how it works currently is that his whole field is sprayed/seeded etc by having some people stand on one side of the field and then also on the other and the tractor needs to drive from one person to the other person, needless to say this is very inefficient as the people don't measure correct and the tractor sometimes doesn't really drive straight to them and misses large pieces..
can anyone tell me if this could keep the tractor within about a meter of a designated track?(what distance error can i expect from a GPS ) where can i find a GPS that's accurate to within a meter?
Will the magnetometer be necessary?
I think it is more feasible (in comparison with DGPS approach) to use an IMU (Inertial measurement unit) preferably with an internal GPS implementation. Such devices are commercially available and in general produce reasonably good localization. A list of IMU models can be found at below address:http://damien.douxchamps.net/research/imu/