[Proj] Google Earth Accuracy
ndzinn at comcast.net
Sun Nov 30 10:48:52 EST 2008
Ethan makes a valid point from my perspective working in a risk adverse
industry (petroleum). Google Earth comes without an audit trail and "should
certainly" is inadequate assurance without that audit trail for anything
more than rough reconnaissance. (Different industries or applications do
have different standards.) Furthermore, imagery changes over time. What
ties well in Denmark or in The Netherlands or in Irwin's studies or at the
mailbox in front of my house today may not tomorrow. How will we know?
From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of Thomas Knudsen
Sent: Sunday, November 30, 2008 9:08 AM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Google Earth Accuracy
2008/11/30 Ethan Alpert <ealpert at digitalglobe.com>
How come no ones questioning the accuracy of the sensors that collected
the imagery in Google Maps? I happen to know that satellite imagery is
not very accurate unless you have decent ground control and a DEM. Even
then it's not that great. It seems pointless to try to determine
accuracy in Google Maps unless you understand where the imagery came
from and how it was produced.
At least where I live (Copenhagen, Denmark), the high resolution
layers of Google Maps come from very high precision
photogrametrically derived orthophotos, which should certainly
have an accuracy way better than the "few meters with occational
ten meter blunders" quoted earlier in this thread.
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