I have three municipalities with a total surface of 178 sq km. I want to analyze land cover of those municipalities using both LANDSAT images with a pixel size of 30 x 30 meters and SPOT with a pixel size 10 x 10 meters.
I have a raster of a whole county (> 1000 sq km) with land cover info derived both from LANDSAT and SPOT. When I clip the whole county raster with polygons of three municipalities, in case of clipping SPOT-based raster I get the correct surface of 178 sq km. That is the clipped raster area, the same as the surface of the three polygons/municipalities I am cutting with
If I clip the LANDSAT raster, the surface is 25% smaller, according to the attribute table! I know there should be differences because the pixel size is not the same and on the edges of the polygon I am cutting with some small discrepancies will appear. But what happened with the 25% of the surface?
I really have no clue what to do, I have done such things before, but never had such different results. Could it be something wrong with the data in the attribute table? (Even though I don't know what). Thank you in advance.