[FOSS-GPS] AGPS for newbies?

[Timo Jyrinki]

2009/1/19 Lauri Hahne <lauri.hahne at gmail.com>:
> I think those coordinates are only used to guide the receiver to find
> the appropriate satellites. I think the server always returns the full
> almanac and ephemeride.

In three kilobytes? The coordinates are sent to the server so that the
server chooses a valid information to be sent back for the location
given. I'm using the agps-onlinec program from
http://svn.openmoko.org/developers/matt_hsu/agps-online/, which
requires the approximate coordinates.

> AGPS allows phones to send the cell-id to the agps server which might
> have a database of base station locations. Base stations don't
> broadcast their location but the server might know it.

I think there are cell-id databases available which some programs use,
that have user-filled information about "this cell-id is in Kamppi,
Helsinki". I wondered about such databases and if some of those also
have some coordinate information or only names for places.

2009/1/19 Michael Tandy <m.j.tandy at warwick.ac.uk>:
> Why not save the receiver's location when it was turned off, and use
> that information when it's turned back on?

Because it's not implemented yet :) But right, I might be asking this
for no good reason since all GPS devices should eventually be used in
the way that the state is saved before poweroff. I was just wondering
that on GSM + GPS devices you always know the cell id even without
turning GPS on, and if you're using AGPS to get faster fixes it might
minimize the data transfer needed to know the approximate coordinates
one is in already beforehand.

-Timo