53 Pa.C.S. § 720: Monuments.

The impacted municipalities shall provide for the placement of monuments, no more than 1,500 feet apart, along the newly established boundary line, other than where a natural line can be described, in a manner adequate that the entire territory in question can be depicted and represented for the future. The coordinates of monuments shall be expressed in terms of the State Plane Coordinate System in effect on the date of the change of boundary.