DEM of Difference

Caption: Figures 1 and 2 demonstrate the differences in error between various digital elevation models (DEMs). Figure 1 illustrates the contrast between a high-resolution 1-meter lidar DEM and a 30-meter USGS 3DEP DEM. Figure 2 highlights the distinction between a precise 1-meter lidar DEM and a 5-meter autocorrelated DEM generated from NAIP imagery.  In both figures, areas depicted in green represent regions where the 1-meter lidar DEM indicates significantly higher elevations compared to the the contending DEM, while areas shown in purple indicate regions where the lidar DEM suggests lower elevations. The key difference between these DEMs is that the 1-meter lidar DEM in both cases, provides for a better depiction of sheer vertical cliffs.  Along the margin of these geologic features, a more distinct line of higher and lower elevations can be visualized with the lidar DEM, whereas with the 30-meter DEM, much of the margins along the geologic feature are blended together into multiple pixels, leaving the viewer unsure of exactly where these edge features are. This highlights the importance of choosing an elevation model with sufficient resolution to accurately capture these features. Additionally, it's worth noting that there was a much more substantial difference in the lidar DEM compared to the autocorrelated NAIP imagery. Even though a DEM product may be labeled as having a 5-meter resolution, sometimes when choosing between this and a 30-meter DEM, it might be best to use the broader scale DEM. The range of elevation differences between the 1-meter lidar and the 5- meter autocorrelated models are -59m to 138 m, whereas the range differences of 1-meter lidar and 30-meter 3DEP ranges from -62 to 71 m. For this area, all of the errors in elevation where confined to sheer vertical cliff walls, whereas slopes and valleys had little to no error.