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My GPS seems to be a little off


Waterboss

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Go back and look at the benchmark page. Does it say that the coordinates are "scaled?" If it does, then the position of the benchmark is only known to within a couple hundred feet.

 

If you want to find benchmarks whose position is well known, look for "triangulation markers" and other benchmarks meant for horizontal control. By far the vast majority of benchmarks are there for vertical control, and will be quite a ways off from the published positions.

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You are using the exact same GPSr setup that I am. I've managed to find a dozen benchmarks with it so I can say that it is most likely not your GPSr.

 

I have noticed that many benchmark descriptions have the coordinates off by a significant amount. As Fizzymagic pointed out most coordinates are scaled from a topographic map. If you look at the official NGS datasheet for those benchmarks you will most likely see that the coordinates have an estimated accuracy of +/- 6 seconds. 6 seconds is more than 500ft. So the official coordinates may be off by quite a bit, rely on the location description for actually finding the markers.

 

I'm not lost!

I just don't know where I am.

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