Table C.1 lists ASPRS recommendations for the number of checkpoints to be used for vertical and horizontal accuracy testing of elevation data sets and for horizontal accuracy testing of digital orthoimagery and planimetric data sets.
Using metric units, ASPRS recommends 100 static vertical checkpoints for the first 2,500 square kilometer area within the project, which provides a statistically defensible number of samples on which to base a valid vertical accuracy assessment.
For horizontal testing of areas >2500 km2, clients should determine the number of additional horizontal checkpoints, if any, based on criteria such as resolution of imagery and extent of urbanization.
For vertical testing of areas >2,500 km2, add five additional vertical checkpoints for each additional 500 km2 area. Each additional set of five vertical checkpoints for 500 km2 would include three checkpoints for NVA and two for VVA. The recommended number and distribution of NVA and VVA checkpoints may vary depending on the i