Rectification

Geometric rectification is the process of correcting geometric distortions in imagery and assigning geographic coordinates to the image by the use of ground control points. Features that are clearly visible on both the image and map (road intersections, airport runways) are given ground control points in image to map registration. The more control points used the more accurate the results. Errors in rectification can come when discernable features are not available or there is a mistake in intrepretation of the features.