I need to create 3 Digital Elevation Models for separate locations in Southern Ontario. The areas are large enough that it requires several DEM tiles (7 or so) to cover the area. I need to create 1 seamless DEM (for each study area) to complete further analysis (hillshade, aspect, slope, etc.). I thought I had finally successfully mosaiced the DEMs together (I created a File Geodatabase and within that a Raster Dataset and loaded all the rasters into it). It created one seamless DEM with an elevation range of 193 to 239 meters. However, when I used the 'Extract by Mask' tool (so that I only had the study area), the resulting DEM had an elevation range of 163 to 314 meters. That seems impossible; how can the elevation range increase when decreasing the area!?
However, upon further investigation... I used to Identify tool to click around some of the high and low spots on the original mosaiced DEM and found that those higher and lower elevations (outside of what the statistics and symbology were telling me existed for that file (ex. 163m and 312m, etc.)). And also, the masked DEM does not have the greater elevations that it says it does (that actually do exist on the original, full DEM). Why is Arc giving me an incorrect range of elevation values?
Any help would be greatly appreciated.
Thanks so much!
Sarah
