Module 3 of GIS 6005 - Communicating GIS was an exploration of various methods used to convey three-dimensional terrain on a two-dimensional map. The first exercise was a combination of contour lines and hypsometric tinting to illustrate how the rapidly the elevation changes throughout the mapped study area. Contour lines are 'lines of equal elevation above a datum. If a contour was actually drawn on the earth, it would trace a horizontal path that is constant in elevation [Kimberling, 2012, p. 217]. Additionally, hypsometric tinting is 'a method of "coloring between contour lines" that visually enhances the relative elevation cures for contours while maintaining the absolute portrayal of relief [Kimberling, 2012, p. 220]. A shown in the map below, the shades of the color ramp in the legend directly coincide with the elevation provided [in meters above sea level] at each contour line. For the symbology of the hypsometric tint, a green was used for the lowest elevations, which suggest a valley, and oranges / yellows for mid-elevations, and white for the highest, suggesting white capped mountains; this was the color scheme that was suggested in [Kimberling, 2012].
For the second a third portion of the lab, traditional and multi-directional hillshading effects were employed to actively display dimensionality on a printed terrain. Hillshading, or relief shading, uses a simulated light-source to provide relief on a map; however, the use of a singular light source creates overdeveloped, illuminated surfaces and dark, overbearing shadows. The solution to this problem is to utilize multiple light sources which will effectively reduce these extreme lighting characteristics found in traditional hillshading. The map below is a land classification map of a study area located in Yellowstone National Park. As shown in the legend, there are many various vegetation types that can be found on the map. To give the user a sense of depth and relief, a multi-directional hillshade effect was applied to the Digital Elevation Model and the land classification layer's transparency was set to 50%. This allows the texture of the landscape to be experienced by the viewer as they gather information on vegetation types found throughout the study area.
Part four of the lab was 'draping' a remotely sensed RaDAR imagery over a Triangulated Irregular Network Digital Terrain Model to give three-dimensionality to the orthophotos. The RaDAR imagery was gathered from a portion of Death Valley, California and can be seen in the image below.
This lab was a great opportunity to explore some techniques to give depth / relief to a two-dimensional map. A lot of material was covered in the text that we did not apply in the lab, but this assignment did provide a great foundational knowledge for future applications.
Informational sources:
Kimberling, A.J. (2012). Map Use: Reading, Analysis, Interpretation (7th edition). ESRI Press Academic.
No comments:
Post a Comment