High-Precision Geolocation Of Airborne SAR Data With Few (None) Ground Control Points

Synthetic Aperture Radar (SAR) Technology, characterized by its all-time, all-weather and penetrable capability, has been a primary technical means in data acquisition and mapping within the difficulty area at present. Airborne SAR system owns couple of features such as real-time acquisition, real-time processing, and flexibility; it can produce large-scale, high-resolution, and high-accuracy SAR data on the demand of users. Now it has been paid more and more attention by researchers all over the world. Therefore research on precise geolocation of airborne SAR images has been an important field in SAR data processing technologies.The traditional way of airborne SAR image positioning is employing Ground Control Points (GCPs) as many as possible, and topographic mapping in large area with few GCPs still has heavy disparity, meanwhile airborne SAR mapping with few or none GCPs is a burning question. According to the analyse on geometric characters of airborne SAR images, the main research topics of this dissertation are airborne SAR error sources and their effects, block adjustment of airborne SAR under the circumstance of few GCPs, direct positioning model of airborne SAR images with none GCP, high accuracy of SAR image positioning in extremely conditions like complex topography, large-scale, and few or no GCPs, raise in mapping effective and accuracy in difficulty area.The main research contents and contributions are as follows:1. Airborne SAR positioning models are analyzed. According to geometric characteristics and distortions of SAR images, the difference between SAR and optical images, the variances between airborne and spaceborne SAR are analyzed respectively. The principles and processing flows of airborne SAR positioning are studied. Airborne SAR positioning models are described emphatically. The availability, merits and demerits of every SAR positioning model are analyzed and compared.2. The key technical indexes of Airborne Multi-band Multi-polarization SAR Interferometry (InSAR) Mapping System are designed. Factors that restricted the accuracy of interferometry are studied and errors propagation by them is reasoned, the baseline length of X-band InSAR System is designed, which provides aircraft modification with technical foundation.3. Airborne SAR airline solution for complex terrain is studied. Reasons and factors of the shadow are analyzed spe cifically. Methods of eliminating shadow are proposed:increasing overlap ratio of SAR images, imaging from two directions and imaging on vertical direction. The effect of these methods in eliminating shadow are analyzed quantitatively. The reasons caused shadow by various terrains and possible eliminating methods are analyzed in Hengduan Mountain Region, and airborne SAR flight lines are designed in this area.4. A block adjustment model with few GCPs for airborne SAR is proposed. The model uses multi-photo united adjustment algorithm based on polynomial model with height displacement correction and F. Leberl imaging model. It is available for multi-scene SAR images with different looking side, flight height, resolution. According to multi-photo united adjustment model, software has been programmed. Additionally, experiments and improvement models have been done. The experimental results verified the 1:10000 scale topographic mapping block adjustment in plain and hilly terrain area.5. A direct positioning model with none GCP is put forward. Position and Orientation System (POS) data processing method is studied, including radar antenna dynamic eccentric correction and antenna phase center interpolation. Airborne SAR high-accuracy positioning method with none GCP is proposed which is based on high accuracy position and attitude data produced by POS. The model can satisfy 1:50000 scale topographic mapping through the experiment.6. The airborne SAR multi-strip block united geocoding model with few GCPs is brought up. The airborne SAR multi-strip block united geocoding algorithm is studied, including coarse positioning of single flight strip, airborne SAR multi-strip block adjustment and fine positioning of single flight strip. The GCPs layout plan of airborne SAR multi-strip block is brought forward as well.