I've been following this thread and decided to take a closer look at the SRTM data now that I just upgraded to 9.2. Perhaps someone has some suggestions on how to create a hillshade that looks like the .gif that is delivered with the data. The default hillshade I created looks pretty poor.
You can use the offset method but it is sketchy.
The process I used mainly because I was also calculating aspect and slope was to reproject the DEMs. However, ESRI's raster reprojection algorithm leaves a bit to be desired. It typically results in artifacting and yes I've tried several different methods. I use either of these two different methods of reprojecting depending on the project.
1) Purchase a tool that reprojects better. I use Global Mapper quite a bit for data conversion and it seems to reproject well. Its well worth the $250 versus the next process. I use Global Mapper a lot to downsample 30-meter DEMs to 90-meter and reproject to custom projections all the time. Great tool for working with large areas.
2) This requires Spatial Analyst and Arc/Info and I tend to use this process on smaller site specific projects.
- ArcGIS: Open your DEM and contour your DEM
- ArcGIS: Reproject the shapefile contours to the desired projection.
- ArcInfo: Convert shapefile contours to coverage
- ArcInfo: Create new DEM using TOPOGRID
There is a new tool in Spatial Analyst that replaces the TOPOGRID command but it can get flaky. I usually get a "Too many vertices" error and it bombs. There are a lot of little extras I might do depending on the project; smooth the contours, obtain point data for peaks and sinkholes, etc. I rarely use command-line ArcInfo anymore but keep it around just for the TOPOGRID command and a variety of AMLs I still use.