GPS Receiver "Orientation"

phuz · 07-17-2008, 06:17 AM

I notice something with my new USB GPS receiver. When tracking in IG4, it appears as if I am constantly facing a different direction, but still going down the same street. Also, every now and then it looks as if I am going down the street sideways. I doubt this is the case, but I was wondering if this has anything to do with the fact that I have the receiver mounted backwards in my front dash, so that the cord can be tucked neatly away. I also have a 15' USB cable from the PC going to a non-powered hub, and the 6' USB GPS cable is plugged into that hub, so the GPS is a good distance away from the power. Could this also be causing some of these issues?

2k1Toaster · 07-17-2008, 06:35 AM

Not unless IG4 is doing something strange. GPS has no idea what direction you are facing, nor does it care. It knows position and that is it. Not speed, not direction, but position.

So all GPS programs I know of measure 2 points with a known time. Line from first point to second point is direction. Distance between them divided by the time is the speed and so on.

So if you happened to get a position location "behind" you, IG4 will think that is the direction you are going. But I am sure they use many more than 2 points and an average so you dont bounce around.

So basically in conclusion, the only thing causing this is a lack of signal. If it is covered by metal slightly so 1 of the sats comes in by reflection, that could be enough of a time difference to cause a shadow behind you. Put the receiver outside your car open to the sky. Drive for a while. If you dont get turned around anywhere, you know why.

phuz · 07-17-2008, 06:54 AM

No, it's sitting right in the front dash....wide open. I guess I will have to wait until I get my powered USB hub, and see if that changes anything...otherwise this receiver is going back!

2k1Toaster · 07-17-2008, 07:25 AM

Glass could have a metallic film about it. Could be your windshield isnt sloped enough and its only getting half the signals because the rest are blocked rom your metal car...

Just stick the thing outside the car in the open (on the roof or something) and test. If you are going to return it, you have to unroute it anyways, so not like anything is lost, you could just save money.