Confusion arises when subsetting sentinel-1 image based on geographic coordinates with subset tool using graph processing tool

Dear,
I’m trying to create subset of sentinel-1 images (have been terrain corrected, of course) based on geographic coordinates with subset tool in graphbuilder tool. I find it extract the region I want, BUT the geographic coordinates of the output image is wrong.
The correct geographic coordinates I want and I enter is:
POLYGON ((-81.520 43.466, -81.143 43.466, -81.143 43.118, -81.520 43.118, -81.520 43.466, -81.520 43.466))
but the output image’s geographic coordinates is:
POLYGON ((-82.249 44.193, -81.872 44.193, -81.872 43.845, -82.249 43.845, -82.249 44.193, -82.249 44.193))
Here is the graph’s xml file:

<?xml version="1.0"?>

-<graph id="Graph">

<version>1.0</version>


-<node id="Read">

<operator>Read</operator>

<sources/>


-<parameters class="com.bc.ceres.binding.dom.XppDomElement">

<file>F:\ARS\data_test\S1A_IW_GRDH_1SDV_20190105T231617_20190105T231644_025349_02CE49_30E4_NR_Cal_Deb_ML_Spk_SRGR_TC.dim</file>

</parameters>

</node>


-<node id="Subset">

<operator>Subset</operator>


-<sources>

<sourceProduct refid="Read"/>

</sources>


-<parameters class="com.bc.ceres.binding.dom.XppDomElement">

<sourceBands/>

<region>0,0,21245,12485</region>

<referenceBand/>

<geoRegion>POLYGON ((-81.5199966430664 43.465999603271484, -81.14299774169922 43.465999603271484, -81.14299774169922 43.11800003051758, -81.5199966430664 43.11800003051758, -81.5199966430664 43.465999603271484, -81.5199966430664 43.465999603271484))</geoRegion>

<subSamplingX>1</subSamplingX>

<subSamplingY>1</subSamplingY>

<fullSwath>false</fullSwath>

<tiePointGridNames/>

<copyMetadata>true</copyMetadata>

</parameters>

</node>


-<node id="Write">

<operator>Write</operator>


-<sources>

<sourceProduct refid="Subset"/>

</sources>


-<parameters class="com.bc.ceres.binding.dom.XppDomElement">

<file>F:\ARS\data_test\target.dim</file>

<formatName>BEAM-DIMAP</formatName>

</parameters>

</node>


-<applicationData id="Presentation">

<Description/>


-<node id="Read">

<displayPosition y="134.0" x="37.0"/>

</node>


-<node id="Subset">

<displayPosition y="148.0" x="259.0"/>

</node>


-<node id="Write">

<displayPosition y="135.0" x="455.0"/>

</node>

</applicationData>

</graph>
2 Likes

Hello,

I want to pre-process the Sentinel 1 Data (downloaded with peps) by using SNAP in the context of the detection of irrigated plots and crop monitoring for a Region Of Interest (ROI). The steps of Apply Orbit File, Thermal Noise Removal, Remove GRD Border Noise, Calibration and Terrain correction are mandatory for my study ? And in which step can I add the “Subset” operation in the Graph to study just a region (ROI). Shoud be after Apply Orbit File or after Terrain Correction.

Capture d’écran 2024-05-15 182752
Capture d'écran 2024-05-15 1827521347×229 22.4 KB

Thank you,