I used and 4.0 and 5.0 version of SNAP Toolbox. I applying following graph:
Read -> Apply Orbit File -> thermal Noise Removal -> Calibration -> Terrain Correction -> Read
I got a mean value of pixels from some image with X for Y resolution. Then I got the same image with another smaller resolution X/3 and Y/3 pixels. After, that I have calculated the average value of pixels from both images and I get different values. (e.g. values of pixels are from 0 to 10 and I got 3.5 and 3.8 (for smaller image)). Is it ok? If yes how much is mean squared error?
I cut this image by GDAL Python API by geojson.
I just change from 10 to 30.
<node id="Terrain-Correction">
<operator>Terrain-Correction</operator>
<sources>
<sourceProduct refid="Calibration"/>
</sources>
<parameters class="com.bc.ceres.binding.dom.XppDomElement">
<sourceBands/>
<demName>SRTM 3Sec</demName>
<externalDEMFile/>
<externalDEMNoDataValue>0.0</externalDEMNoDataValue>
<externalDEMApplyEGM>true</externalDEMApplyEGM>
<demResamplingMethod>BILINEAR_INTERPOLATION</demResamplingMethod>
<imgResamplingMethod>BILINEAR_INTERPOLATION</imgResamplingMethod>
<pixelSpacingInMeter>10.0</pixelSpacingInMeter>
<pixelSpacingInDegree>2.6949458523585647E-4</pixelSpacingInDegree>
<mapProjection>$projection</mapProjection>
<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>
Here is both output images.
