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I'm looking at land cover in an area of South East Asia. I pulled down Sentinel 2 imagery for Feb 2017, and used the QGIS SCP plugin to complete the land cover analysis, as per this tutorial: https://fromgistors.blogspot.com/2016/09/basic-tutorial-2.html. Wanting to better understand which areas of lesser growth were plant growth recovering from cultivation, and what were otherwise sparse forest, I took a look at some older satellite data, only to find it looked very different. I've included examples below using using Sentinel bands 4,8 and 12, all of which were processed in identical ways.

If this is indeed just a difference in the visual output of SCP/QGIS, I would love to know how to get them more comparable.

Jan 2016 enter image description here

Jan 2017 enter image description here

Feb 2017 enter image description here

  • did you check some other sources like google earth to see if this might me some fire incidents or intensification of land use? – LaughU Jul 26 '17 at 8:14
  • have you tried overlaying a NDVI band? – Alex Jul 26 '17 at 10:20
  • Can you be more specific about the location of study area? My guess would be snow cover – firefly-orange Jul 26 '17 at 10:44
  • To be clear, this is an RGB composite of 4-8-12? (R:band 4, G:band 8 and B: band 12) – Albert Jul 26 '17 at 11:15
  • @firefly-orange snow or cloud! you could also try using a NDSI – Alex Jul 26 '17 at 11:18
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As the comments suggesting, there are several explanations for this phenomena.

The most curial part is where in South East Asia is the location exactly.

I make my assumption based on this ESA source, the German wiki for sentinel 2 (here is the English one) and my general knowledge of Remote sensing.

  1. It could be a change in the way images are processed but I did not find any hints that there was a change.

  2. Comparing the images from 2016 and 2017 this could indicate an intensification of agricultural use of the area.

  3. The change between Jan. and Feb. might be harvest - or planting season.

  4. It could also either a fire event or snow fall. (Again depends on where we are to rule out this point)

  5. Change in the atmosphere because band 12 can be used to get aerosols and band 8 for water vapor(indicated in german wiki articel not in the english one).

  • Thanks for this. This is in Western Myanmar, so no snow fall. I'll have to investigate the likelihood of fire up there - particularly if farmers have been using slash and burn to clear ground. But what interests me is that the dull purple areas in the first images are much richer purple in the final one, where as I expected them to fade further over time, or bright pink if they were being cleared again for cultivation. So in the absence in changes to the Sentinel image processing, it could well be options 2, 3 or 5. Perhaps I'll try to compare against LANDSAT imagery. – Will Jul 26 '17 at 16:02
  • If the trees have leaves at that time, it may be the attack of some insects – nagib Sep 9 '17 at 16:38

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