GIScience
Area calculation inconsistencies
When calculating the area in square meters https://github.com/GIScience/openpoiservice/blob/75791a20e8da7fb321789f9cdf3e196713781993/openpoiservice/server/api/views.py#L251 the resulting area is sometimes a lot (up to double) bigger than the "real" area. "Real" area can either mean https://github.com/scisco/area implementation of geojson-area and/or Wikipedia for a given administrative boundary.
Example: Take the administrative boundary of Luzern, CH (https://nominatim.openstreetmap.org/ui/details.html?osmtype=R&osmid=1682891&class=boundary). Wikipedia states 29 square kilometers. The area package (as well as geojson.io) calculates somewhere around 31 square kilometers. openpoiservice, however, calculates 67 square kilometers.
This is to be expected using 3857... please feel free to raise a PR using a more suitable projection.
