Raw Data Commands 215
Raw Data Commands
$PASHQ,SAL,[c1]
This command queries for satellite almanac data. c1 is the optional port designator
for the response. If a port is not specified, the receiver sends the response to the
current port.
$PASHR,SAL
This message is not output until the DG16 has completed downloading the current
GPS almanac file. The receiver begins downloading the almanac file automatically
almanac file can be obtained directly from the satellites, which happens
automatically and takes about twelve minutes, or, with the aid of software, a current
almanac file from another receiver can be manually downloaded into the DG16. A
separate almanac message is output for each satellite being tracked. The SAL
message contains information on satellite health, the almanac week number, and
a variety of orbital measurements. The response is output in the format:
$PASHR,SAL,<Satellite almanac data string + checksum>
Table 7.18 outlines the data string format.
Table 7.18. $PASHR,SAL Data String
Field Bytes Content
short prn 2 Satellite PRN number -1
short health 2 Satellite health
float e 4 Eccentricity
long toa 4 Reference time for orbit (sec)
float i0 4 Inclination angle (semicircles)
float omegadot 4 Rate of right ascension (semicircles/sec)
double roota 8 Square root of semi-major axis (meters 1/2)
double omega0 8 Longitude of ascending node (semicircles)
double omega 8 Argument of perigee (semicircles)
double m0 8 Mean anomaly at reference time (semicircles)
float af0 4 Clock correction (sec)
float af1 4 Clock correction (sec/sec)
short wna 2 Almanac week number
short wn 2 Week number
long tow 4 Seconds of GPS week
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