Accuracy prediction for ortho-image generation

Abstract

This paper revisits the basic mathematical formulation of ortho-image (digital orthophoto) generation. The main objective is to provide an approach for predicting the accuracy of an ortho-image, according to the accuracy of the digital elevation model (DEM), control points and image measurements, the configuration of fiducial, tie and control points, and the ground slope. The approach is based on applying the well-known law of error propagation to the mathematical model of ortho-image generation. Although it may seem intuitive for professionals in the field of photogrammetry, such an approach is essential in the era when specialists in other fields use off-the-shelf software packages for ortho-image generation. Simulations with the derived approach show that the accuracy of the ortho-image is more sensitive to errors in image measurement of fiducial, tie and control points and ground coordinates of control points, than to DEM errors. Non-standard configurations of fiducial, tie and control points further impair the accuracy. In addition, certain combinations of point location and ground slope might lead to unacceptably large error on the ortho-image.