I am using Arc 9.3 and have downloaded DEM data from the USGS seamless server for northern New Mexico. When I run the hillshade function after projecting the original DEM from GCS NA 1983 to UTM NAD 1983 Zone 13, I get these strange lines all over my hillshade that have a skewed grid pattern. They are all over and a quite closely spaced.
The hill shade looks fine without the transformation when I use the correct z factor, so I am pretty sure it is not the data itself. I am not using any geographic transformation during the conversion, so that may be it. Any recommendations or advice would be appreciated.
Without a screenshot to go off of, it sounds like you may have used Nearest resampling when you projected the data. Try projecting the original file again, but make sure you set the resampling to Bilinear.
