Evaluation of the actual resolution of digital aerial and satellite imagery using an edge profile curve

Abstract

The article describes theoretical and practical issues of evaluation of the actual resolution of digital aerial and satellite imagery using an edge profile curve. As a measure of resolution, a linear resolution element, is defined as the minimum width of the image separate linearly extended object is still detectable in the image. The edge for the purposes of estimation a digital image is defined. The theoretical part of the article is devoted to the description of the method for estimating the resolution of an image using an edge profile curve and a fast Fourier transform. An algorithm for automatically estimating the resolution of digital photo images along an edge profile curve is presented. Terms of selection of an edge in a digital image area are defined and an algorithm for automatically finding edges in the image that meet the specified conditions in the best way is developed. A method for automatically extracting edge profile curve from a digital image is described for the following evaluation of the resolution. A method and algorithm for the transition from pixel values of the edge profile curve to the frequency-contrast characteristic of a digital image is described. The results of an experimental accuracy estimation of determining the resolution with the method using the proposed algorithm are compared with the results obtained visually by the resolution test chart. The examples of the results of evaluation of the actual resolution for various aerial and satellite imagery are presented.