Assignment of Features
Metric of Images
Choice of Frame points
The first image 35A72 from the so called 'Face of Mars', which was taken in 1976 by Orbiter 1 or A, was not available in Internet, but in magazins, books and TV. Later on all images were available in imq format on CD, which was at that time common, and these CDs can now be fetched from the Internet.
There are no more data available about the circumstances these fotos were taken, but they can be found in other sources or determined by your own. These original images have been taken from high above over a wide range, so landforms besides the mesa are also visible, from which the coordinates are known roughly, so that it is posible to calculate the resolution of the picture.
Knowing the resolution of the picture, the pixels themselves provide a scale for a map of the landscape. With the number of pixels in x- and -y-direction from a starting point to the end point, it is possible to calculate the distance between them by Pythagors' Theorem. In the following this has not only been done for image 35A72 but for overall 5 images, which allows to determin width and height of the image in a good precision. To avoid deviation from choosing start and end point, the concept of a slide gauge was used with parallel lines in an image edtior software.