gpsd and AGPS
alexey at feldgendler.ru
Fri Sep 28 17:14:05 CEST 2007
On Fri, 28 Sep 2007 16:39:43 +0200, Ken Yale <kyale at broadcom.com> wrote:
> Sure, the cell operators won't gladly share this data with anybody, but
> there's still something that could be done: the phone could learn the
> CellID <-> area association and use it later (if we are registered at
> some cell we've already been at, we can't be miles away from where we
> were last time at this cell).
> [Ken] Exactly! This would be a good feature for an Open SUPL server.
> The Broadcom SUPL server has this feature also.
Wow, I didn't think about that! I was thinking about accumulating the
learned CellID <-> area data in the phone, but storing it on an open
server would take it one step further, so that the users can benefit from
each other's contributions.
> [Ken[ Your second point: presumed proximity based on most recent
> location is hard-coded into the GTA01 GPS already. However, the GPS
> must derate the accuracy of the position as a function of time. Most
> GPS receivers have this feature already. One problem is when you've
> flown across an ocean, and a 1-or-2 day old (or even 8 hour old) position
> would actually be a negative assistance.
To avoid this, my Garmin does the following: if you turn it on after not
having used it for quite some time AND satellite reception is difficult at
the moment (happens when I turn it on before driving out of the garage),
it asks you: "Have you moved hundreds of miles/km since the last time?"
> [Ken] This could be a feature to be added to the GLLIN by FIC: detect
> this large position change. Some ideas:
> - "flight mode" - tap the city (or airport code) your flying to.
Typing should be optional, of course. So if you just enable flight mode
without typing the destination, it should invalidate the recent location
Change of the cell network ID (not the cell ID), i.e. roaming, is also an
indication that we have probably travelled far. However, this one should
be used with care because some networks in urban areas have poor coverage
so that the phone enters roaming now and then and connects to some other
local cell network.
Alexey Feldgendler <alexey at feldgendler.ru>
[ICQ: 115226275] http://feldgendler.livejournal.com
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