Lab 13 – Effects of Scale

Quantitatively, I compared the DEM elevation values directly, as well as two derivatives: Aspect and slope.  I first made both an Aspect and Slope surface for these DEMs.  I then used Batch processing for the Get Raster Properties tool selecting MINIMUM, MAXIMUM, and MEAN for each of the now six total rasters.

The elevation data comparison shows that the LiDAR DEM had a greater range of values compared to the SRTM DEM; the minimum value was smaller and maximum value was larger for the LiDAR DEM.  This may be an indication of greater elevation resolution.  The mean elevation value was lower for the LiDAR DEM.  Though these differences are apparent here, the magnitude of the difference is small and not likely significant. 

The slope and aspect summary statistics are highly similar between the two datasets as well.  The mean slope of the SRTM DEM is smaller, though this can be inferred based on the smaller range in elevations of this DEM.  It may be assumed that the LiDAR data is more accurate; however, the overall difference between the two datasets is very minimal.  I suspect the LiDAR dataset is more accurate for two reasons: First, it is the product of a resampling technique whereby the underlying accuracy of the high resolution 1-m DEM is certainly higher than the derive 90-m DEM.  Second, the SRTM DEM was created via orbital spacecraft, which, inherently introduces a higher degree of vertical measurement error.