At the Space Research Centre in Earth Observation Group we have developed an automated image matching method that works integrated ina created stand-alone software. Matching points at reference and input image are marked automatically. To this end, edge detection is performed on the image using Canny’s algorithm. After this, straight lines are identified and on the intersection pointsbetween these lines, characteristic image points are created. From these points both images will selectcorresponding pairs of points to be matched. The points selected for this task must fulfill threeconditions. Firstly, maximal and minimal distance between the points must be kept within the defined threshold values. Secondly, the angle between intersected segments that define a matching point mustbe similar. And at lastly, the correlation coefficient indicating pixel value defined at the surroundingpoint zone must be the same, allowing a predetermined margin over the defined threshold value. Using the matching points obtained during this process, the parameters of the transformation matrix are obtained, being those parameters the base for geometric image correction.The purposed method is characterized by high accuracy of its results. The firsts tests were performed using Matlab development environment and then, taking in mind the increasing need of high speed performance, the algorithm was adapted to work using CC++ libraries. Based on this algorithm, we have developed and implemented the software application matSIM. We have released this application under afreeware license.The user friendly graphic interface improves the usability and facilitates image visualization and selection of used regions ofinterest where matching points will be searched. Additionally, the application allows changing defaultparameters such as transformation method used(lineal, bilinear, quadratic) and resampling type(nearest neighbor, bilinear).The input and output dataformat is GeoTIFF.
Full article (in Polish).