Difference between revisions of "Clip Sentinel-2 images"
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| − | == | + | == Create a Band set (virtual raster) with Sentinel images == |
Now that we have both the study area polygon and the Sentinel-2 images stored on a folder, we clip all the images to make its processing faster. | Now that we have both the study area polygon and the Sentinel-2 images stored on a folder, we clip all the images to make its processing faster. | ||
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| + | == Create a second Band set (virtual raster) with Landsat 8 images == | ||
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| + | [[File:Captura de ecrã de 2018-06-07 11-36-48.png]] | ||
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| + | == Clip Band sets == | ||
Revision as of 09:38, 7 June 2018
Sentinel-2 images are large and have many bands. We can minimize the processing time by restricting the images to the area we want to work on.
For this exercise, we can use the GADM data. Download Denmark's data from https://gadm.org/download_country_v3.html Or use this direct link: [1]
Create the polygon
From gadm36_DNK_2, create a unique polygon containing the 4 municipalities (kommuner):
- Hillerød,
- Helsingør,
- Gribskov,
- Fredensborg
Save the layer (using shapefile format) using EPSG:32633 as the CRS, to match the same CRS as the Sentinel-2 images we have.
Clipping polygon
The resulting layer "studyarea" should look like:
Create a Band set (virtual raster) with Sentinel images
Now that we have both the study area polygon and the Sentinel-2 images stored on a folder, we clip all the images to make its processing faster.
To clip all the images, we use the SCP plugin → Preprocessing → Clip multiple rasters.
The clip tools needs a Band set to operate on. Since we will not use some bands (1, 9 and 10), we can create a band set without them.
The new Band set is added to QGIS layers.
It is added with a default style. The default style uses the first 3 bands as the RGB bands. So, band 1 is used as Red, 2 as Green and 3 as Blue.
Change the style definition, to show the first 3 bands, but by a different order.
Remember that we are not using band 1, so our band 1 is in fact Sentinel band 2.
| Sentinel-2 Bands | Central Wavelength [micrometers] | Resolution [meters] |
| Band 1 - Coastal aerosol | 0.443 | 60 |
| Band 2 - Blue | 0.490 | 10 |
| Band 3 - Green | 0.560 | 10 |
| Band 4 - Red | 0.665 | 10 |
| Band 5 - Vegetation Red Edge | 0.705 | 20 |
| Band 6 - Vegetation Red Edge | 0.740 | 20 |
| Band 7 - Vegetation Red Edge | 0.783 | 20 |
| Band 8 - NIR | 0.842 | 10 |
| Band 8A - Vegetation Red Edge | 0.865 | 20 |
| Band 9 - Water vapour | 0.945 | 60 |
| Band 10 - SWIR - Cirrus | 1.375 | 60 |
| Band 11 - SWIR | 1.610 | 20 |
| Band 12 - SWIR | 2.190 | 20 |
Create a second Band set (virtual raster) with Landsat 8 images
