Printable View
I have a Garmin Etrex and it works great most of the time for finding brushpiles marked in the lake. But there are a few that always give problems and even change distances while sitting close by. The arrow and distance changes . Could this be caused by a magnetic disturbance in the ground under the water ? It is the same locations everytime. There is a mountain next to the lake but don't think it blocks the signals .:confused:
Sounds like you are losing sattelite coverage.
When you experience the problem...go to your screen that shows how many sattelites your unit is locked on.
When you are sitting still, the GPS will still be trying to show you your direction of travel. The arrow might change without reason (on your part), but from the GPS's point of view it is correct. You actually need to be moving a little to show good direction of travel.
There is also the attribute of gps resolution distance. If the resolution is larger than the smallest unit possible, sometimes as small as 1 m, then you might be close to the middle of a resolution scale and a slight movement of the gps would move you to the next resolution unit. A small movement back could move you back the other way, to the next resolution unit. The difference between these two units could very easily be larger than the small distance you moved while sitting still.
Gravity and water would have nothing to do with it. Loss of coverage could degrade accuracy. I don't know if a low angle reflected GPS signal off the lake could cause accuracy problems.
I agree with JCmMS and Krazy, I think its just the satellites updating....I have one exactly like it, but never noticed it, but again I don't pay much attention to it once I cut the boat off.