Module 8- Isarithmic Maps

This week covered isarithmic maps and I have to say this was my favorite section so far. I'm not sure if it was the weatherman aspect or the fact that this topic was easy to understand but I definitely enjoyed it. For the my lab I used ArcMap to create two maps depicting the average rainfall in Washington using the same precipitation raster dataset. The raster data came from the U.S. Department of Agriculture but was originally produced by the PRISM Group out of the University of Oregon. PRISM is an analytic method used to interpolate point data including the climatological affects of terrain features. This means the precipitation values that were assessed for areas without measuring points were based off of surrounding precipitation measurements as well as the mountains and hills in the region.

The first map displays the data using continuous tone shading. The shading was done using Stretched Symbolgy with the precipitation color ramp in the data's properties. I think this map is better suited for displaying the precipitation values because the changes look natural and smooth. As for the graphic, I used a dark background with light text because it was easier to see the edges of the map against the dark colors; all of the colors besides the map itself are somewhere in the gray scale.

Continuous Tone

The second map displays the precipitation data using hypsometric tinting with contour lines. I created the hypsometric tinting by using a Classified Symbology with the precipitation color ramp in the data's properties. I created ten classes and manually set the class boundaries. This created a map with color blocks of related colors. After classifying the data I also created contour lines using the Contour List Tool in the ArcToolbox. This tool requires the Spatial Analyst Extension to be enabled before you can use it but once it is turned on, it is fairly easy to use. To create the contour lines you simply add the original raster data to the Input section, select the Output location (place to save it), and then add the values you want contour lines drawn at. My contour lines were drawn at the class boundaries for the hypsometric tinting which makes the color changes even more defined.

 

Hypsometric Tinting with Contour Lines

Both maps also use a hillshade to give an idea of what the terrain looks like. I think that is important for these graphics because the dataset was interpolated with respect to these features.