Annual Precipitation in Idaho

Figure 1. The distribution of annual precipitation in Idaho. The isohyets and underlying raster layer were interpolated from weather station data using the Inverse Distance Weighting (IDW) method. The optimal IDW “k” value (3.191) was computed using the ArcGIS cross validation tool. Although the precipitation raster could have been classified and displayed as a choropleth map, more localized variation and relative differences between other interpolation methods can be observed when using a full-spectrum color ramp. In addition, homogeneous precipitation regions are difficult to discern when using a single-hue color ramp, further justifying the multi-hue color scheme.




Figure 2. The distribution of annual precipitation in Idaho. The isohyets and underlying raster layer were interpolated from weather station data using the Kriging interpolation method. The Kriging operation was performed using a lag size of 38,884 and lag number of 12, yielding an RMSE of 3.523 with an exponential mathematical model. Although the precipitation raster could have been classified and displayed as a choropleth map, more localized variation and relative differences between other interpolation methods can be observed when using a full spectrum color ramp. In addition, homogeneous precipitation regions are difficult to discern when using a single-hue color ramp, further justifying the multi-hue color scheme.