Ex of source data artifacts causing false detection of vertical change

Example of source data artifacts causing false detection of vertical change. From left to right, images are NED shaded relief, SRTM shaded relief, SRTM NED difference grid (blue = significant decrease in elevation; red = significant increase in elevation), and areas of significant differences (outlined in yellow) overlaid on NED shaded relief. There are no actual topographic changes in this area in eastern Wyoming. Note that the areas of significant differences are located over artificial highs and lows in the NED due to production artifacts in the original USGS DEM source data. The area shown is about 12.8 km east-west by 27.7 km north-south.

More information can be found on the Significant Topographic Changes in the United States website.