Spatial subset
From AWF-Wiki
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# Click the {{button|text=Add raster layer}} [[Image:QGIS_2.0_addrast.png|20px]] and select the file ''/geodata/raster/s2/Subset_S2A_MSIL2A_20170619T_MUL.tif''. | # Click the {{button|text=Add raster layer}} [[Image:QGIS_2.0_addrast.png|20px]] and select the file ''/geodata/raster/s2/Subset_S2A_MSIL2A_20170619T_MUL.tif''. | ||
# After clicking {{button|text=Open}}, the raster layer appears on the QGIS canvas. | # After clicking {{button|text=Open}}, the raster layer appears on the QGIS canvas. | ||
− | # {{mitem|text=Raster --> Extraction ---> | + | # {{mitem|text=Raster --> Extraction ---> Clip Raster by Extent}} |
# Input file (raster): Choose a loaded file name fron the drop down list or click {{button|text=Select}} to browse a file. | # Input file (raster): Choose a loaded file name fron the drop down list or click {{button|text=Select}} to browse a file. | ||
# Output file: click {{button|text=Select}} to choose a new file name for the subset image. | # Output file: click {{button|text=Select}} to choose a new file name for the subset image. | ||
− | # | + | # Defien the clipping extent by clicking{{button|text=...}} and '''Select extent from canvas''' The clipping mode is now 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 | + | # Adjust the extent coordinates in the text file rounding the coordinates upper left lower right x, y coordinates. |
[[File:Qgis_raster_clipper.png|600px]] | [[File:Qgis_raster_clipper.png|600px]] | ||
# Click {{button|text=OK}}. | # Click {{button|text=OK}}. |
Revision as of 20:58, 21 October 2018
Interactive box selection
- Click the Add raster layer and select the file /geodata/raster/s2/Subset_S2A_MSIL2A_20170619T_MUL.tif.
- After clicking Open, the raster layer appears on the QGIS canvas.
- Raster --> Extraction ---> Clip Raster by Extent
- Input file (raster): Choose a loaded file name fron the drop down list or click Select to browse a file.
- Output file: click Select to choose a new file name for the subset image.
- Defien the clipping extent by clicking... and Select extent from canvas The clipping mode is now 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 upper left lower right x, y coordinates.
- Click OK.
Vector polygon masking
- 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 from Extent to Mask. 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 and specify the value 0.
- Click OK.