We have one more calculation before we move on to editing GIS data. The most basic unit of GIS is a point. Two points can form a line. Multiple lines that share endpoints can form a polyline, and polylines can form polygons. Polygons are used to represent everything from a house to an entire country in geospatial operations.
Calculating the area of a polygon is one of the most useful operations in GIS if we wish to understand the relative size of features. But in GIS, area calculations go beyond basic geometry. The polygon lies on the Earth, which is a curved surface. The polygon must be projected to account for that curvature.
Fortunately, there is a pure Python module simply called area that handles these complications for us. And because it's pure Python, you can look at the source code to see how it works. The area module's area...