{"id":2979,"date":"2019-07-25T16:40:36","date_gmt":"2019-07-25T14:40:36","guid":{"rendered":"https:\/\/blogs.fu-berlin.de\/reseda\/?page_id=2979"},"modified":"2019-08-22T15:56:36","modified_gmt":"2019-08-22T13:56:36","slug":"quality-band","status":"publish","type":"page","link":"https:\/\/blogs.fu-berlin.de\/reseda\/quality-band\/","title":{"rendered":"Cloud Masking for Sentinel-2 images"},"content":{"rendered":"

If there are clouds or cloud shadows on your sentinel-2 scene, they can be mask out using the quality scene classification band<\/em> of your scene.
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Sentinel-2 scene (true color) with clouds and cloud shadows<\/span><\/div>\n
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Image quality band and the classes we want to delete for our mask (Values): 3 (cloud shadows), 7 (unclassified), 8 (cloud medium probability), 9 (cloud high probability), 10 (thin cirrus) and 11 (snow or ice). For other scenes, you have to adjust the classes if necessary.<\/p>\n

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Sentinel-2 scene with quality scene classification<\/span><\/div>\n
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Here<\/a> you can download a Sentinel-2 image for executing this pre-processing step. For the scene which we used in the pre-processing before is no cloud correction necessary.<\/p>\n

Processing steps in RStudio:<\/strong><\/h1>\n

Open R-Studio and install, open the required packages and set your working directory:<\/p>\n

install.packages(\"raster\")\r\ninstall.packages(\"rgdal\")\r\n\r\nlibrary(raster)\r\nlibrary(rgdal)\r\n\r\nsetwd(\"D:\\\\elearning\\\\exchange\\\\R\")<\/pre>\n
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Open and plot the image:<\/p>\n
sen2 <- stack(\"subset_0_of_S2A_MSIL2A_20190626T102031_N0212_R065_T32UQD_20190626T125319_resampled.tif\")\r\nplot(sen2)\r\nplotRGB(sen2, 4,3,2, stretch=\"lin\")<\/pre>\n
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Seperate spectral bands and classification (band 1 to 12 is the mulispectral Senitnel- 2 scene, band 13 is the quality classification band):<\/p>\n
sen2_bands <- sen2[[-13]]\r\nsen2_mask <- sen2[[13]]\r\nplot(sen2_mask)<\/pre>\n
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Which pixels do we want to mask?<\/p>\n
plot(sen2_mask)\r\nsen2_mask_combi <- sen2_mask\r\nsen2_mask_combi[sen2_mask == 3 |sen2_mask == 7 |sen2_mask == 8 | sen2_mask == 9 |sen2_mask == 10 |sen2_mask == 11 ] <- NA\r\n\r\nplot(sen2_mask_combi)\r\nwriteRaster(sen2_mask_combi, \"sen2_mask.tif\")<\/pre>\n
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Mask without the classes: 3,7,8,9,10,11
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Apply mask:<\/p>\n
sen2_bands_masked <- raster::mask(sen2_bands,sen2_mask_combi)\r\nplotRGB(sen2_bands_masked, 4,3,2,stretch=\"lin\")\r\nwriteRaster(sen2_bands_masked, \"sen2_masked.tif\")<\/pre>\n
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Applied mask
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…or the whole part in short:<\/p>\n
sen2_bands_masked_a <- sen2_bands\r\nsen2_bands_masked_a [sen2_mask == 3 |sen2_mask == 7 |sen2_mask == 8 | sen2_mask == 9 |sen2_mask == 10 |sen2_mask == 11 ] <- NA\r\nwriteRaster(sen2_bands_masked_a, \"sen2_masked_alternativ.tif\")<\/pre>\n
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NEXT<\/em><\/strong><\/span>
\nSAR DATA<\/em><\/strong><\/span><\/a><\/div>\n
 <\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
If there are clouds or cloud shadows on your sentinel-2 scene, they can be mask out using the quality scene classification band of your scene. Sentinel-2 scene (true color) with clouds and cloud shadows Image quality band and the classes we want to delete for our mask (Values): 3 (cloud shadows), 7 (unclassified), 8 (cloud … Continue reading “Cloud Masking for Sentinel-2 images”<\/span><\/a><\/p>\n","protected":false},"author":3432,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-2979","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/pages\/2979","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/users\/3432"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/comments?post=2979"}],"version-history":[{"count":33,"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/pages\/2979\/revisions"}],"predecessor-version":[{"id":3061,"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/pages\/2979\/revisions\/3061"}],"wp:attachment":[{"href":"https:\/\/blogs.fu-berlin.de\/reseda\/wp-json\/wp\/v2\/media?parent=2979"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}