1. Select planar surface or datum plane.

2. Establishing datum plane is the base assessing surface parameter.

3. Related to Altitudinal: Altitudinal hemianopia, Altitudinal field defect altitude, vertical distance of an object above some datum plane, such as mean sea level sea level,

4. Angularity: Angularity tolerance symbol is shown as "∠".Angularity tolerance specifies a tolerance zone defined by two parallel plane at the specified angle other than 90 degree from a datum plane or axis within where the surface or the axis of the feature must lie

5. Benchmarks can be divided into two general groups: the "vertical control points" are points that mark a very precise elevation above the standard datum plane (usually referred to as elevation above sea level) and the "horizontal control points" are points with precisely established latitude and longitude.