FAQ: What algorithm is used by ArcGIS to determine a polygon's area?
What algorithm is used by ArcGIS to determine a polygon's area?
The algorithm used by ArcGIS to calculate area is called the shoelace formula or Gauss's area formula. Esri uses a normalized form of this formula to preserve numeric precision.
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 is 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)