It's wrong by about 5%, you can see it if you just try to do it by hand or eye (mentally rotate that red line about the NW endpoint and it should sweep all of p

It's wrong by about 5%, you can see it if you just try to do it by hand or eye (mentally rotate that red line about the NW endpoint and it should sweep all of poland.) https://imgur.com/a/NEwNxVl https://imgur.com/a/NEwNxVl Circle: https://i.imgur.com/omKqty4.png https://i.imgur.com/omKqty4.png I don't think it's a latitude/distance vs Pythagoras thing because the two SE points are only about 1.25 degrees apart - you'd expect about 1 part in 72 difference. (You can get a lot of useful work done with Pythagoras and a lat/long if you assume that the equator to pole gore is a triangle rather than curved - linear variance rather than with the cosine, it works well wherever there are people/paid gis work.)