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  {block name=title}GPSBabel development:NMEA 0183 sentences (nmea){/block}
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  <div xmlns="http://www.w3.org/1999/xhtml" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">NMEA 0183 sentences (nmea)</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="fmt_nima.html">Prev</a> </td><th width="60%" align="center">Chapter 3. The Formats</th><td width="20%" align="right"> <a accesskey="n" href="fmt_lmx.html">Next</a></td></tr></table><hr /></div><div xmlns="http://www.w3.org/1999/xhtml" class="section"><div class="titlepage"><div><div><h2 class="title" ><a id="fmt_nmea"></a>NMEA 0183 sentences (nmea)</h2></div></div></div><p class="fmtcapshdr">
    This format can...
    </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p class="fmtcapsitem">
          read and write waypoints
        </p></li><li class="listitem"><p class="fmtcapsitem">
          read and write tracks
        </p></li></ul></div><p>This format has the following options: <a class="link" href="fmt_nmea.html#fmt_nmea_o_snlen" title="snlen option">snlen</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_gprmc" title="gprmc option">gprmc</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_gpgga" title="gpgga option">gpgga</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_gpvtg" title="gpvtg option">gpvtg</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_gpgsa" title="gpgsa option">gpgsa</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_date" title="date option">date</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_get_posn" title="get_posn option">get_posn</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_pause" title="pause option">pause</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_append_positioning" title="append_positioning option">append_positioning</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_baud" title="baud option">baud</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_gisteq" title="gisteq option">gisteq</a>, <a class="link" href="fmt_nmea.html#fmt_nmea_o_ignore_fix" title="ignore_fix option">ignore_fix</a> .</p><p> This format is the file representation of the NMEA 
(National Marine Electronics Association) 0183
log and waypoint format for GPS devices.  Some hardware and software
that work with NMEA-0183 formatted data include:
</p><table border="0" summary="Simple list" class="simplelist"><tr><td>
  <a class="ulink" href="http://homepages.tig.com.au/~robk/datalogger.html" target="_top">GPS Data Logger</a>
</td><td>
  <a class="ulink" href="http://www.visualgps.net/VisualGPSce/default.htm" target="_top">VisualGPS</a>
</td><td>
  <a class="ulink" href="http://www.sparkfun.com/" target="_top">SparkFun GPS Datalogger</a>
</td></tr><tr><td>
  <a class="ulink" href="http://www.gpstm.com/eng/features_eng.htm " target="_top">GPS TrackMaker</a>
</td><td>
  <a class="ulink" href="http://www.gpsu.co.uk/" target="_top">GPS Utility</a>
</td><td>
  AMOD 3080 GPS
</td></tr><tr><td>
  <a class="ulink" href="http://www.gpsmaster.nl/ " target="_top">GPSMaster</a>
</td><td>
  <a class="ulink" href="http://www.kolumbus.fi/eino.uikkanen/geoconvgb/index.htm" target="_top">GeoConv</a>
</td><td>
  Wintec WPL-1000 GPS
</td></tr><tr><td>
  <a class="ulink" href="http://www.silcom.com/~rwhately/index.html" target="_top">NMEAlog</a>
</td><td>
  <a class="ulink" href="http://www.commlinx.com.au/GPS_recorder.htm" target="_top">CommLinx GPS recorder</a>
</td><td>
  Sony GPS_CS1
</td></tr></table><p>
This module also supports <a class="link" href="tracking.html" title="Realtime tracking">realtime tracking</a> 
which allows realtime position reports from a GPS, such as one connected 
serially, over Bluetooth, or a USB module emulating a serial port, to be used
with selected output formats.  Just specify an input file that is the device
name such as COM1: for Windows or a device-dependent name like
/dev/cu.usbserial for Mac or /dev/ttyUSB0 for Linux.  (Note that serial 
device names vary on Mac and Linux.)
</p><p>
When used in <a class="link" href="tracking.html" title="Realtime tracking">realtime tracking</a> mode, if
GPSBabel does not sense incoming NMEA sentences arriving from the port, it
will send Sirf "reset to NMEA" commands to the port at a variety of speeds
in an attempt to communicate with an attached GPS.   This lets devices
like the Microsoft GPS or Pharos GPS that are Sirf chips with an integrated
USB/Serial adapter work with this input format.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_snlen"></a><code class="option">snlen</code> option</h3></div></div></div><p>
      Max length of waypoint name to write.
    </p><p>
This option specifies the maximum length to be used for waypoint names in 
the GPWPL sentence.  Longer names will be shortened to no more than this 
length, but all waypoint names will remain unique.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_gprmc"></a><code class="option">gprmc</code> option</h3></div></div></div><p>
      Read/write GPRMC sentences.
    </p><p>
This option tells GPSBabel whether to read (on input) or write (on output) 
GPRMC sentences.  The default is to read or write GPRMC sentences.  To 
disable GPRMC sentences, specify <code class="option">gprmc=0</code>.
</p><p>
GPRMC sentences contain the "recommended mimimum" positional information, 
including date and time, heading, and velocity.  Note that they do not 
include altitude.  For altitude, you will have to include GPGGA sentences.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_gpgga"></a><code class="option">gpgga</code> option</h3></div></div></div><p>
      Read/write GPGGA sentences.
    </p><p>
This option tells GPSBabel whether to read (on input) or write (on output) 
GPGGA sentences.  The default is to read or write GPGGA sentences.  To 
disable GPGGA sentences, specify <code class="option">gpgga=0</code>.
</p><p>
GPGGA sentences contain the location and quality of the GPS position fix.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_gpvtg"></a><code class="option">gpvtg</code> option</h3></div></div></div><p>
      Read/write GPVTG sentences.
    </p><p>
This option tells GPSBabel whether to read (on input) or write (on output) 
GPVTG sentences.  The default is to read or write GPVTG sentences.  To 
disable GPVTG sentences, specify <code class="option">gpvtg=0</code>.
</p><p>
GPVTG sentences contain information about the heading and the speed at the
time of the fix.  They do not contain any location information; for that 
you will need either or both of GPGGA or GPRMC.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_gpgsa"></a><code class="option">gpgsa</code> option</h3></div></div></div><p>
      Read/write GPGSA sentences.
    </p><p>
This option tells GPSBabel whether to read (on input) or write (on output) 
GPGSA sentences.  The default is to read or write GPGSA sentences.  To 
disable GPGSA sentences, specify <code class="option">gpgsa=0</code>.
</p><p>
GPGSA sentences contain information on the quality of the positional fix
and the individual satellites from which it was derived.  However, GPSBabel
neither reads nor writes the individual satellite data.  On input, the 
satellite fields are ignored and on output they are left blank.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_date"></a><code class="option">date</code> option</h3></div></div></div><p>
      Complete date-free tracks with given date (YYYYMMDD)..
    </p><p>
On input, track points with times but no dates will have this date applied.  
</p><p>
This is necessary because some NMEA sentences contain times but no dates.  If
this option is not specified and the date cannot be determined from one or 
more of the available NMEA sentences, the tracks will be discarded.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_get_posn"></a><code class="option">get_posn</code> option</h3></div></div></div><p>
      Return current position as a waypoint.
    </p><p>This options, when specified, returns the current position as a single
waypoint.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_pause"></a><code class="option">pause</code> option</h3></div></div></div><p>
      Decimal seconds to pause between groups of strings.
    </p><p>
This option tells GPSBabel to pause between individual track records when
used on output.  This may be used with appropriate external software or 
hardware to simulate a GPS receiver for testing purposes.  On Unix, for
example, you may use a named pipe to feed the output from GPSBabel to gpsd.
</p><p>
If a value for this option is specified, it is in seconds and it may be
either a whole number of seconds or a fraction (e.g. 0.5 for a 1/2 second
pause between trackpoints.)
</p><p>
If this option is specified without a value, the time between adjacent 
trackpoints will be computed and used for the length of the pause.  That is,
if your trackpoints are 5 seconds apart, GPSBabel will pause 5 seconds 
between trackpoints.
</p><p>
Note that very long tracks may be subject to clock drift, as GPSBabel does 
not take into account the amount of time it may take to write the NMEA 
sentences.  Also, there is no guarantee that it will pause for exactly the
specified number of seconds between samples; different operating systems 
will allow greater or lesser precision for timers, so actual precision may
be as much as plus or minus 100 milliseconds.
</p><p>
If you are using this option with compressed or simplified tracks from 
your handheld GPS receiver, you might find the 
<a class="link" href="filter_interpolate.html" title="Interpolate between trackpoints (interpolate)">interpolate</a> filter useful.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_append_positioning"></a><code class="option">append_positioning</code> option</h3></div></div></div><p>
      Append realtime positioning data to the output file instead of truncating.
    </p><p>
	When writing NMEA realtime positioning data, append to the 
	output file instead of truncating it on each successive position
	fix.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_baud"></a><code class="option">baud</code> option</h3></div></div></div><p>
      Speed in bits per second of serial port (baud=4800).
    </p><p>
To the "nmea" module, the "baud" option specifies the baud rate of the
serial connection when used with the real-time tracking option.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_gisteq"></a><code class="option">gisteq</code> option</h3></div></div></div><p>
      Write tracks for Gisteq Phototracker.
    </p><p>
  This option writes the Gisteq format - which has the extension of .GPS - 
  to allow third-party GPS hardware with the Gisteq PhotoTrackr software.  
</p><p>
  The Gisteq PhotoTrackr is a GPS data logger hardware and software package
  that allows one to easily record the locations of where the user has taken
  photos.  The PhotoTrackr software works by comparing EXIF timestamps in
  digital photos with the timestamps in the tracking data.  In doing so, the
  software plots the locations of the photos using Google Maps.  The logging
  format used by the Gisteq hardware is very close to NMEA format, but with a
  few small quirks.  
</p><p>
More information can be found at the 
<a class="ulink" href="http://www.gisteq.com/" target="_top">Gisteq</a> site.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="fmt_nmea_o_ignore_fix"></a><code class="option">ignore_fix</code> option</h3></div></div></div><p>
      Accept position fixes in gpgga marked invalid.
    </p></div></div><div xmlns="http://www.w3.org/1999/xhtml" class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="fmt_nima.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="The_Formats.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="fmt_lmx.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">NIMA/GNIS Geographic Names File (nima) </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Nokia Landmark Exchange (lmx)</td></tr></table></div>
  
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