<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 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 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal">Hi<u></u><u></u></p>
<p class="MsoNormal">I have a question about the RPC transform implemented in gdal_rpc.cpp.<u></u><u></u></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.<u></u><u></u></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?<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks<u></u><u></u></p>
<p class="MsoNormal">Yehiyam<u></u><u></u></p>
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