+ <para>
+ Packed into a one byte field are status flags and the count of
+ satellites used to compute the position fix. Note that this
+ number may be lower than the number of satellites being
+ tracked; the receiver will not use information from satellites
+ with weak signals or which are close enough to the horizon to
+ have significantly degraded position accuracy.
+ </para>
+ <table frame='all'>
+ <title>GPS Flags</title>
+ <tgroup cols='3' colsep='1' rowsep='1'>
+ <colspec align='center' colwidth='*' colname='bits'/>
+ <colspec align='left' colwidth='2*' colname='name'/>
+ <colspec align='left' colwidth='7*' colname='description'/>
+ <thead>
+ <row>
+ <entry align='center'>Bits</entry>
+ <entry align='center'>Name</entry>
+ <entry align='center'>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>0-3</entry>
+ <entry>nsats</entry>
+ <entry>Number of satellites in solution</entry>
+ </row>
+ <row>
+ <entry>4</entry>
+ <entry>valid</entry>
+ <entry>GPS solution is valid</entry>
+ </row>
+ <row>
+ <entry>5</entry>
+ <entry>running</entry>
+ <entry>GPS receiver is operational</entry>
+ </row>
+ <row>
+ <entry>6</entry>
+ <entry>date_valid</entry>
+ <entry>Reported date is valid</entry>
+ </row>
+ <row>
+ <entry>7</entry>
+ <entry>course_valid</entry>
+ <entry>ground speed, course and climb rates are valid</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ <para>
+ Here are all of the valid GPS operational modes. Altus Metrum
+ products will only ever report 'N' (not valid), 'A'
+ (Autonomous) modes or 'E' (Estimated). The remaining modes
+ are either testing modes or require additional data.
+ </para>
+ <table frame='all'>
+ <title>GPS Mode</title>
+ <tgroup cols='3' colsep='1' rowsep='1'>
+ <colspec align='center' colwidth='*' colname='value'/>
+ <colspec align='center' colwidth='3*' colname='name'/>
+ <colspec align='left' colwidth='7*' colname='description'/>
+ <thead>
+ <row>
+ <entry align='center'>Mode</entry>
+ <entry align='center'>Name</entry>
+ <entry align='center'>Decsription</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>N</entry>
+ <entry>Not Valid</entry>
+ <entry>All data are invalid</entry>
+ </row>
+ <row>
+ <entry>A</entry>
+ <entry>Autonomous mode</entry>
+ <entry>Data are derived from satellite data</entry>
+ </row>
+ <row>
+ <entry>D</entry>
+ <entry>Differential Mode</entry>
+ <entry>
+ Data are augmented with differential data from a
+ known ground station. The SkyTraq unit in TeleMetrum
+ does not support this mode
+ </entry>
+ </row>
+ <row>
+ <entry>E</entry>
+ <entry>Estimated</entry>
+ <entry>
+ Data are estimated using dead reckoning from the
+ last known data
+ </entry>
+ </row>
+ <row>
+ <entry>M</entry>
+ <entry>Manual</entry>
+ <entry>Data were entered manually</entry>
+ </row>
+ <row>
+ <entry>S</entry>
+ <entry>Simulated</entry>
+ <entry>GPS receiver testing mode</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>