Thread: Theory about why GPS performs poorly
View Single Post
ag2 is offline ag2
2008-02-07 , 09:13
Posts: 164 | Thanked: 132 times | Joined on Dec 2007
#84
Originally Posted by lardman View Post
Has anyone (who can get their gps to work more easily than me) captured the NMEA sentences for the Almanac data? If so, could they post them and nvd_data for people to take a look at please?

The ephemeris data aren't exported in the NMEA output afaik, so we'll have to work out the format ourselves. The other problem is that the GPS chip may need to be told to output and intput the almanac/ephemeris data (perhaps why there are lots of 0x0s in nvd_data).
Almanac ($GPALM) is not exported via NMEA by gpsdriver

strings gpsdriver | grep "^\\$"
$GPGGA,%s,%s,%s,%c,%s,%s,%s,%s,,
$GPGLL,%s,%s,%s,%c,%c
$GPGSA,%c,%c,
$GPGST,%s,%s,%s,%s,%s,%s,%s,%s
$GPGSV,%u,%u,%02u
$GPRMC,%s,%c,%s,%s,%s,%s,%s,%s,%s,%c
$GPVTG,%s,T,%s,M,%s,N,%s,K,%c
$PNOKU,%s,%s,%s,%s,%s,%s

Again, I believe that almanac data is not used by the chip at all. This is the only explanation for 3 minute cold starts I can think of.

The problem with GPS5300 is that it was designed to be a cell phone chip, to be used primarily with A-GPS. Without A-GPS the chip more or less stinks.
__________________
See my collection of maemo apps: http://nitapps.com