DESIGN OF AN AIRBORNE INTERFEROMETRIC SAR FOR HIGH PRECISION DEM GENERATION 
  
  
Joáo Moreira 
Aero-Sensing Radarsysteme GmbH fs 
c/o DLR Research Centre — 
82230 Oberpfaffenhofen, Germany FE 
S 
IR 
FT 
KEY WORDS: SAR, Interferometry, DEM/DTM, Mapping, Orthoimage, Processing E 
T 
ABSTRACT: 
This paper describes the Interferometric SAR (InSAR) of Aero-Sensing, AeS-1. The system AeS-1, being designed and 
manufactured at Aero-Sensing, will be mainly used for generation of fully geocoded SAR images and Digital Elevation D 
Models (DEM). AeS-1 has a maximal ground resolution of 0.5 m x 0.5 m and a height accuracy of 0.5 m. AeS-1 will have ol 
the first tests in August 1996 and will be operational in November 1996. The expected products of the AeS-1-System are S 
presented. Finaly, the results of the DLR SAR, E-SAR, are shown. 
e 
1. INTRODUCTION The preliminary estimation of the height accuracy 
measurement is around 0.5 m. The navigation system 
Aero-Sensing Radarsysteme GmbH is engaged in the used for SAR motion compensation is composed by a ° 
field of microwave remote sensing by making use of strap-down inertial system, a differential on-line GPS, fo 
Synthetic Aperture Radar (SAR) systems on both air- D-GPS, and a radar altimeter. The Flight Control 
and spaceborn platforms. It is a private enterprise System of IGI, Aero-Control, processes the data of the 0. 
founded in early 1996 by former scientists of the navigation units by using Kalman filter techniques and 
German Aerospace Research Establishment (DLR), delivers the aircraft motion to the interferometric 2 
who were involved in the design and construction of the processor. 
E-SAR, the Experimental Airborne SAR-System of DLR. ec 
Table 1 shows the main imaging configurations of the : 
AeS-1-System. The ground and radiometric resolutions lai 
2. THE INTERFEROMETRIC SAR can be set to the following values: 
e 0.5 x 0.5 m with 4 looks e 
The Interferometric SAR (InSAR) of Aero-Sensing, AeS- e 1.0 x 1.0 m with 8 looks and to 
1, being designed and manufactured at Aero-Sensing, e2.0x 2.0 m with 16 looks. ar 
will be mainly used for generation of fully geocoded ar 
SAR images and Digital Elevation Models (DEM). The The throughput of the processing chain was calculated Sp 
instrument is installed on board a DLR Cessna 207 considering a SGI-Computer with 8 processors and 2 
aircraft, which is a small aircraft, offering the advantage Gbyte RAM. e 
of low costs. The radar will have the first tests in August flo 
1996 and will be operational in November 1996. It 3. THE INTERFEROMETRIC PROCESSOR frc 
operates in the interferometric mode as following: an 
The interferometric processor consists on the SAR en 
* operating frequency: 9.6 GHz processing, interferometric and geocoding chain. The de 
e baseline: 1.5 m (orthogonal to line of sight direction) SAR processing chain has full motion compensation 
e system bandwidth: 400 MHz capability. The interferometric chain uses a new ° 
e ground resolution: up to 0.5 mx 0.5 m approach for phase unwrapping (Fornaro et al.,1996). A otl 
e swathwidth: 1 to 14.8 km fusion procedure of strong-filtered and less-filtered his 
e flight velocity: 60 - 120 m/s unwrapped phases using Kalman filter technique is 
e flight altitude over NN: 1000 to 3500 m used (Lanari et al., 1996). These algorithms allow the ° 
full automation of the DEM generation process, making We 
In general, the radar allows an aircraft velocity range the SAR interferometry an attractive tool for topographic 
between 50 and 200 m/s and a flight altitude range of purposes. Due to the absolute position accuracy given ° 
100 to 10.000 m over ground. by the D-GPS, the transformation „phase to height“ and he 
geocoding become straight forward procedures. 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996