Let's see if I understood correctly the concepts involved here, as I am still a
little bit confused...
- TTFF is when no almanac data is available. Unlike what's specified in
http://wiki.openmoko.org/wiki/Neo_FreeRunner , is not 40 seconds but 12 minutes
(no small difference).
- TTFF shouldn't happen almost never, given that mobile phone is always -but
it's first boot *ever*- in normal state as defined here :
http://en.wikipedia.org/wiki/Time_to_first_fix . Unless we have moved in a
100km radius without gps enabled, mobile phone does not have the correct time,
we are in a car / train, and (dunnow if that's an AND or OR) no previous
almanac available, fixes should be a lot quicker. As in, how much?
- AGPS should make ¿everything? ¿TTFF only? by downloading a small data
package.
My questions, then:
- AGPS can be served by the gsm network without data transfer costs? I mean:
does it *need* to download it from the internet (with its GPRS associated
connection and outrageous prices here in Spain), or is it transferred for free
from the GSM operator? I understand this piece of information to be common to
every GPS phone, not just openmoko...?
- In normal conditions a fix is quite quick (as in 2 or 3 seconds) and not too
"expensive" in terms of battery or processing. Is that true?
- If I get in a car fixes get slower unless I have gps constantly on (which
should eat the battery fast).
- Should I travel without network coverage (as in: by tube), when arrived at
destiny fix will be slower. How much slower? Does AGPS help here?
- Is it possible to get some triangulation info from the GSM towers the phone
is connected to? Possible as in "here's how on the openmoko", not as in
"theoretically" ;), which I know that it is -my symbian phone does it, I
remember some profile software which used that.
BTW all of the questions are because I am starting research for my final
university project to do something similar to the "Locate" [1] application for
Android, or the "context engine" from intel [2] , and I would sincerely love to
do it on openmoko. For it to be useful , we would need to get position
information "cheaply" -both in processing, time and battery-, as otherwise we
couldn't be aware enough of the context of the mobile phone to act in
consequence. Phone waiting 12 minutes and using 15% of the battery to realize
we have entered a library and putting it into silence mode doesn't sound so
useful for us ;).
[1]: http://www.techcrunch.com/2008/05/09/sneak-peak-at-android-apps-out-of-mit/
[2]: http://blogs.intel.com/research/2008/03/kevin_kahn_on_redefining_mobil.php
or http://blogs.intel.com/research/2008/04/last_week_the_intel_developer.php
--- El lun, 23/6/08, Francesco Cat <[EMAIL PROTECTED]> escribió:
De: Francesco Cat <[EMAIL PROTECTED]>
Asunto: Re: GPS
Para: "List for Openmoko community discussion" <[email protected]>
Fecha: lunes, 23 junio, 2008 7:31
Ok I really missed what I wanted to say: One of my friends told me
some phones have positioning sistems that are quite unaccurate: they
should be based on cells but have no GPS. He also told me it was "AGPS
that uses only GSM to get information about position". Next time I
will document better instead of just listen to friends :P
Sorry for the big mistake
2008/6/23 Marcus Bauer <[EMAIL PROTECTED]>:
> On Mon, 2008-06-23 at 10:25 +0200, Federico Lorenzi wrote:
>> This seems to be really misunderstood. The GPS is the Freerunner can
>> get a fix with no help whatsoever, it'll just take longer. This is
>> where the AGPS can come in. Download some data off an assistance
>> server, and suddenly your time to fix is much less. There have been
>> posts to this mailing list about it.
>
> My experience with the Freerunner is ~12 minutes TTFF (time to first
> fix) without use of agps and ~4-8 minutes TTFF with agps from
> agps.u-blox.com using the software from openmoko.
>
> The Neo1973 (GTA01) had a TTFF without agps assistance of ~2 min.
>
> However, the freerunner shows correct altitude above geoid whereas the
> Neo1973 shows only height above WGS-84 ellipsoid. Depending on your
> location the difference between WGS-84 and geoid introduces an error
> from -102m to +86m towards your real altitude.
>
>
>
>
>
> _______________________________________________
> Openmoko community mailing list
> [email protected]
> http://lists.openmoko.org/mailman/listinfo/community
>
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