This picture shows an excerpt from a high-resolution image of the area around the Eiffel Tower. For this interferogram, two images of the same scene, taken from slightly different positions, were superimposed. The resultant coloured rings are an indicator of the relative height of the depicted objects. The variation in colour across the length of the Eiffel Tower enables the precise height of the tower to be established, providing of course that you know the precise position of the satellite at the time the images were captured. These two images were taken on 16 and 27 January 2008 respectively. In the configuration shown here, a complete run through the colour spectrum equates to a height difference of 321 metres, which corresponds precisely to the height of the Eiffel Tower.