ABSTRACT
Positional accuracy refers to the spatial agreement of an object displayed on an image as compared to the actual position of that object on the ground (true position). The true ground position points or coordinates are often referred to as reference data. This reference data typically consists of GPS- controlled, field-collected locational points. Determining how far the corresponding locations on an image are away from the measured or known position (geodetic and other geo-referenced) of a given point on the surface of the Earth is known represents the positional accuracy. This exercise will determine the positional accuracy of an image using a simple worksheet to calculate the Average Euclidean Distance (the straight-line distance) and the Root Mean Square Error (RMSE) values.
