Perpendicular bisector construction of a quadrilateral
In geometry, the perpendicular bisector construction of a quadrilateral is a construction which produces a new quadrilateral from a given quadrilateral using the perpendicular bisectors to the sides of the former quadrilateral. This construction arises naturally in an attempt to find a replacement for the circumcenter of a quadrilateral in the case that is non-cyclic.
Source: Wikipedia — Perpendicular bisector construction of a quadrilateral (CC BY-SA 4.0)