Cartography Week 6: Isarithmic Mapping

 

In this week's lab, we created a map of annual precipitation averages in Washington with hypsometric tints and contours. The weather and elevation data used to create this map is a 30-year climatological average from the period 1981-2010, and that dataset comes from the PRISM Group at Oregon State University and was published by the US Department of Agriculture. In my map, I included an explanation of the PRISM model that was used to interpolate annual precipitation averages for each pixel in the state of Washington.

I set the values for the contours manually according to the guidelines in the lab instructions, and I used the standard color scheme for precipitation maps. It was nice to make a really colorful map after weeks of following the traditional cartographic principle of avoiding rainbow colors! I chose a dark basemap to create a strong figure-ground relationship with the colorful map. We also explored continuous tone symbology in the lab, but I think this map looks a lot better with contours and discrete hypsometric tints. Previous to this lab, I had no idea how weather maps were created, so it was fun to learn about PRISM and typical weather map symbology. The lab was also simple enough that I could spend more time on the cartographic design and create a layout that I think is aesthetically pleasing.

This week, my boss at the farm I work at showed my coworkers and me a weather map from NOAA's Climate Prediction Center that he uses to decide when to plant certain cold-intolerant crops or how to protect them. The map predicts the probability that the temperature in the next 6-10 days will be above or below the average for the time of year, based on a 30-year climatological average. It uses contour lines and hypsometric tints for probability ranges on the large scale of the US, so it doesn't use the same kind of data or the same level of detail as the map we made for this lab, but it was interesting to see how climate maps created with GIS are used in the real world.

There is a 33-40% chance that the temperature in Virginia will be below normal for May 6-10, so my boss decided (in combination with the 10 day weather forecast) that although we had to plant heat-loving peppers outdoors, we would cover them to keep them warmer.