Hi,
I am extracting from a raster data set by mask with a polygon shape file as the mask - but the strange thing is that the masked raster data seems to have changed the values of raster data. For example, I know that within this polygon that there are many zero values, but these all disappear when I mask out the area with the polygon. Can anybody tell me what might be happening here? (by the way, a friend of mine seems to be doing the same thing with the same data, but not does not have the problem).
thanks
eric