The Equal Area Level method for contour maps in Surfer will automatically calculate contour levels so that there are an equal number of grid nodes (equal map area) within each contour interval. Choosing this option will ensure that your contour lines are more evenly distributed across flatter topographic areas, rather than being clustered in areas of steep gradient. Let’s take a look at the difference below.
These two maps have the same number of contour intervals. In the Simple contour map, most of the contour lines are clustered around the areas of steepest gradient change – the foothills of Golden, Colorado. Details in the flatter topography to the east are lost. In the Equal Area contour map, contour lines are distributed across the area more evenly, so we can really see those smaller variations in topography towards the east of the map.