Module 2.1: Surfaces - TINs and DEMs

    In this week’s lab, I explored triangulated irregular networks (TINs) and digital elevation models (DEMs) as elevation surfaces. I started the lab by learning about how to include an elevation layer within a local scene to give a landscape a 3-dimensional appearance. I also altered settings which improved the 3D appearance.  

    In the next part of the lab, I explored DEMs more and used a DEM to create a suitability model for a ski run. New raster layers for the slope and aspect can be generated using a DEM raster. Using those new layers, I assigned a suitability score for certain data ranges and then overlaid the layers to create the final suitability model output.

    Next, I learned more about the data that is stored in a TIN  In addition to elevation, a TIN stores aspect and slope data. The values for elevation, slope and aspect for any given triangle can be accessed by clicking on it. They can also be visualized by altering the symbology of the TIN; edges and contours can also be visualized.

    In the last part of the lab, I learned about creating contours from a TIN and a DEM. Source points containing elevation data were then used to create a TIN and a DEM layer. From there two sets of contours were created, one from the TIN and another from the DEM. 

    The difference in the shape of the contours was probably most noticeable at the top of some of these crests and higher elevation points. Again, the TIN generated contours appeared jagged whereas the DEM generated contours appeared smooth. In some cases, the shape of the contours was totally different for each of them. The difference between the contours was the smallest along the slopes of the canyon side. While there were still noticeable differences in the shape, the contours align more closely. If using the contours on a map, I would probably use the DEM generated contours. Those contours are smoother and less distracting. Additionally, the difference in the accuracy is likely minimal given recent improvements in elevation data. I have attached the contour output for TIN and DEM generated contours so you can see the differences.

TIN Contour

DEM Contour