Module 2.1: TINs and DEMS

The topic for this week's lab was working with 3D data in the form of DEMs or TINs. There were several parts to the lab, each with a different set of data and scenario. Local 3D scenes were created for each scenario by setting the raster elevation dataset as the surface source and setting a vertical exaggeration to show the differences in elevation changes better. 

Part A simply involved draping a terrain image over a 3D terrain to produce a realistic-looking 3D image. 

Part B involved taking a DEM, or Digital Elevation Model, raster and determining the potential suitability for a new ski slope location. The most suitable areas are areas at elevation above 2501 ft, a slope between 30-45 degrees, and the slope is heading in a western direction. In order to determine the suitability, the DEM was reclassified into three categories with rating values. The SLOPE tool was then used to create a slope raster with the elevation DEM as the input feature. This slope raster was also reclassified into five slope degrees categories, with rating values. Low slope values were rated the lowest. The ASPECT tool was also used with the elevation DEM, and the resulting raster was reclassified similarly to the elevation and slope data. Finally, the WEIGHTED OVERLAY tool was used to determine the suitability by weighing the ratings of all three combined rasters, in which the aspect is 25%, the elevation rating is weighted 40%, and the slope is weighted 35%. A higher weighted percentage essentially puts the rating as "higher priority" for that category. So, in this case, the elevation had the highest priority. The final suitability raster is pictured below, using the draping and vertical exaggeration method in a 3D local scene. Areas ranged from dark green (very suitable) to red (unsuitable). 

Part C worked with a TIN surface by changing/modifying the appearance, creating contours, slope, and  aspect using the TIN Layer symbology tab. 

Finally, Part D data included a set of elevation points. A TIN raster was created from these elevation points using the CREATE TIN tool and the SPLINE tool was used on the same elevation point dataset to create a DEM raster. Then, both were symbolized to show contour lines in order to compare the differences between the two methods. I observed that the TIN-derived contours are more angular than the DEM-derived contours in areas where there are curves or peaks in elevation. Also, since the DEM seems to show more of a extrapolated, smoothed contour set, the TIN dataset seems to be more accurate at representing elevation changes.