Empty pixels around the image when doing a Terrain-Correction with external DTM

Hi,

I’m terrain-correcting a High-resolution Stripmap TerraSAR-X image using the LiDAR DTM (1 resolution Digital Terrain Model) available for that area. The problem I’m observing is that there are many pixels around the terrain-corrected image that contain NaN values (and I need to eventually make a subset to get the information needed only).

This same problem doesn’t appear when I terrain-correct the same image using the auto-download option with the SRTM DEM 1-arc-second (30m resolution).

Below is the portion of the graph I’m using to do the terrain-correction, and the terrain-corrected image with the extra space. Is the difference in the resolution between the SAR image and the LiDAR DTM responsible for the extra-empty-space?

  <node id="Terrain-Correction">
    <operator>Terrain-Correction</operator>
    <sources>
      <sourceProduct refid="Calibration"/>
    </sources>
    <parameters class="com.bc.ceres.binding.dom.XppDomElement">
      <sourceBands>Sigma0_HH</sourceBands>
      <demName>External DEM</demName>
      <externalDEMFile>C:\Data\LiDAR\dtm-wgs84.tif</externalDEMFile>
      <externalDEMNoDataValue>-9.999</externalDEMNoDataValue>
      <externalDEMApplyEGM>true</externalDEMApplyEGM>
      <demResamplingMethod>BILINEAR_INTERPOLATION</demResamplingMethod>
      <imgResamplingMethod>BILINEAR_INTERPOLATION</imgResamplingMethod>
      <pixelSpacingInMeter>2.2</pixelSpacingInMeter>
      <pixelSpacingInDegree>1.9762936250629475E-5</pixelSpacingInDegree>
      <mapProjection>GEOGCS[&quot;WGS84(DD)&quot;, &#xd;
  DATUM[&quot;WGS84&quot;, &#xd;
    SPHEROID[&quot;WGS84&quot;, 6378137.0, 298.257223563]], &#xd;
  PRIMEM[&quot;Greenwich&quot;, 0.0], &#xd;
  UNIT[&quot;degree&quot;, 0.017453292519943295], &#xd;
  AXIS[&quot;Geodetic longitude&quot;, EAST], &#xd;
  AXIS[&quot;Geodetic latitude&quot;, NORTH]]</mapProjection>
      <alignToStandardGrid>false</alignToStandardGrid>
      <standardGridOriginX>0.0</standardGridOriginX>
      <standardGridOriginY>0.0</standardGridOriginY>
      <nodataValueAtSea>true</nodataValueAtSea>
      <saveDEM>false</saveDEM>
      <saveLatLon>false</saveLatLon>
      <saveIncidenceAngleFromEllipsoid>false</saveIncidenceAngleFromEllipsoid>
      <saveLocalIncidenceAngle>false</saveLocalIncidenceAngle>
      <saveProjectedLocalIncidenceAngle>false</saveProjectedLocalIncidenceAngle>
      <saveSelectedSourceBand>true</saveSelectedSourceBand>
      <outputComplex>false</outputComplex>
      <applyRadiometricNormalization>false</applyRadiometricNormalization>
      <saveSigmaNought>false</saveSigmaNought>
      <saveGammaNought>false</saveGammaNought>
      <saveBetaNought>false</saveBetaNought>
      <incidenceAngleForSigma0>Use projected local incidence angle from DEM</incidenceAngleForSigma0>
      <incidenceAngleForGamma0>Use projected local incidence angle from DEM</incidenceAngleForGamma0>
      <auxFile>Latest Auxiliary File</auxFile>
      <externalAuxFile/>
    </parameters>
  </node>