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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>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 <st1:country-region w:st="on"><st1:place
w:st="on">Denmark</st1:place></st1:country-region> 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? -Noel Zinn<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
proj-bounces@lists.maptools.org [mailto:proj-bounces@lists.maptools.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Thomas Knudsen<br>
<b><span style='font-weight:bold'>Sent:</span></b> Sunday, November 30, 2008
9:08 AM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">PROJ.4
and general Projections Discussions</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Proj] Google Earth
Accuracy</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>2008/11/30 Ethan Alpert <<a href="mailto:ealpert@digitalglobe.com">ealpert@digitalglobe.com</a>><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
How come no ones questioning the accuracy of the sensors that collected<br>
the imagery in Google Maps? I happen to know that satellite imagery is<br>
not very accurate unless you have decent ground control and a DEM. Even<br>
then it's not that great. It seems pointless to try to determine<br>
accuracy in Google Maps unless you understand where the imagery came<br>
from and how it was produced.<o:p></o:p></span></font></p>
</blockquote>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
<br>
At least where I live (<st1:place w:st="on"><st1:City w:st="on">Copenhagen</st1:City>,
<st1:country-region w:st="on">Denmark</st1:country-region></st1:place>), the
high resolution<br>
layers of Google Maps come from very high precision<br>
photogrametrically derived orthophotos, which should certainly<br>
have an accuracy way better than the "few meters with occational<br>
ten meter blunders" quoted earlier in this thread. <o:p></o:p></span></font></p>
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