GPS Fix Problem

matt1971 · Posted: Mon Nov 24, 2003 5:02 pm Post subject: GPS Fix Problem

Hi,

Apologies if I have asked this in the wrong forum!!

On Saturday 22nd Nov, in London we were having torential rain (Around 18:00GMT). Whilst out driving with Co-pilot 4, Navman GPS Sleeve - I was getting around 7-8 good satellite fixes however I could not even get a 2d fix.

Later that evening (22:00GMT) I kept getting no GPS signal - as though the sleeve was not connected. Throughout this time I have re-inserted the jacket, reset the Ipaq etc all with the same result. However around 23:00(GMT) it just suddenly worked. On sunday it worked fine although took longer TTFF than normal.

I have the unit for about 1 year and have never had this issue before - I mention the rain as I am not sure whether this affects the GPS signal.

Is there any other logical reason for this?

Thanks

Matt

lbendlin · Posted: Mon Nov 24, 2003 5:48 pm Post subject:

Having 7-8 sats visible doesn't yet help much. They are constantly moving around the earth, and they may end up in constellations that are less than favourable for a 3D or even 2D fix. For example, if they are all in a row, then they are useless. For a 2D fix you need at least 3 Sats, and they must be as far from each other as possible. For a 3D fix you need at least 4 Sats.

Sure the rain may have had some effect, but I'd rather blame it on an unlucky constellation (sic)
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

Dave · Posted: Mon Nov 24, 2003 9:52 pm Post subject:

Unlucky constellation is definately one cause, and also moving, I'm not too sure if you followed much our threads on the older Navman 3000 sleeves (ALK/TravRoute have stopped selling these). The sleeves themselves worked, but TTFF's could be extended, especially if you commenced driving, sometimes up to 45 mins, and this wouldn't surprise me that you experienced these problems.

It is always best to sit and wait to get a fix, sometimes due to ionosphere problems, constellations, and also trees and buildings that may be in the way which will cause signals to rebound and weaken (multi-path errors), this can all degrade the signal you are receiving.

Another reason for receiving 7-8 sats but never getting a 3D fix can also be down to the time on your Pocket PC. If it's out by a few hours, this can cause problems.

matt1971 · Posted: Tue Nov 25, 2003 10:18 am Post subject:

Hi,

Thanks for both of your insights.

Matt

	PocketGPS
	Web