thoughts on A-GPS offline
daniel at openmoko.org
Sun Mar 1 20:31:16 CET 2009
On Tue, 17 Feb 2009 13:07:54 +0100
Rikard Nilsson <janrikard at gmail.com> wrote:
> would it be possible to get the satelite information that we get from
> u-blox from somewhere else?
> somewhere that dont require user account?
there are three possibilities that I see here:
1) mirror the data from u-blox somewhere
2) See whether we can use the information
from http://www.ngs.noaa.gov/orbits/ to provide our own aiding data
3) Set up a stationary GPS receiver and use aiding data from there
1: Someone said that u-blox explicitly allows redistribution of their
AGPS online data. This would be great since we already have all the
data in UBX format.
2: Calculating almanac/ephemeris data from the files present in
ftp://igs.ensg.ign.fr/pub/igs/products/ should be possible, but is far
less straight forward than variant 1.
Additionally to studying ICD-GPS-200
(http://www.navcen.uscg.gov/PUBS/gps/icd200/icd200cw1234.pdf) one would
need to parse the sp3c format:
3: This would be a pretty simple and good way of setting up our own
aiding server if 1 doesn't work out. The problem with this approach is
that we only get ephemeris for SVs in our view so if I set up one
station in Germany it wont help at all in the US. This could be worked
around by having many such stations all over the world.
Now that hot-/warmstart with ephemeris playback works with the framework
we should try to get an open server with aiding data available ASAP.
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