Projected Coordinate Systems and Distance Analysis

Fig. 1: Closest National Park/Preserve Locator for the contiguous United States. This map shows the closest National Park at any point within the contiguous U.S. When measuring distance, it is important to use a distance-preserving coordinate system. In this case, “USA Contiguous Equidistant Conic” was chosen for its distance-preserving properties.

Fig. 2: Protected Area Land percentage per country displayed with the Mercator projection. Because the Mercator makes southern and northern regions appear much larger, it seems as though countries to the north have less protected land than they actually do. This is why area should not be measured using the Mercator projection.

Fig. 3: Protected area land percentage per country displayed with the Equal Earth projection. Unlike the Mercator projection, Equal Earth preserves area. As a result, northern and southern countries appear to have higher protected land percentages. 

Fig. 4: Model for creating the Thiessen polygons shown on Figure 9. The model takes three inputs; national parks, states, and a population raster. All respective datasets are projected into the desired coordinate system (“USA Contiguous Equidistant Conic”), clipped to the contiguous United States, and then Thiessen polygons were constructed and “zonal statistics” was used to generate the “population per zone” field shown in Figure 10.