Hello there,
I have a problem with complex geometries and the Union command.
Background: I have parcel Feature Classes and am calculating the coverage of construction polygons from several Feature Classes. I have to calculate those coverages and coverage combinations in a very precise way as the information will be used to elaborate lease agreements.
Method and problem. I use a parcel Feature Class and several construction Feature Classes. As I also need all possible combinations of constructions per parcel, I use the Union Geoprocessing tool (ArcGIS Pro 3.3) in order to combine all input layers. All Feature Classes are calculated into one result Feature Class which includes all intersecting geometries. Afterwards I use a Python script to quantify all coverages/coverage combinations and write those values in the parcel Feature Class. In general, the whole process does function pretty well. My problems start, when I use complex geometries (circles, ellipses in Geodatabases). When I have a circle and another feature without their borders intersecting, all is fine! The input and result Hape Areas of the circles are the same. If the circles boundary is intersected by the boundary of one of the other feature, it will be split (which is to expected). If I take the result areas, which belong to the circle from the union result, the combined Shape Area will not be the same as the input Shape Area (of course taking into account that all files have the same coordinate system, etc.).
ArcGIS Pro trys to use complex geometries (arcs) to reconstruct the geometry of the input circle but fails to match it completely. The only way I found to reduce this problem is to use higher precisions for the Resolution (0,00000001 meters) and Tolerance (0,00000003 meters) in the environmental settings. But still, I get roughly a 2 square centimeter error with a circle which has a radius of 40 meters.
Here some example values:
- Input circle: 1317.227075 m²
- Combined Union result areas of this circle (without modifying env-settings): 1317,197206 m²
- Combined Union result areas of this circle (with modifying env-settings): 1317,201008 m²
Is there a way to get more precise or even perfect results?
I have included an attchement with a set of demo data (parcels, construction 1 & construction 2).
I appreciate any help in this matter and thank you in advance for ideas and recommendations.
Beste regards
Lars
