Synthetic aperture radar (SAR) geometric invariants

This research develops a new theory of Synthetic Aperture Radar (SAR) geometric invariants (GIs) and demonstrates the existence of SAR GI features in both synthetic and measured SAR imagery. Several previously unknown invariant configurations are derived. The fundamental radar invariant consists of three collinear scattering centers (SCs) and is termed the Collinear Scattering Center Invariant (CLSCI). The CLSCI is a GI configuration under the conventional one-dimensional radar sensor transformation, and as a consequence it is also a SAR GI. Using the CLSCI it is shown that four coplanar SCs also form a new SAR GI termed the Co-Planar Scattering Center Invariant (CPSCI). The CPSCI is validated using measured SAR imagery in several image registration experiments. As an alternate approach, the fundamental SAR object-image relation (OIR) is derived. This OIR is validated using synthetic imagery in combination with both CAD-based and physical object-based 3-D SC measurements. By directly relating 3-D and 2-D scattering center geometry without any knowledge of the sensor transformation, this new OIR holds the promise of fundamentally changing the way in which future SAR model-based image recognition is performed.