FAQ: What algorithm is used by ArcGIS for Desktop to determine the area of a polygon?
What algorithm is used by ArcGIS for Desktop to determine the area of a polygon?
The algorithm used in ArcGIS to calculate the area of a polygon is called 'Area Calculation by Gauss'. Esri uses a normalized form of it to preserve numeric precision. This is a common algorithm.
The algorithm calculates the area for each ring (part) in a polygon. If the ring is clockwise (outer ring) the area is positive, and if the ring is counterclockwise (inner ring) the value will be negative.
A partial sum of a trapezoid's area is used where:
partialSums - Array of double cPoints - Number of points in the ring points - Array of point structure, the structure as X and Y as attributes yOrigin - Double equal to the Y value of the last point (cpoints-1)