Method for providing position determination assisting data in a cellular communications network, comprising the steps of: establishing a cell relation configuration for a user equipment, said cell relation configuration comprising at least cell identities of cells, in which signals (25,26) to/from said user equipment fulfil at least a specific radio condition criterion when received; performing a high-precision position determination for said user equipment; repeating said establishing and performing steps (204,206) a plurality of times; clustering points being results of said high-precision position determinations belonging to the same cell relation configuration in separate result clusters; associating a polygon with at least one of said result clusters, said associating step in turn comprises the steps of: encompassing a first result cluster of said result clusters by a polygon; altering the position of corners of said polygon along defined paths (61,97) being curves through the original corner position and a single point to improve a predetermined criterion while maintaining at least a predetermined percentage of said results of high-precision position determinations of said first result cluster within the polygon; and counteracting corners of said polygon from gathering at a minor portion of a circumference of said polygon; creating position determination assisting data comprising a relation between said cell relation configurations and said polygon. establishing a cell relation configuration for a user equipment, said cell relation configuration comprising at least cell identities of cells, in which signals (25,26) to/from said user equipment fulfil at least a specific radio condition criterion when received; performing a high-precision position determination for said user equipment; repeating said establishing and performing steps (204,206) a plurality of times; clustering points being results of said high-precision position determinations belonging to the same cell relation configuration in separate result clusters; associating a polygon with at least one of said result clusters, said associating step in turn comprises the steps of: encompassing a first result cluster of said result clusters by a polygon; altering the position of corners of said polygon along defined paths (61,97) being curves through the original corner position and a single point to improve a predetermined criterion while maintaining at least a predetermined percentage of said results of high-precision position determinations of said first result cluster within the polygon; and counteracting corners of said polygon from gathering at a minor portion of a circumference of said polygon; encompassing a first result cluster of said result clusters by a polygon; altering the position of corners of said polygon along defined paths (61,97) being curves through the original corner position and a single point to improve a predetermined criterion while maintaining at least a predetermined percentage of said results of high-precision position determinations of said first result cluster within the polygon; and counteracting corners of said polygon from gathering at a minor portion of a circumference of said polygon; creating position determination assisting data comprising a relation between said cell relation configurations and said polygon.