Different Area Sizes in SQL Server Databases vs. File Geodatabases

Question

Why do the system fields Shape.Area in SQL Server databases show different area values (m_²) than the Shape fields in file geodatabases?

Problem

The cause of the different area values is arcs (true curves) in the polygons. The largest area differences therefore occur in areas with many arcs.

Solution

When calculating the SHAPE_AREA and SHAPE_LENGTH columns, ArcSDE (which handles geometry storage and processing in enterprise databases) only supports simple features, meaning no arcs but only straight line segments in this case. This results in arcs being approximated by straight line segments for geometry calculation by ArcSDE. This causes the area differences, which vary in size depending on the area and arcs.

Internally, ArcGIS does consider true curves in all calculation and analysis operations, but unfortunately not in the values of the aforementioned fields. Therefore, the value from the geometry calculation in ArcMap is the correct one, not the values in the SHAPE fields.

Esri treats this behavior not as a bug, but rather as a known issue or "works as designed."

Furthermore, this means that for area calculations, these system fields must not be used, but rather the Esri functions "calculate geometry" or the GEONIS parser function %AreaPrec.

Esri Articles

https://support.esri.com/de/bugs/nimbus/QlVHLTAwMDEwOTEzMA==
https://support.esri.com/de/bugs/nimbus/QlVHLTAwMDA5NzMzMg==
https://support.esri.com/de/bugs/nimbus/TklNMDQ1NjUz