This map depicts the average rainfall values for the state of Washington from 1981-2010. This is an isarithmic map displaying the precipitation values in interval ranges which are subsequently color coded. The data was created by a PRISM (Parameter-elevation Regression Slopes Model) mapping system. This is an algorithm that interpolates precipitation data in conjunction with a digital elevation model (DEM) to correct the interpolated values by representing the influence elevation has on precipitation.
In this lab, we were tasked with taking the PRISM data and first displaying in continuous tones. This was accomplished by uploading our data into ArcGIS Pro. Continuous tone maps ascribe a color value to each pixel which subsequently represents a data value. In order to observe the relationship between precipitation and elevation, we took the elevation values embedded within the PRISM data, and created a hillshade effect. This presented us with a three dimensional elevation layer showing the topography of Washington. Below is the continuous tones and hillshade map.
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It is apparent that there is a relationship between elevation and precipitation volume. In addition, you can see the relatively arid regions east of the mountains which is caused by air parcels being forced up by the topography condensing the water vapor in said parcels.
We then took this precipitation data and ran it through the Int spatial analysis tool. Through converting our raster values into integers, we simplified our color display by creating a hypsometric tint. This fills in the ranges between contours with the requisite colors to distinguish intervals. Since we did not yet have established intervals, through the Symbology function, we set them to the appropriate ranges to stay in accordance with our color scheme and ensure each value's contingency to elevation.
In order to make our hypsometric tint easier to read, contours were added through the contour function. A brief description was then added and the appropriate map elements were positioned on the final product.
Contouring, hypsometric tints, and continuous color tone maps are incredibly valuable methods to display data. There are used for data that, though stratified, is distributed in value across the entire region of the map. Continuous tones allow for heightened efficacy in detailed communication where contours and hypsometric tints tend to generalize the information to represent data clusters.
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