[Taxacom] Accuracy of GPS Receivers, was...

Curtis Clark lists at curtisclark.org
Thu May 9 22:45:22 CDT 2013

On 2013-05-09 7:28 PM, Robert Mesibov wrote:
> I've been using Google Earth more and more in recent years, first to check that a GPS reading is for the site I thought it was, second to get an approximate elevation above sea level for the site, and third to 'displace' the GPS reading when required - like when I couldn't get a reading deep in a forested gully, and had to move 50 m to a nearby clear spot to get a reading. In the latter cases, again, I'm finding the Google Earth position is usually well within that 95%/15m circle advised by the GPS manufacturer.

An issue I've noticed when working with the historical imagery is that 
at least the older aerials are sometimes not properly orthogonalized and 
georeferenced: objects can shift by 20m or more between images. I worry 
that this is also the case with the current image (although roads seem 
to align correctly), and it should be a caveat for determining locations 
from Google Earth.

Curtis Clark        http://www.csupomona.edu/~jcclark
Biological Sciences                   +1 909 869 4140
Cal Poly Pomona, Pomona CA 91768

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