I am working with some Landsat 7 and 8 imagery, as well as Sentinel imagery. I have heard that you should use images that contain less then 20% cloud coverage, but am having trouble finding articles that can justify this number. I am working on writing a paper and need to be able to cite why I picked the number.
Dear Zach,
Thank you for your question. Although Landsat and Sentinel imagery data would be adequate for many studies because of the temporal observing frequency (16-day) and pixel resolution of 20-30 m, cloud cover is a limiting factor to obtaining frequent and bulk of images, especially for the rainy seasons. In my opinion, selecting the scene depends on your RS application that you are going to apply. There is no solid percentage (e.g. 20%) for the selection of such a scene. In my works for water resources management, I utilized Landsat images with cloud cover ≤5% (e.g. Article Implications of non-sustainable agricultural water policies ...
) and others use different percentages. If I were you, I would try to find many of published papers relevant to your application works which selected a cloud cover scene
Dear Zach Leslie,
Long answer short, when you download LANDSAT or SENTINEL imagery from USGS' Earth Explorer try to go for the lowest cloud cover possible. Normally, researchers under any application try to minimize, or even completely remove cloud cover. Personally, I don't think you need to justify your choice for low cloud cover because the matter is quite obvious. If seasonal variations are not a target in your study try downloading images outside the rainy season for your study area. The number 20% is not a fix threshold for cloud cover. Keep in mind that this percentage depends on the size of your study area (a 20% cloud cover on small watersheds let's say can be a problem, while for large study areas 20% is not that big of a problem). However, again, based on my personal experience, it's not that urging to cite references for justifying the low cloud cover option, it's a generally acceptable and accepted fact.
Good luck,
Mario
Hi,
It depends on the application. As siad earlier, you don't need a reference for could cover. Generally, avoid images with cloud cover. 20% cloud cover is also relative. If the 20% does not affect your output, then, it is fine. But if it does, please chose a scene with lesser or no cloud cover
Excellent answers Islam Sabry Al Zayed , Mario Al Sayah and Oluwafemi Adeyeri ... Thank you all.
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