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<div class="moz-cite-prefix">On 2014-12-29 17:33, André Pirard wrote
:<br>
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<blockquote cite="mid:54A18262.8050006@gmail.com" type="cite"> I
created:<br>
<b>SPW(allon) 2012 aerial imagery</b><b><br>
</b><b>SPW(allon) 2009 aerial imagery</b><b></b><br>
</blockquote>
I forgot to add that these photographs may have a perspective
effect.<br>
For example, a wall of a house may be visible so that the roof is
offset.<br>
In one place I checked thoroughly, 2012 2-floor (1) houses are
slanted 1.5 m in one direction and 2009 is slanted the same in the
opposite direction. That means that the exact position of the house
is the bottom of the wall at ground level and that the roofs are
offset by that value. Of course, the wall and offset are visible
only at the end of a row and the offset must be evaluated all along.<br>
All in all, precise tagging is tricky.<br>
Digitalized maps are corrected, so that a gentle way to use them is
to evaluate the offset of the photo and to continue mapping with
that photo.<br>
<br>
Cheers
<br>
<br>
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<td>André.</td>
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<br>
(1) Belgian, not American floors <span class="moz-smiley-s3"></span>
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