A. Starling's GIS Blog

                In this lab, we explored two types of elevation data models - Digital Elevation Model (DEM) and Triangulated Irregular Network (TIN). The DEM is raster-based and information is stored in grid format, while TIN is vector-based and uses irregularly spaced points that were calculated according to the connections of sets of triangles for contouring. Because of this, the DEM has smoother curves in its contour lines, while TIN has pointed/jagged contour lines. The DEM contour lines in this instance also have a few more lines due to the data parameters.                 The TIN contour lines are likely more accurate, as TIN can differentiate between more complex terrain than DEM contour typically can (depending on resolution). TIN uses irregularly placed elevation points that vary based on data density, but DEM is a grid with elevation values stored within the grid cel...

     The goal of the analysis for this week’s study on accuracy assessment was to determine which dataset, TIGER Roads or Street Centerlines, were more complete for Jackson County, Oregon.  In this lab, we are measuring completeness using the assumption that the more road there is, the more complete it is.      We could use the length of the roads to determine completeness. After ensuring data was in the same projection, we looked at the statistics (Attribute Table -> Visualize Statistics) to determine the sum of the road segment lengths: Street Centerline : 10873.3 km TIGER Roads : 11382.7 km Because this lab measures completeness based on road length (the more road there is, the more complete it is) – in this case, TIGER Roads is more complete than Street Centerline. We went a little further in this lab to determine length of roads with each grid of Jackson County, Florida – see Map 1: Map 1: Percent Difference of Road Length between TI...