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

[tichi]

Originally Posted by 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.

thnx, I do mention it in the very end of the post, but it does not work for me...

[tichi]

So then, an possible explanation of
the phone being stuck sometimes is the following:

because it tries to update GPS sat positions
using AGPS from an invalid server
(which does not know/not allowed to share the data about Bell towers),
and somehow it never arrives to the idea to search for the new satellites?

[tichi]

Originally Posted by ckl_88

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

updated .. did a few more tests like this:

so I disabled it, soft-reset,, tested GPS, then enabled it, soft reset again, tested GPS, etc...

a few times I got a lock within a minute.. once did not get a lock within few minutes, then GPS froze..

so there seems to be NO difference, and it looks like
the phone DOES NOT download ephemeris data from that Belgium server
and it DOES NOT help to Bell users

????

[ckl_88]

I guess you are lucky in that mine is stuck most of the time! HA HA.

My AGPS settings are basically the same except my GPSMode is at 4.

Anyway, here are my random observations (please bear with me).

1. If I get a fix of about 4 sats, if I turn the GPS unit off (ie. quit all gps apps and put the phone to sleep), after about an hour or two, the time to fix is the same as my cold fix times (1-1.5 minutes).

2. I've been using the latest sprint radio (3.42.xx) for a few weeks now. Ever since then, when I go into Google Maps and select Use GPS, the blue dot puts me in the middle of nowhere. When I say nowhere, I mean a map doesn't even display. all I get is a blue dot on a background of row upon row of magnifying glasses with a minus sign in them. No amount of zooming in or out helps. Then yesterday, I downgraded to the Alltel radio (3.37.10) and tried google maps again. Upon selecting the Use GPS, 10 seconds later, it put me about 4 km from my actual position. Just tried it now and it put me about 1 km from actual position here at work. So my phone, with this radio, is finding my general location. That said, time to fix is still about 1-1.5 minutes.

3. In QPST, I've tried adding the PDE server that was recently discovered from the Telus ROM. On average, my cold fix times haven't changed much. I don't know if Bell users are authorized to use that PDE server or not, but it's not making any difference for me.

Personally, I think the GPS units on Bell phones are falling back to Autonomous mode because the AGPS and PDE servers (from other providers) are not providing the correct information (if at all).

I think that if we can figure out the Bell PDE and AGPS servers then we can expect some pretty quick cold fix times.

BTW, when I did some searching for bell PDE servers, I came across a blackberry forum with Bell users with blackberrys with the same exact problem.... long cold fix times.

[tichi]

Thank you for the info, ckl_88!

> My AGPS settings are basically the same except my GPSMode is at 4.

afaik, it not only tries tro GET the ephemeris data, but also to send them to server, and to fine-tune?
which should make no dofference if the server is not replying anyway...


> 1. If I get a fix of about 4 sats, if I turn the GPS unit off (ie. quit all gps > apps and put the phone to sleep), after about an hour or two, the time
> to fix is the same as my cold fix times (1-1.5 minutes).

an hour is enough to lose a satellite.. makes sense? (their period is
about 12 hours?)

> 2. I've been using the latest sprint radio (3.42.xx) for a few weeks now. > Ever since then, when I go into Google Maps and select Use GPS, the
> blue dot puts me in the middle of nowhere. When I say nowhere, I mean > a map doesn't even display.

coordinates 0.0 0.0 ... Atlantic ocean somewhere near Africa?

> Then yesterday, I downgraded to the Alltel radio (3.37.10) and tried
> google maps again. Upon selecting the Use GPS, 10 seconds later, it put > me about 4 km from my actual position. Just tried it now and it put me
> about 1 km from actual position here at work. So my phone, with this
> radio, is finding my general location. That said, time to fix is still about
> 1-1.5 minutes.

might it be a coincidence? what's the relation between Google Maps and Radio? otherwise from your description it seems that AGPS works with this radio (though you just said it should not work with Bell phones)?

> 3. In QPST,

btw, do not you know where to get this QPST?


> Personally, I think the GPS units on Bell phones are falling back to
> Autonomous mode because the AGPS and PDE servers (from other
> providers) are not providing the correct information (if at all).

so far it is compatible with my obsrervations...

> I think that if we can figure out the Bell PDE and AGPS servers then we
> can expect some pretty quick cold fix times.

would be very cool!

[ckl_88]

> Honestly I'm bit confused what's the relation between GPSmode # and
> EnableGPSSmartMode .. are not these setting redundant?

I have no idea.

> an hour is enough to lose a satellite.. makes sense? (their period is
> about 12 hours?)

This is just my observation. I have a feeling it may have something to do with the registry key TimeBetweenFixes which is at 1. Not sure what this key actually does, but my guess is that the value specified (whether in hours or days or whatever) is the expiry time for the downloaded data. In other words, the time elapsed in which the GPS will need to reacquire satellite information.

DISCLAIMER: This is just my guess so I could be way off base.

> coordinates 0.0 0.0 ... Atlantic ocean somewhere near Africa?

If it was somewhere near there, I would expect a map with blue (to indicated water) and if I zoomed out far enough, probably see the coast of Africa. However, no amount of zooming out will give me any indication of where I am. Just magnifying glasses with a minus sign in them no matter what I do.

> might it be a coincidence? what's the relation between Google Maps and > Radio? otherwise from your description it seems that AGPS works with
> this radio (though you just said it should not work with Bell phones)?

Yeah, that one got me confused. As a test, I removed the server IP and port in the SUPL AGPS and soft-reset. So now no AGPS is used right? Then I started google maps, searched for my home address which is about 30km away from where I am (at work), selected Use GPS and guess what happened next? IT FOUND MY APPROX. POSITION!!! 1 km away from my work place! I looked at the blue status message on the top right and it said Seeking GPS Satellites (0).... So I've removed the AGPS server, and yet it still found my approx. location.

> btw, do not you know where to get this QPST?

QPST is a commercial app and considered warez and risk possible banning if I say anything more about it so I'll leave it at that.

> so far it is compatible with my obsrervations...

Personally, if my GPS takes more than a minute to get a fix (cold) then AGPS is not working. It should be in the range of 20-30 seconds which is what my N95 can do when I upgraded it's firmware to support AGPS.

[tichi]

> This is just my observation. I have a feeling it may have something to do > with the registry key TimeBetweenFixes which is at 1. Not sure what this > key actually does, but my guess is that the value specified (whether in
> hours or days or whatever) is the expiry time for the downloaded data. In > other words, the time elapsed in which the GPS will need to reacquire
> satellite information.

looks plausible

>> coordinates 0.0 0.0 ... Atlantic ocean somewhere near Africa?
> If it was somewhere near there, I would expect a map with blue (to
> indicated water) and if I zoomed out far enough, probably see the coast > of Africa. However, no amount of zooming out will give me any indication

> Yeah, that one got me confused. As a test, I removed the server IP and > port in the SUPL AGPS and soft-reset. So now no AGPS is used right?
> Then I started google maps, searched for my home address which is
> about 30km away from where I am (at work), selected Use GPS and
> guess what happened next? IT FOUND MY APPROX. POSITION!!! 1 km
> away from my work place! I looked at the blue status message on the top > right and it said Seeking GPS Satellites (0).... So I've removed the AGPS > server, and yet it still found my approx. location.

curious!
my guess is that GoogleMaps is able to retrieve the STORED "last known" location from the GPS chips or wherever, and then it is trying to
center you around this location...
from your story it looks like with the OLDER radio GoogleMaps retrieves this location correctly (or it is simply stored correctly),
while with the newer radio GoogleMaps and radio could not agree on that...
if Google maps gets some garbage as "last known location" from the new radio, and then tries to center you around it, then it explains those confusing screens you get< does not it?

Maybe I should flash the older radio too..
Have you had the older radio from the Alltel rom (as per Tutorial?)
did you install it over the newer one without problems?

> QPST is a commercial app and considered warez and risk possible banning > if I say anything more about it so I'll leave it at that.

thnx I had no idea what is it, that's why asked.. I'll not bother about it then
until I see that it is really needed

[tichi]

> coordinates 0.0 0.0 ... Atlantic ocean somewhere near Africa?

> If it was somewhere near there, I would expect a map with blue (to
> indicated water) and if I zoomed out far enough, probably see the coast > of Africa. However, no amount of zooming out will give me any indication > of where I am. Just magnifying glasses with a minus sign in them no
> matter what I do.


Hey ckl_88, I just tried to experiment with GoogleMaps
it does put you in the (0.0, 0,0) - Guinea Bay - position even with the new radio
(I have the one 3.42.30 or something)..

in order to see it, you shoud enable internet, so that GoogleMaps can download, and also I switched on Satellite View instead of just MAP..

so it seems that there's no difference betweedn new and old radio
wrt this...

P.S.
if it is not too difficult, will you please try a test of Google Maps with the old radio,
in your spare time -
right after SOFT-resetting phone, and resetting google maps (menu, options, reset), and when sats are NOT available,
but internet IS - to osee if it still puts you in the middle of the ocean - (thsi way I think the last known location will be cleared
even wi the older radio).. thnx a lot in advance, I'd like to se if it is indeed useful to downgrade the radio!

[flatspin]

You're right, of course. I was thinking of the WAAS satellites.

Originally Posted by 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/~pogge/Ast162/Unit5/gps.html

[tichi]

useful info for those interested:

Almanac and Ephemeris Data as used by GPS receivers
(4 July 199

The satellites broadcast two types of data, Almanac and
Ephemeris. Almanac data is course orbital parameters for all
SVs. Each SV broadcasts Almanac data for ALL SVs. This Almanac
data is not very precise and is considered valid for up to
several months. Ephemeris data by comparison is very precise
orbital and clock correction for each SV and is necessary for
precise positioning. EACH SV broadcasts ONLY its own Ephemeris
data. This data is only considered valid for about 30 minutes.
The Ephemeris data is broadcast by each SV every 30 seconds.

When the GPS is initially turned on after being off for more than
30 minutes, it "looks" for SVs based on where it is based on the
almanac and current time. With this information, appropriate
SVs can be selected for initial search.

When the GPS receiver initially locks onto a SV, the Garmin
display then shows "hollow" signal strength bars. At this time,
the Ephemeris data has yet to be completely collected. Once the
ephemeris data is collected from EACH SV in turn, the associated
signal strength bar will turn "solid" black and then the data
from that SV is considered valid for navigation.

If power is cycled on a GPS unit, and when turned back on, the
Ephemeris data is less than 30 minutes old, lock-on will be very
quick since the GPS does not have to collect new Ephemeris data.
This is called a "warm" start.

If it is later than 30 minutes, this is considered a "cold"
start and all Ephemeris data will have to be recollected.

If the GPS has moved more than a few hundred miles or accurate
time is lost, the Almanac data will be invalid and if you are
far enough off, none of the SVs that the Almanac thinks should
be overhead will be there. In such case, the GPS will have to
"sky search" or be reinitialized so it can download a new Almanac
and start over.

(Note: Yes! We know this is somewhat simplified information.
Yes, we know that the Ephemeris data may not have to be updated
as often as the G-12XL does it to get data to the G-12XL
accuracy.)

Joe Mehaffey
================================================== ==============


http://gpsinformation.net/main/almanac.txt