Sylvan Ascent Inc. wrote: > >>I would expect that GPS readings would have error offsets in > >>specific directions depending on environment like a nearby > >>building or terrain shape.
> Has anyone actually made a study of this? I would tend to agree > with this, but does anyone really know? One noticable effect is that the receiver's ability to accurately follow curvy roads decreases with poor satellite visibility. The worst case is a bend inside a tunnel. The unit will report that the road continues straight into the tunnel from both directions, sometimes forming a cross rather than a bend. If multiple tracks along a curvy road are very close, than you can conclude it is an open field, and if tracks diverge a lot, you know it's a forest or urban canyon. If you receive signals through the side window of a bus or train, the reported position can be offset a few metres to that side. I guess this is because the signal from the other side had to travel around the edge of the roof, sometimes bouncing against objects on the side of the road. -- Lars Aronsson ([EMAIL PROTECTED]) Aronsson Datateknik - http://aronsson.se _______________________________________________ Geowanking mailing list [email protected] http://lists.burri.to/mailman/listinfo/geowanking
