Spatial subset
From AWF-Wiki
(Difference between revisions)
(→Interactive box selection) |
(→Vector polygon masking) |
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# Click {{button|text=OK}}. | # Click {{button|text=OK}}. | ||
| − | = | + | = Masking by vector polygon= |
* Load the vector file ''\geodata\vector\gadm36_DEU_4.shp''. These are the level 4 administrative boundaries of the country Germany downloaded from https://gadm.org/index.html . | * Load the vector file ''\geodata\vector\gadm36_DEU_4.shp''. These are the level 4 administrative boundaries of the country Germany downloaded from https://gadm.org/index.html . | ||
* Right click on Layer name in the Layers Panel {{mitem|text=Properties --> General}}. Change the '''Data source encoding''' from {{button|text=System}} to {{button|text=UTF-8}}. Click {{button|text=UTF-8}}. | * Right click on Layer name in the Layers Panel {{mitem|text=Properties --> General}}. Change the '''Data source encoding''' from {{button|text=System}} to {{button|text=UTF-8}}. Click {{button|text=UTF-8}}. | ||
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# 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 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 '''Keep resolution of output raster''' on. | # Switch '''Keep resolution of output raster''' on. | ||
| − | # Choose output data type {{typed|text=Uint16}. | + | # Choose output data type: {{typed|text=Uint16}}. |
# Click {{button|text=Run in Background}}. | # Click {{button|text=Run in Background}}. | ||
| − | [[File:Qgis_raster_mask.png| | + | [[File:Qgis_raster_mask.png|700px]] |
[[Category: Working with Raster Data]] | [[Category: Working with Raster Data]] | ||
Revision as of 12:54, 29 October 2018
Interactive box selection
- Click the Open Data Source Manager
and Add raster layer 
and select the file /geodata/raster/s2/Subset_S2A_MSIL2A_20170619T_MUL.tif.
- Raster --> Extraction ---> Clip Raster by Extent
- Input file (raster): Choose a loaded file from the drop down list or click Select to browse for a file.
- Output file: click Select to choose a new file name for the subset image.
- Define 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 and lower right).
- Click OK.
Masking by vector polygon
- Load the vector file \geodata\vector\gadm36_DEU_4.shp. These are the level 4 administrative boundaries of the country Germany downloaded from https://gadm.org/index.html .
- Right click on Layer name in the Layers Panel Properties --> 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 . Export --> Save Features as... Save as.... Fill the form as shown below.
- Click the checkbox Save only the selected features.
- The target coordinate reference system (CRS) is WGS84 / UTM zone 32 (EPSG:32632).
Make sure that the CRS is the same like the image file (here WGS84/UTM Zone 32, EPSG:32632)!
- Click OK.
- Raster --> Extraction ---> Clip Raster by Mask Layer...
- Input file (raster): Choose a loaded file name from the drop down list or click Select to browse to a file
- Mask layer: Select the exported vector file (s. above).
- Clipped (mask)): click Select to choose a new file name for the subset image.
- 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 Keep resolution of output raster on.
- Choose output data type: Uint16.
- Click Run in Background.
