centroid_or_mid - ObjectVision/GeoDMS GitHub Wiki

Geometric functions centroid_or_mid

• centroid_or_mid(polygon_data_item)

centroid_or_mid(polygon_data_item) results in a point data item with

1. the centroid if it is located in the polygon
2. or else the mid of the polygon_dataitem argument. The mid of a polygon is calculated as the middle point of the coordinates of the polygon in such a way that it is always located within the polygon. See here for a description.

The centroid_or_mid function results in the centroid if it is located within the polygon or else in the mid of the polygon. This means the result of the centroid_or_mid is always located within the polygon, or at its border such that point_in_polygon would return true.

In the image above the centroid is not located within the polygon. The centroid_or_mid function will still result in a point within the polygon.

data item polygon_dataitem with fpoint or dpoint value type and composition type polygon.

attribute<point_rd> centroid_or_mid (district) := centroid_or_mid(district/geometry);

domain district, nr of rows = 3

• centroid
• mid