I have some 1/3 arc sec data from USGS seamless data server (datum = D_North_American_1983) for San Francisco South and nearby quadrangles. I can create a reasonable hillshade using a z factor of 0.00003 and everything looks fine. However, to create a slope map, it appears that I need to change the projection to UTM. When I project the data in NAD_1983_UTM Zone_10N, I get east-west and north-south artifacts in the hillshade and slope maps (see sample image). [ATTACH=CONFIG]12902[/ATTACH] . Does anyone know how to avoid having those artifacts or what is causing them? Are these data somehow nor compatible with the projection tool?