The effect of positional precision of control points on the quality of geometric correction of high spatial resolution satellite images

Abstract

In order to produce grand scale topographic maps, the new generation of sensors provides us with high- spatial resolution images. However, before using these images, they must be geometrically corrected, a process that is affected by errors, some of which are related to the nature of the original data (images), and others resulting from the processing process. The last type of error is due to algorithms for correcting geometric distortions as well as to external data (control points) needed by correction process and resampling algorithms.

This study aims is to analyze the effect of spatial accuracy of the control points on the images geometric correction accuracy, and this is done by applying tests on the same image (IKONOS), where polynomial transformations were applied using sets of control points, each with absolute accuracy different from the other. These points were extrapolated from a 1/1000 topographic map and from a georeferenced MOMS satellite image with geometric accuracy of 2m and measured by GPS. The study showed that it is possible to obtain the most accurate geometric correction by using control points with absolute accuracy close to the spatial resolution of the image. It also showed that the use of more precise control points would not ameliorate the accuracy of the geometric correction, because the measurement of these points on the image is limited by its spatial resolution.