I am working on a project that requires the calculation of the area of a polygon by two different methods. I need to know what algorithm QGIS uses to calculate the area of a polygon. I know ESRI ArcGIS uses the shoelace (Gaussian) method and am looking for GIS software that uses a different method.
QGIS uses the GEOS library for geometry operations:
GEOS uses the shoelace formula:
OGR also uses the shoelace formula: