Responsive to receiving an indication of a geographical area, one or more constituent areas associated with the geographical area are identified. Boundary data corresponding to the constituent areas is accessed. The boundary data for each constituent area comprises a plurality of geographical location points defining line segments that define the boundary of the corresponding constituent area. Unique portions of line segments are identified. A unique portion of a line segment is a portion of a line segment defined in the boundary data of one and only one of the constituent areas. The geographical area boundary layer is defined. The geographical boundary layer comprises a set of line segments consisting of the unique portions of line segments. A geographical map is provided for display via a user interface. The geographical map comprises a plurality of layers. The plurality of layers comprise one or more map layer sand the geographical area boundary layer.