[maemo-developers] AGPS performance

[From: Simon Pickering]

Hi all,

Just a quick question. Diablo has seen the introduction of working AGPS
(yay!), but I've been wondering if we'd gain better performance by having a
more accurate way of telling the SUPL server (which sends us the data we
need about satellite positions, etc.) where we are?

The tail-end of https://bugs.maemo.org/show_bug.cgi?id=2878 has some
comments on this (and Quim told me to make an enhancement bug, but I'm not
yet sure whether this will enhance anything, hence the email). Does it make
any difference if we have something more accurate than the ~300km radius
Marko is talking about?

If it does make some (minor?) difference then it would be worth having an
API to be able to access the SUPL service so that it could be integrated
with maemo-mapper (which has much higher magnification on the map and
therefore would give more precise locations than the ~50mile square pixels
in agps-ui) and/or integrate it with GeoClue to use other backends to
provide an initial location.

I don't know enough about this stuff. Does anyone know if:
a) the SUPL server calculates the ephemeris/etc. data for the exact position
that is sent to it, or does it only calculate for some specific sized grid,
then returns the nearest set of data? 
b) The area over which the ephemerides/etc. are actually valid (is it really
a ~300km radius or is this just "good enough" for most cases)?

Thanks,


Simon