Combining multiple images is difficult due to the perspective of the shot and lens distortion. A process called orthorectification must be carried out to to generate an image with a constant scale. Removing the image distortions allows us to generate an accurate map where features are shown in their true position.
An example of orthorectification is shown below. Each image must be adjusted and tilted to produce an accurate map.
A recent survey we conducted of Bandon, co. Cork shows the power of this technique. A 170 megapixel photomosaic of the river Bandon was generated from just 50 images.