DEM Mastery - 02/13/22

Lab Objectives

• Compare DEM sources

After sourcing four different DEM resolution from two separate sources (USGS & Utah AGRC) I was able to evaluate the difference in quality of data and major pros and cons. The first major difference is in the file size, the smaller of resolution you source the more dense the files will become in order to cover any substantial areas, this is something to be mindful of when looking at the scale of your project. The second major difference is in the way the DEM is sourced; for example Lidar is able to produce a high resolution DEM without detecting obstacles like clouds and vegetation as opposed to the photogrammetry which acts as a first response DEM based on linking aerial photographs together. The major cons with photogrammetry are the inconsistencies in data when obstacles are obstructing the view and the inability to look at bare ground elevation.

• Source, upload, and verify data

Based on the two sources of data two distinct resolutions were able to be sourced. USGS provided coarser resolution DEMs which required resampling in order to translate them to a coordinate system that correlated to the Utah AGRC DEMs. The newly projected data appeared very similarly to the imported Utah AGRC data, with no dark shading or lines to indicate a poorly project raster. Additionally, USGS provided metadata that could be read which allowed me to verify the source and understand that this was in-fact the correct data, prior to adding hill-shade it was difficult to distinguish between the two data-set so this was helpful

• Using Arc tools to highlight differences in DEM resolution

By adding hill-shade and contour to the map the differences in resolution became more distinct. The 5 m DEM showed very "detailed" elevation indicating the vegetation response, while the three others should a smoother surface due to the bare ground response. Adding contour lines also assisted in understanding how vastly different a .5 m vs. 30 m dem, after adding the contour lines I was able to scroll around high elevations and the lines based on the .5 m was able to follow the details in elevation of the ground more closely.

• https://drive.google.com/file/d/1Aze9vudQNi3vhq3R5c6lbpEqdd_KEF0z/view?usp=sharing