Based on two radar images supplied by SRTM (one of the two images can be seen on the extreme left of this illustration), the first intermediate step is to calculate the differences between them. These differences in phase information are then depicted in the second image from the left as fringes. From these, the elevation model (third image) can be derived. Low-lying regions are shown as dark areas, with lighter coloured areas denoting higher elevations. Each grey-scale value represents an elevation measured in metres above sea level. The last image in the sequence shows the final digital elevation model, shaded and coloured using an atlas colour scheme. To make the image easier to interpret, the radar image is incorporated into the colour data.