No satellites?

[Paul Grainger]

Has anyone noticed a problem with their nav system or road angel (or similar) the last two afternoons?

My comand has shown '0 satellites' for the last two afternoons (and yet still seems to accurately show the car position on the map screen), also my Inforad (similar to road angel) can't get a satellite lock.

Both systems use seperate antennas. I noticed the problem yesterday afternoon - this morning all was OK. This afternoon - same problem.

Is it just me? Equipment malfunction? Or is something happening with the satellite network?

Paul G

[Brett]

Had the same thing - but as my car has had so many problems recently, I assumed it was something to do with it, not the spinning things above us!

[Maff]

Our ML has had this problem for about 4 months, which I guess means the equipment is faulty!

[RichardM]

I haven't had any problems with my RoadAngel 2.

[Aswall]

No probs with my Roadpilot or TomTom'd Ipaq

[splang]

No probs with my COMMAND
;)

[steve_bcs]

no probs here with comand or b2 or navi plus

[glojo]

My comand has shown '0 satellites' for the last two afternoons (and yet still seems to accurately show the car position on the map screen), also my Inforad (similar to road angel) can't get a satellite lock.

Both systems use seperate antennas. I noticed the problem yesterday afternoon - this morning all was OK. This afternoon - same problem.


It sounds like you have a problem but its strange how both units are affected. The COMAND will use dead reckoning to display your position.

Good luck in solving the mystery,
John

[mark.t]

no probs ...on my B2..or...tomtom

[prprandall51]

Perhaps the US is planning an attack somewhere?

The satellites sometimes get moved around to optimise their use for their original intended purpose - assisting the US military (or, at least, they used to - I don't know if they still do).

During the Gulf war I observed a lack of satellites in the northern hemisphere. Most of the visible satellites are usually south of the UK anyway. Do your receivers have a view of the south? If the antenna was mounted on the dash and you are facing north, the car's roof would shield the antenna from most / all of the visible satellites.

Philip

[glojo]

Perhaps the US is planning an attack somewhere?
Philip

:D :D Hi Philip
I understand what you are saying but at least we are safe here in the South-West as the satellites are happily pinging away.

Don't suppose my old Decca would be of any use in the car ;) ;)

John

[Satch]

GPS is not infalliable and can lose it or give errors for a variety of reasons outside the control of the GPS unit itself. Tend not to see that in the publicity

Orbital error The positions of the satellites obtained from the signal information are really a prediction of where the satellite should be at a given moment, and can differ slightly from the actual position.

Clock errors Not difficult to achieve given that a 10 nanosecond (0.00000001 sec) difference causes a 3-metre error.

Ionospheric and Tropospheric Delay Signals are delayed slightly or masked in their journey to the receiver by traveling through an area of charged particles in the ionosphere.

Multipath errors and Local blocking The GPS signal may bounce off a nearby object and confuse GPS. In a City, a valley or even heavy tree cover one or more of the satellities may not be "seen" by the receiver

Receiver Noise & Induced Noise How well can a given GPS receiver measure the faint signal coming from the satellite? Well, some are better at it than others!

Bad geometries certain spots on the Earth where the arrangement of some of the satellites (from the point of view of the receiver) is confusing: too closely grouped, in a line etc.

This is why on live navigation training exercises the use of a GPS is sometimes forbidden and "traditional" methods have to be used.