GIS5935 Lab 13: Effects of Scale

This analysis consisted of comparing two DEMs, one from LIDAR and one from SRTM. Both were set to the same coordinate system and the same cell size of 90 meters, then compared a number of ways. To compare the two DEMS, I first looked at the differences in elevation and slope. I checked the minimum and maximum elevation for each one, as well as the minimum, maximum and average slope. I also compared the aspect of each of them to find any major differences in the direction that each cell faced.

The slope and elevation differences can be seen here:

	LIDAR	SRTM
Maximum Elevation	1063.67	1053
Minimun Elevation	4.31	12
Maximum Slope	50.46	45.77
Minimum Slope	0.89	1.53
Average Slope	29.65	27.49

The differences in aspect can be seen in this comparison:

The comparison of the two DEMs resulted in a slight, noticeable difference in each area. For example, the maximum elevation for the LIDAR data was 1063 meters, while the SRTM data was ten meters lower at 1053. The minimum elevations were also 4.3 and 12 meters, respectively. The image above also shows the differences in aspect that can be seen throughout each DEM. These can possibly be explained by how each DEM was developed. Since the LIDAR data was developed from instruments much closer to the ground than the SRTM (which was collected from a space shuttle), subtle differences in aspect are bound to arise.

 There was also a slight difference in slope between the two, LIDAR having an average 29.65 degree slope and SRTM having a 27.49 degree slope. This again could probably be attributed to how each set of data was developed. Given how the ground is detected using LIDAR at a much more specific level, as opposed to SRTM, which was an entire earth-encompassing project, there is likely to be a little more generalization throughout the STRM data. The higher slope average of the LIDAR data suggests slightly less generalization and therefore slightly more accuracy.