) to standard output\&.

.PP
The \-v option sets a verbosity level\&. It is mainly of interest to developers\&.

.SH "APPLICABLE STANDARDS"

.PP
The applicable standard is RTCM Recommended Standards for Differential NAVSTAR GPS Service RTCM Paper 194\-93/SC 104\-STD\&.

.PP
Ordering instructions are accessible from the website of the Radio Technical Commission for Maritime Services: \fIhttp://www.rtcm.org/\fR under "Publications"\&.

.SH "BUGS AND LIMITATIONS"

.PP
RTCM\-104 represents floating\-point quantities as an integer multiple of a fixed scale factor\&. Editing an RTCM\-104 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 RTCM\-104 will be rounded down to the nearest scale unit, and dumping will show slightly different numbers than those you entered\&.

.PP
The decoder logic is sufficiently convoluted to confuse some compiler optimizers, notably in GCC 3\&.x at \-O2, into generating bad code\&.

.SH "SEE ALSO"

.PP
 \fBgpsd\fR(8), \fBgps\fR(1), \fBlibgps\fR(3), \fBlibgpsd\fR(3), \fBgpsprof\fR(1), \fBgpsfake\fR(1), \fBrtcm\-104\fR(5)\&.

.SH "AUTHOR"

.PP
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: \fIhttp://gpsd.berlios.de/\fR\&.