I've been playing around a bit with the
USGS National Map Viewer, and I'm trying to get a sense of where the data is coming from.
The contour intervals shown on the digital National Map, say 20 feet, match up with the previous paper versions. The hill shapes are generally the same, too. But in the areas where I'm looking (central Washington state), the old paper versions show more contour detail (smaller hills and depressions) than the newer digital contours do. Where did the detail go?
A related question has to do with the data used to create the hill shading. The National Map seems to agree with what's shown in Google's Terrain View. But in an area where I'm looking, the hill shading has more detail than the contours of the National Map, but it doesn't quite match up with the older paper versions. Where is this detail coming from?
I haven't played around with the GIS downloads yet, but if I were, which version of the terrain would I get? Something closer to the original paper, or the National Map contours, or the hill shading?