I have land use data from U.S.D.A. geospatial data gateway. I believe I read somewhere that the raster cell size is 30 m x 30 m. When I look in the Properties > Source > Raster Information, it says "Cell Size (X, Y) 31.871 , 31.871", I'm assuming that's in meters. I am trying to figure out approximate areas for several subsets of my map and want as close an estimate as possible. Can I consider it safe to do the math based on the 31.871 value and not 30?