The urban purple line refers to the boundaries of the protection scope of historical and cultural blocks announced by the national historical and cultural cities and the people's governments of provinces, autonomous regions and municipalities directly under the Central Government, as well as the people's governments at or above the county level outside the historical and cultural blocks.

"Building control line" refers to the boundary that the location of the building base cannot exceed after a certain distance from the red line, road red line, green line, blue line, purple line and yellow line. Concession distance and various control and management regulations shall be implemented in accordance with the provisions of the local planning department.