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<div class="moz-cite-prefix">Hi Frank,<br>
<br>
I only want to note that the default is bilinear interpolation of
the DEM.<br>
<br>
Part of the code: const char *pszDEMInterpolation =
CSLFetchNameValueDef( papszOptions, "RPC_DEMINTERPOLATION",
"bilinear" );<br>
<pre class="moz-signature" cols="72">Best regards,
Dmitriy</pre>
16.01.2013 22:47, Frank Warmerdam пишет:<br>
</div>
<blockquote
cite="mid:CA+YzLBdvVr+XUBMMkEs9Q3r+jEL4B2SXAJS_FFVDnn7Mb0Y2HA@mail.gmail.com"
type="cite">
<div dir="ltr">Yehiyam,
<div><br>
</div>
<div>I do not see why you think the AREA_OR_POINT value ought to
have any influence on how DEM values are interpolated. </div>
<div><br>
</div>
<div style="">Note that a PixelIsPoint GeoTIFF file will already
result in a GDAL GeoTransform that is offset by half a pixel.
The GDAL GeoTransform always treats pixels as areas, and GDAL
interpolators - presumably including the for RPCs - should
treat the pixel value as being at the center of the pixel area
for the purpose of interpolation (regardless of whether that
value is point or area). </div>
<div style=""><br>
</div>
<div style="">On the other hand, I am denying the possibility
that the RPC DEM interpolation is always off by half a pixel.
I haven't actually looked closely at that code lately and the
RPC code is not so very well tested and validated.</div>
<div style=""><br>
</div>
<div style="">Best regards,</div>
<div style="">Frank</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Wed, Jan 16, 2013 at 4:40 AM, Livneh
Yehiyam <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:yehil@rafael.co.il" target="_blank">yehil@rafael.co.il</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
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<p class="MsoNormal">Hi</p>
<p class="MsoNormal">I have a question about the RPC
transform implemented in gdal_rpc.cpp.</p>
<p class="MsoNormal">If a dem file is specified in the
transform options
(RPC_DEM) the file is sampled to retrieve the
elevation of the transformed point.</p>
<p class="MsoNormal">In the case where the dem file is a
DTED file (which defines
AREA_OR_POINT to POINT), shouldn't the pixel/line
values in the dem file be
offset by half a pixel to get the correct height?</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Thanks</p>
<p class="MsoNormal">Yehiyam</p>
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