1

I am wondering the best way of knowing how to define the area of each raster cell in global data. Specifically, I downloaded all ~400 tiles of MODIS land cover data, mosaiced them into one, and now am summarizing land cover areas at admin levels. The data come downloaded as custom spheroid sinusoidal (~463m resolution). Each subset appears to contain cells all of the same size. My question is after I mosaic the data into one raster, if I changed the projection to WGS84, would I then have to account for the cell sizes changing with latitude? Does it depend on what the projection the original data were in? I can't think of any way to test this, since when looking at the data in ArcMap the cells all measure the same, using the measure tool, which may or may not just be a product of the dataframes coordinate system. Would converting a subset of the raster to shapefile and then calculating the area tell me anything?

Overall my question is a basic one, does every raster in a geographic coordinate system by its nature have cell sizes that change with latitude? Or are there exceptions?

  • Would converting a subset of the raster to shapefile and then calculating the area tell me anything? Try a small area near the north pole and an area hear the equator and let us know. – Paul H Feb 23 '16 at 16:49
  • @PaulH The result shows that the cell areas are the same, or close enough to the same using this method. Is this a good way of determining cell area do you think? So, if this is correct, I would conclude that for the most part the original projection from which the raster data was assembled will dictate its cell areas. – timpjohns Feb 23 '16 at 19:23
  • Is this a good way of determining cell area...? -- Impossible to way without knowing what you did. – Paul H Feb 23 '16 at 19:37
  • I did what you suggested, what do you mean you don't know what I did? I figured you'd have some input since you wanted to know what the results were. – timpjohns Feb 23 '16 at 19:48
  • I don't know what commands you used, if you just traced a cell in a GUI, anything. I can't reproduce your work at all. – Paul H Feb 23 '16 at 19:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.