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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'>I guess that’s my point unless you
are testing against a set of imagery which you know is Aerial imagery orthorectified
with a *<b><span style='font-weight:bold'>very</span></b>* fine DEM or an areas
with constant elevation. You can’t make claims that the presentation of
the image is adversely affecting accuracy. <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>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>For instance the DigitalGlobe Quickbird
satellite is rated as 23m CE90 RMSE 14m.<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>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>http://www.digitalglobe.com/index.php/48/Products?product_id=1<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>
<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><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<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
8:08 AM<br>
<b><span style='font-weight:bold'>To:</span></b> PROJ.4 and general Projections
Discussions<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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