I am attempting to make a set of large hillshades in ArcMap for California (split into 6 zones). I downloaded 10m DEMs for every county from NED. I created mosaics for each county, and then mosaicked groups of counties into larger regions. I then ran the hillshade tool (with default settings) for each region, but ran into this grid issue (see screen shot).
The grid only appears where I believe there are differences in origin coordinates systems. The DEMs are split into UTM zone 10 and 11 across the state, and I think the merging of these is causing the issue. In one of my hillshades, where all the DEMs are in zone 11, the problem doesn't occur.
Any advice on how to fix this? I've tried re-projecting my mosaics into WGS 84 and haven't had luck. Should I start from scratch and project all of the original DEMs into the same coordinate system before mosaicking them? If yes, is there a less-than-cumbersome way to do this? California is a big state.