Computer Cartography - Module 6 - Isarithmic Mapping

This week's lab module for Computer Cartography 5007L introduced Isarithmic mapping. Isarithmic maps are another type of thematic map that is used to depict continuous and smooth geographic phenomena. There are two types of Israthmic maps, isometric and isopleth. Isometric maps are constructed with true point data in which data values are measured at a point location. Isopleth maps on the other hand are produced using conceptual point data which is collected over an area and presumed to be at point locations. Since Isarithmic maps depict continuous and smooth geographic phenomena throughout a region based on data collected at control points these maps use interpolation which is the process of determining data values for points or areas between those with a known data value.

For our lab, we utilized precipitation data for the State of Washington that was obtained and calculated using the PRISM (Parameter-elevation Relationships on Independent Slopes Model). This interpolation model leverages point data and an underlying grid, such as a Digital Elevation Model (DEM), to generate gridded estimates of monthly or annual precipitation. Our precipitation dataset was generated by applying this method to point data collected from weather monitoring stations and the calculated climate elevation regression for each grid cell within the DEM. The dataset takes into account physiographic factors that may influence climate patterns.

For our first map, we created an average precipitation map for the state of Washington using continuous tones. Our continuous tone map shows a smooth transition for all values and each point is shaded with a hue proportional to the data value at that point. In our second map, we used hypsometric tint by using the Int Spatial Analyst tool and contour lines using the Contour List Spatial Analyst tool. The Hypsometric Tint creates color-scaled areas between the contour lines that enhance the map viewer's ability to visualize a 3D surface. The lighter colors are associated with lower values and the darker colors with higher values. The raster data is separated into bands using a range of values that have upper and lower limits which produces a visual that clearly depicts the changes in data.

Below is my final map utilizing hypsometric tint and contoured overlay.