Spatial subset

Revision as of 16:17, 25 October 2017

Click the Add raster layer and select the file C:/OSGeo4W64/geodata/raster/s2/Subset_S2A_MSIL2A_20170619T.tif.
After clicking Open, the raster layer appears on the QGIS canvas.
Raster --> Extraction ---> Clipper...
Input file (raster): Choose a loaded file name fron the drop down list or click Select to browse to a file.
Output file: click Select to choose a new file name for the subset image.
The clipping mode is now already active. Hold a left click on the map canvas dragging a box of your region of interest.
Adjust the extent coordinates in the text file rounding the coordinates of 1 (upper left corner) x, y and 2 (lower right corner) x, y.

Load the vector file C:\OSGeo4W64\var\geodata\vector\Landkreis_Goe_neu_utm32.shp. This is the actual boundary of the county Göttingen. We create a new vecto file with the boundary of the municipality Göttingen.
Right click on Layer name in the Layers PanelProperties --> General. Change the Data source encoding from System to UTF-8. Click UTF-8.
Right click on Layer name in the Layers Panel and open the Attribute table.
Click and select by the expression: "NAME_4" ='Göttingen'. Select.

Right click on Layer name in the Layers Panel Save as.... Fill the form as shown below.

Make sure that the CRS is the same like the image file.

Click Run.
Raster --> Extraction ---> Clipper...
Input file (raster): Choose a loaded file name fron the drop down list or click Select to browse to a file (see above).
Output file: click Select to choose a new file name for the subset image.
Change the clipping mode Extent to Mask. Hold a left click on the map canvas dragging a box of your region of interest.
Choose the newly created polygon of the municipality as Mask Layer.
Switch the checkbox on: Crop the extent of the target dataset to the extent of the cutline. All image data outside the polygon will be masked.
Switch the 'No data value checkbox on.
Click OK.

@@ Line 20: / Line 20: @@
 Make sure that the CRS is the same like the image file.
 # Click {{button|text=Run}}.
+# {{mitem|text=Raster --> Extraction ---> Clipper...}}
+# Input file (raster): Choose a loaded file name fron the drop down list or click {{button|text=Select}} to browse to a file (see above).
+# Output file:  click {{button|text=Select}} to choose a new file name for the subset image.
+# Change the clipping mode '''Extent''' to '''Mask'''. Hold a left click on the map canvas dragging a box of your region of interest.
+# Choose the newly created polygon of the municipality as '''Mask Layer'''.
+# Switch the checkbox on: '''Crop the extent of the target dataset to the extent of the cutline'''. All image data outside the polygon will be masked.
+# Switch the '''No data value'' checkbox on.
+# Click {{button|text=OK}}.
+[[File:Qgis_raster_mask.png|400px]]
 [[Category: Working with Raster Data]]