How exactly does GPS bearing work?

skatj

I'm working on a GPS navigation robot and I was wondering exactly how it gets its bearing information. Is it done by calculating vectors based on its current movement, or is it done by some other way?

In other words, say a differentially driven robot was turning on its axis, would the GPS receiver detect this change in angle if it was not moving?

Phil Pilgrim (PhiPi)

A GPS receiver gives position only. It can tell the direction you're moving via successive positions. It cannot tell the direction you're facing under any circumstances. For the latter, a compass module would be necessary.

-Phil

CMcG

Hi Skatj,

Phil is absolutely right. you need to be looking at suplementing the GPS position with an extrernal compass module.

GPS bearing is worked out from successive GPS positions. This works fine if you are walking or driving along with your GPS receiver but be careful, when you are stationary, GPS positions still have a small 'wander' range of a few metres and the displayed bearing value is, as you have probably already seen, apparantly random and of no use. Hence the need to use a compass bearing when for example GPS speed is < 4mph.

Good luck with the robot project.

Carl

achilles03

CMcG said...
Hi Skatj,

Phil is absolutely right. you need to be looking at suplementing the GPS position with an extrernal compass module.

GPS bearing is worked out from successive GPS positions. This works fine if you are walking or driving along with your GPS receiver but be careful, when you are stationary, GPS positions still have a small 'wander' range of a few metres and the displayed bearing value is, as you have probably already seen, apparantly random and of no use. Hence the need to use a compass bearing when for example GPS speed is < 4mph.

Good luck with the robot project.

Carl

I'm not sure that is correct. At least some GPS recievers can estimate velocity based on the doppler shift of the tracked satellites.

Dave