Hello Markus<div>Thank you for your answer. Just a few more questions :)</div><div><br><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">For orthorectification, you should use a recent version of GRASS<br>
(6.4.2) and not 6.4.0 because the orthorectification procedure has<br>
been recently overhauled and is creating artefacts in earlier versions<br>
of GRASS, particularly for mountainous terrain.<br>
<br></blockquote><div>Thanks</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
There is no preprocessing required before orthorectification, apart<br>
from the organisation of the imagery. The imagery to be orthorectified<br>
should be in a xy location. A separate location with the target CRS<br>
must exist and should hold reference imagery if you do not have Ground<br>
Control Points.<br>
<br></blockquote><div>1- My VHR image has already coordinates. Is this a problem?</div><div>2- Shall I apply Geometric Correction procedure before Orthorectification?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
There will soon (within the next weeks I hope) be an article available<br>
in Computer and Geosciences explaining the orthorectification<br>
procedure in GRASS, entitled "Robust rectification of aerial<br>
photographs in an Open Source environment".<br>
<br></blockquote><div>Is it possible tyo have acces to the draft version?</div><div><br></div><div>Thank you</div><div>Kat</div><div> </div></div></div>