Many propagation prediction algorithms for the VHF and UHF ranges of Radiocommunication Study Group 3 are terrain-based. That is, they rely on terrain data as one of the bases of their calculations. Generally speaking, there are two kinds of terrain data applicable to radio propagation calculations: hypsographic and morphologic. Hypsographic data describes the elevation characteristics of the terrain being described; i.e. terrain height. Morphologic data describes the ground cover characteristics.