GPS is stuck with a set of satellites - how to remove them from memory?

[tichi]

I seem to know why SOMETIMES it takes forever
to get a satellite lock with GPS.
(I learn that many users experience this problem, including those on Bell, and including those with NSFSAN's ROM 1.10, like me).

After you get a successful lock, a few satellite numbers (like those 4,2,9,12,22 etc, that you see in GPSViewer) are stored
somewhere on the phone.

Next, when after some time (overnight, let's say), you try to get another lock, the OLD satellites moved, they are not available anymore,
but the phone tries to use them anyway, WITHOUT UPDATING...

(my highly subjective perception after some observations is that if there's is one-two OLD satellites still avaialble, it may be still OK for the phone to find the new ones, but if NONE of the old satellites are available,
the phone is stuck, and may sit forever looking for them..

what helps is a SOFT-RESET (which clears some memory, I suppose) - after that - ther's a A FAST (10ns) LOCK, with NEW SET OF SATELLITES (e.g .13. 15. 3. 7 etc )..

so my question is WHERE those satellite are stored, and how to clean them without doing a soft-reset?

("HTC GPS Tool" that has some "clear-memory" button does not seems to help, maybe because it is for another phone model?)

EXPERTS, PLEAAASE!

[flatspin]

That doesn't make sense. GPS satellites don't move. They are geo-synchronous.

YOU move however. If you move a certain distance, GPS's have to go through a search process again. It's taken 20 minutes before with my Garmin handheld GPS to get a lock after traveling a couple thousand miles.

[taidan]

Your wrong, GPS sats are in MEO (medium earth orbit). They Move and You move. Stop talking out of your @$$.

OP is correct, the chip does recall sats based on recently downloaded stattelite location information or Almanac. Thats why right after you get a lock its easier to get another one right after. But if you move, or they move, it still thinks the sats are their.

That is also why HTC quick GPS data expires after a while.

Now as to how to fix it, I have no IDEA

[mithodge]

The sats are not geo-synchronous. That is why they need to have location data (ephemeris) uploaded every 4 hours.

"Each satellite in the GPS constellation orbits at an altitude of about 20,000 km from the ground, and has an orbital speed of about 14,000 km/hour (the orbital period is roughly 12 hours - contrary to popular belief, GPS satellites are not in geosynchronous or geostationary orbits). The satellite orbits are distributed so that at least 4 satellites are always visible from any point on the Earth at any given instant (with up to 12 visible at one time)." http://www.astronomy.ohio-state.edu/...Unit5/gps.html

[tichi]

Originally Posted by flatspin

That doesn't make sense. GPS satellites don't move. They are geo-synchronous.

YOU move however. If you move a certain distance

they are not geosync, afaik..

and.. for old man Galileo and for old man Einstein it is all the same anyway..

I suppose, for the GPS chip too ..

[tichi]

Originally Posted by taidan

...the chip does recall sats based on recently downloaded stattelite location information or Almanac. Thats why right after you get a lock its easier to get another one right after. But if you move, or they move, it still thinks the sats are their.

Now as to how to fix it, I have no IDEA

thnx a lot! the POSITIONS too... yes of course...
and then from the old positions, it ( either the software or GPS chip itself?) tries to predict the new positions, somehow, I suppose?
based on time difference? (because it cannot account for your movement)..
Also I wonder if some info from the internet / third parties is used here (like that AssistedGPS etc?)

And then, the problem is
- why some ROM`s / some carriers' phones are able to
update the sat positions correctly, and also use new sats if available,
while SOME others (like Bell phones) are stuck with old useless sats/positions,
and never search for the new ones before soft-reset..

hmmmm.. I've also seen around here written
that there's a dedicated GPS area in memory, somewhere in the "radio" section?
but the "radio" must be ROM, is not it?
and this are must bes flashed often while GPS works... or only when it stops working?
or GPS chip has some RAM/ROM itself?

[ckl_88]

Originally Posted by tichi

I seem to know why SOMETIMES it takes forever
to get a satellite lock with GPS.
(I learn that many users experience this problem, including those on Bell, and including those with NSFSAN's ROM 1.10, like me).

After you get a successful lock, a few satellite numbers (like those 4,2,9,12,22 etc, that you see in GPSViewer) are stored
somewhere on the phone.

Next, when after some time (overnight, let's say), you try to get another lock, the OLD satellites moved, they are not available anymore,
but the phone tries to use them anyway, WITHOUT UPDATING...

(my highly subjective perception after some observations is that if there's is one-two OLD satellites still avaialble, it may be still OK for the phone to find the new ones, but if NONE of the old satellites are available,
the phone is stuck, and may sit forever looking for them..

what helps is a SOFT-RESET (which clears some memory, I suppose) - after that - ther's a A FAST (10ns) LOCK, with NEW SET OF SATELLITES (e.g .13. 15. 3. 7 etc )..

so my question is WHERE those satellite are stored, and how to clean them without doing a soft-reset?

("HTC GPS Tool" that has some "clear-memory" button does not seems to help, maybe because it is for another phone model?)

EXPERTS, PLEAAASE!

hmmm... didn't you say in another thread that you were getting 10sec locks (cold fix)?

Anyway, have you tried turning off the EnableGPSSmartMode in the SUPL AGPS registry? here is link to the post I'm looking at:

http://forum.ppcgeeks.com/showpost.p...09&postcount=8

[tichi]

Originally Posted by ckl_88

hmmm... didn't you say in another thread that you were getting 10sec locks (cold fix)?

Anyway, have you tried turning off the EnableGPSSmartMode in the SUPL AGPS registry? here is link to the post I'm looking at:

http://forum.ppcgeeks.com/showpost.p...09&postcount=8

yes, IF NOT STUCK - within TENS of seconds (from 5 seconds up to a minute maybe).. sometimes can go slower, though, even if not stuck..

thank you for the link, I'm reading right now something about AGPS, and
I see that your link is something about AGPS too..

BTW, here are my AGPS settings,

[HKEY_LOCAL_MACHINE\Software\HTC\SUPL AGPS]
"EnableAGPS"=dword:00000001
"EnableGPSSmartMode"=dword:00000001
"GPSMode"=dword:00000002
"NumberFixes"=dword:3b9ac9ff
"QoSAccuracy"=dword:00000032
"QosPerformance"=dword:00000059
"ServerIP"="195.207.101.126"
"ServerPort"=dword:00001e6c
"TimeBetweenFixes"=dword:00000001

_________________________
I wonder if all this is of any help for BEll users, for example, how
a server located somewhere in Belgium can know about Bell.ca cell towers?

also also I wonder if anyone could share their AGPS settings to compare?

[tichi]

Originally Posted by ckl_88

http://forum.ppcgeeks.com/showpost.p...09&postcount=8

cool!, thank a lot again, this post tells many useful things
(I'll allow myself to quote it here too):

Originally Posted by hetaldp

Being we are non Sprint User the Assistance Server will never accept Requiest from Outer Network so we must have to put the GPS into Autonomous Mode (Self Fixing)

I am using this Setting in SULP (Secure User Plane Client With Extended Ephemeris)

[HKEY_LOCAL_MACHINE\Software\HTC\SUPL AGPS]
"GPSMode"=dword:00000001
"EnableGPSSmartMode"=dword:00000000
"EnableAGPS"=dword:00000000

GPSMode = 1 means Autonomous (Self Fix no Assistance Required, Pessimistic Approach, Very Slow but Very Accurate)
GPSMode = 2 means Assisted by Server (Less Optimistic, Somewhat Slow but Medium Accuracy Quality)
GPSMode = 4 means Assisted by Server with Extended Ephemeris (Very Optimistic, But Sometime we loose Accuracy Quality)

EnableAGPS = 1 Means Enabled AGPS and 0 Disables it

EnableGPSSmartMode = 1 Save Downloaded Ephemeris Data and also Send it Assitance Server to Update / Fine Tune Extended Ephemeris Data on Server (Require Internet Connection), 0 Zero Desables this Feature

Ephemeris Data = To get Self Fix the Device must know the Position of Satelite in sky, which is called as Ephemeris Data, This is Combined Database which have there Altitude, Latitude, Longitude so the Phone , GPS Device don't have to wait to get Satellites Position from Frequent Satellite Self Position Broadcast by Air

[AceszHigh]

Didn't read through the whole post...but all you need to do is download nadavi gps tool and theres an option to clear the gps chip of previous locks/locations.