Auto UTM zone in the graph file?

dzatta · June 7, 2019, 8:00am

I don’t see any crs parameter field in the xml file… so I don’t understand how I am supposed to set it. (sorry, I am new to SNAP and projections, so I am a bit confused)

Currently this is my Terrain-Correction node in the xml graph:

  <node id="Terrain-Correction">
    <operator>Terrain-Correction</operator>
    <sources>
      <sourceProduct refid="Calibration"/>
    </sources>
    <parameters class="com.bc.ceres.binding.dom.XppDomElement">
      <sourceBands/>
      <demName>SRTM 1Sec HGT</demName>
      <externalDEMFile/>
      <externalDEMNoDataValue>0.0</externalDEMNoDataValue>
      <externalDEMApplyEGM>true</externalDEMApplyEGM>
      <demResamplingMethod>BILINEAR_INTERPOLATION</demResamplingMethod>
      <imgResamplingMethod>BILINEAR_INTERPOLATION</imgResamplingMethod>
      <pixelSpacingInMeter>10.0</pixelSpacingInMeter>
      <pixelSpacingInDegree>8.983152841195215E-5</pixelSpacingInDegree>
      <mapProjection>PROJCS[&quot;WGS 84 / Auto UTM&quot;,
  GEOGCS[&quot;WGS84(DD)&quot;,
    DATUM[&quot;WGS84&quot;,
      SPHEROID[&quot;WGS84&quot;, 6378137.0, 298.257223563]],
    PRIMEM[&quot;Greenwich&quot;, 0.0],
    UNIT[&quot;degree&quot;, 0.017453292519943295],
    AXIS[&quot;Geodetic longitude&quot;, EAST],
    AXIS[&quot;Geodetic latitude&quot;, NORTH]],
  PROJECTION[&quot;Transverse_Mercator&quot;],
  PARAMETER[&quot;central_meridian&quot;, 3.0],
  PARAMETER[&quot;latitude_of_origin&quot;, 0.0],
  PARAMETER[&quot;scale_factor&quot;, 0.9996],
  PARAMETER[&quot;false_easting&quot;, 500000.0],
  PARAMETER[&quot;false_northing&quot;, 0.0],
  UNIT[&quot;m&quot;, 1.0],
  AXIS[&quot;Easting&quot;, EAST],
  AXIS[&quot;Northing&quot;, NORTH]]</mapProjection>
      <alignToStandardGrid>false</alignToStandardGrid>
      <standardGridOriginX>0.0</standardGridOriginX>
      <standardGridOriginY>0.0</standardGridOriginY>
      <nodataValueAtSea>false</nodataValueAtSea>
      <saveDEM>false</saveDEM>
      <saveLatLon>false</saveLatLon>
      <saveIncidenceAngleFromEllipsoid>true</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>

This was generated in the SNAP GUI with a belgian tile (UTM zone 31N), now if I take the same graph, change the read and write filenames (with a script, not the GUI) in order to process a tile in another UTM zone, if I run gdalinfo on the processed product I see that it’s in UTM 31N…
What I would like to do is process a batch of files from different UTM zones, and have gpt figure out the correct UTM zone for the projection, without going through the GUI.
Another way to do this would be reading metadata from my GRD product and figure out the correct UTM zone from the geo location, and then automatically substituting the WKT string in the xml graph with a script.
I am trying to understand if it’s possible to achieve this in a simpler manner using AUTO UTM…