Extraction, Positioning, and Quality Control of Lamp-Pole GCP From Spaceborne Stereo SAR Images

With advancements in synthetic aperture radar (SAR) imaging geodesy and geodetic stereo SAR, the geometric accuracy of point scatterers (PSs), such as corner reflectors, has reached decimeter or even centimeter levels, making them viable as ground control points (GCPs). Compared with global navigation satellite system (GNSS)-based methods, SAR-based GCP extraction approaches are more efficient and cost-effective. This article investigates the extraction, positioning, and quality control of lamp-pole GCPs from spaceborne stereo SAR imagery. We first reformulate the positioning problem as a Gauss-Markov model (GMM) and derive the relationship between precision and the difference of incidence angles. We then analyze the concept of lamp-pole GCPs, which, due to their visibility in SAR images from multiple orbital perspectives, exhibit high precision. Subsequently, we propose an automatic method for extracting GCPs from stereo SAR images, along with a robust positioning technique that adjusts observations into distance units. Finally, we analyze three quality indicators of the extracted GCPs: precision, internal reliability, and external reliability. We validate the effectiveness of the proposed methods through simulation and real-life Gaofen-3 data.