Isarithmic Mapping

Module 8 introduced the class to Isarithmic mapping. Isarithmic maps depict smooth, continuous phenomena across an area using varying symbology methods. The phenomena are measured at control points and interpolated using the appropriate method. We mapped the state of Washington depicting the annual average precipitation from 1981-2010. The precipitation data was derived by measuring at control points and interpolated using PRISM (Parameter-elevation Relationships on Independent Slopes Model). This interpolation method accounts for major physiological factors (location, elevation, coastal proximity, topographic orientation, vertical atmospheric layer, topographic position, and orthographic effectiveness of the terrain) influencing climate patterns. As precipitation generally increases with elevation, PRISM integrates elevation into the surface by utilizing a digital elevation model (DEM). I created two maps with one using continuous tone symbology and the other using hypsometric tinting. The first map is a continuous tone map showing the annual average rainfall in Washington state from 1981-2010 using smooth stretch symbology. The second map implements hypsometric tinting and utilized classified symbology with the data manually divided into 10 different classes. Relief was incorporated into both maps by employing the hillshade effect but the hypsometric tint map also shows contour lines. The hypsometric tint map was ultimately used for the end product because it is ideal for geographically smaller areas such as a state where the continuous tone map would have been more appropriate if the map was of the United States.