<html>
  <head>
    <meta content="text/html; charset=ISO-8859-1"
      http-equiv="Content-Type">
  </head>
  <body text="#000000" bgcolor="#FFFFFF">
    <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
            .8ex;border-left:1px #ccc solid;padding-left:1ex">
            <div link="blue" vlink="purple" lang="EN-US">
              <table align="center">
                <tbody>
                  <tr>
                    <td><br>
                    </td>
                  </tr>
                </tbody>
              </table>
              <div>
                <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>
              </div>
              <table dir="ltr">
                <tbody>
                  <tr>
                    <td><br>
                    </td>
                  </tr>
                </tbody>
              </table>
              ________________________________________<br>
              This message (including any attachments) issued by RAFAEL-
              ADVANCED DEFENSE SYSTEMS LTD. (hereinafter "RAFAEL")
              contains confidential information intended for a specific
              individual and purpose, may constitute information that is
              privileged or confidential or otherwise protected from
              disclosure. If you are not the intended recipient, you
              should contact us immediately and thereafter delete this
              message from your system. You are hereby notified that any
              disclosure, copying, dissemination, distribution or
              forwarding of this message, or the taking of any action
              based on it, is strictly prohibited. If you have received
              this e-mail in error, please notify us immediately by
              e-mail mailto:<a moz-do-not-send="true"
                href="mailto:lawraf@rafael.co.il" target="_blank">lawraf@rafael.co.il</a>
              and completely delete or destroy any and all electronic or
              other copies of the original message and any attachments
              thereof.
            </div>
            <br>
            _______________________________________________<br>
            gdal-dev mailing list<br>
            <a moz-do-not-send="true"
              href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><br>
            <a moz-do-not-send="true"
              href="http://lists.osgeo.org/mailman/listinfo/gdal-dev"
              target="_blank">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a><br>
          </blockquote>
        </div>
        <br>
        <br clear="all">
        <div><br>
        </div>
        -- <br>
---------------------------------------+--------------------------------------<br>
        I set the clouds in motion - turn up   | Frank Warmerdam, <a
          moz-do-not-send="true" href="mailto:warmerdam@pobox.com"
          target="_blank">warmerdam@pobox.com</a><br>
        light and sound - activate the windows | <a
          moz-do-not-send="true" href="http://pobox.com/%7Ewarmerdam"
          target="_blank">http://pobox.com/~warmerdam</a><br>
        and watch the world go round - Rush    | Geospatial Software
        Developer<br>
      </div>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <br>
      <pre wrap="">_______________________________________________
gdal-dev mailing list
<a class="moz-txt-link-abbreviated" href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a>
<a class="moz-txt-link-freetext" href="http://lists.osgeo.org/mailman/listinfo/gdal-dev">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a></pre>
    </blockquote>
    <br>
  </body>
</html>