On a number of ocassions, on a number of threads, a number of people have reported errors with GPS. As yet nobody has explained how this could happen. Can you?
This is my position. There are errors in the GPS system but they are not systemmatic. There is
no error that can affect more than one satellite in the same way.
Now move to your receiver. It needs 4 satellites to create a 3d fix. Three for the geometry and one to correct the time error in the receiver.
Clearly you have a problem if you are below this number but my £100 GPS shows this failure.
At this number maybe you are sensitive to an error in any one satellite. However typically you are running more. Up to 12. Unless the reciever is so stupid that it tracks 8 satellites and then simply discards the surplus ones, you must have some averaging process going on. How in this scenario can it
possibly be fooled into reporting an incorrect position?
Now I have omitted to mention one problem situation - jamming/interference. I assume for this that no normal interference/jamming will fool the receiver. It will simply lose the signal and thus report insufficent satellites. Not an error - just a can't work situation.
So there we are. Anybody going to take me on on this one?