The imaging results obtained from two helicopter flights in the vicinity of Oberpfaffenhofen will be summarised below. The first scene contained a large corner reflector as the main scattering element and data from this recording were used to calibrate the system. The second raw data set was obtained during a flight across the river ?Lech?.
Corner Reflector Response
In order to demonstrate that the focusing is both time- and space invariant, a sequence of 10.000 image frames corresponding to a flight period of 37,9 seconds has been processed. A visualisation of the azimuth profiles of the corner reflector responses is shown in the figure below as a 3-D surface plot. It becomes evident, that the focusing remains stable over the investigated time interval and that azimuth and elevation independent raw data compression has been achieved.
Imaging Results from a Natural Scene
In order to test the functional SIREV model in a realistic application scenario radar raw data were collected during a flight across the river Lech. The data were stored on a hard disk array and processed offline. An example of the processing results obtained from this raw data set is shown in the figure below. The image on the left shows the focused image obtained from a single raw data frame. It is evident that this image suffers from a contamination with noise. By combining several successive image frames in a coherent averaging process the image quality may be substantially improved (right). Such a phase preserving image enhancement technique requires the computation of an average phase offset which is shown in the middle column of the figure. This smoothed interferogram may also be further processed to supply additional information about the topography and obstacles in the field of view.