So in summary, the data you want probably doesn't exist. We don't know nearly as much about the detail of surface of our planet as we might think we do...

...and your GPS receiver could capture the data you want, but only by tediously sitting for extended times at the locations of interest to get a decent average.


Edited by andy (08/01/2017 11:14)
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Remind me to change my signature to something more interesting someday