C125 GPS drop outs.

[Ady Smith]

Hi all, just wondering if anyone has experienced a problem we are seeing, i have search in this forum but not come up with anything like our issue?

We are running 2 cars in a local saloon car championship, both running C125 dash's with logging, after viewing the logging from both cars i notice one car has something odd happening with the GPS speed and position, it doesn't drop out all together but reads very low for speed and doesn't follow the track for position, this happens multiple times around a lap and at different tracks, at first we thought it may be a problem with the arial so fitted a new one, the problem is still the same.
I've attached a screen shot of the issue, as you can see we are running individual wheel speed censors too
(Wheel speed 78mph / GPS 28.8mph).

Anyone have any idea's as I'm stumped?

[David Ferguson]

Are you using the GPS L-10 receiver or something else?

How much load to you have on the 5V supply? (it's only rated for 250mA)

I have a customer that reported he cleared up his GPS issues with the GPS L-10 by using a separate 5V power supply (basically a 12V USB car adapter he disassembled and wired the 12V in and 5V out).

[Ady Smith]

Hi David
Thanks for the input and ideas.
I can confirm we are using the GPS L10, checking the wiring the feed for it comes from the dash and is the only thing on the 5 volt supply.

Thanks Ady

Are you using the GPS L-10 receiver or something else?

How much load to you have on the 5V supply? (it's only rated for 250mA)

I have a customer that reported he cleared up his GPS issues with the GPS L-10 by using a separate 5V power supply (basically a 12V USB car adapter he disassembled and wired the 12V in and 5V out).

[adrian]

Where do you have the GPS mounted?

[Ady Smith]

Where do you have the GPS mounted?

The Ariel is on the dash, same place as the other car without any issues on that one?

[adrian]

So many things affect how well the GPS works because the signal strength is so low. It could be that it is slightly closer to the 'A' pillar than the other car, or slightly further back so it doesn't see satellites directly above the vehicle. The Dash surface might be slightly different and giving more signal reflections etc etc etc.

The car that's not working properly doesn't have a heated windscreen does it? That will definitely stop it working properly.

The ideal location is on a metal surface at the highest point of the vehicle (the roof) where there is nothing obstructing the view of the sky in any direction.

If it doesn't have a heated windscreen what is most likely happening is it is satellite switching as you change direction and it is losing accuracy. As it is mounted on the Dash it really only sees satellites out the front of the vehicle. As you change direction the satellites it sees change and you get accuracy issues.

[Ady Smith]

Thanks Adrian, we will move the Arial and see if that helps this weekend.

I have had similar issues in other cars in the past with a v-box but as we are using 2 cars the same and one is ok we sort of dismissed it, worth a try though, fingers crossed it sorts it.

Thanks for the input.