A pipeline for automated processing of declassified Corona KH-4 (1962–1972) stereo imagery

Ewelina Rupnik

Abstract:

The Corona KH-4 reconnaissance satellite missions from 1962-1972 acquired panoramic stereo
imagery with high spatial resolution of 1.8-7.5 m. The potential of 800,000+ declassified Corona
images has not been leveraged due to the complexities arising from handling of panoramic imaging
geometry, film distortions and limited availability of the metadata required for georeferencing of
the Corona imagery. This paper presents Corona Stereo Pipeline (CoSP): A pipeline for processing
of Corona KH-4 stereo panoramic imagery. CoSP utlizes a deep learning based feature matcher
SuperGlue to automatically match features point between Corona KH-4 images and recent satellite
imagery to generate Ground Control Points (GCPs). To model the imaging geometry and the scanning
motion of the panoramic KH-4 cameras, a rigorous camera model consisting of modified collinearity
equations with time dependent exterior orientation parameters is employed. The results show that
using the entire frame of the Corona image, bundle adjustment using well-distributed GCPs results
in an average standard deviation (SD) or σ0 of less than 2 pixels. We evaluate fiducial marks on
the Corona films and show that pre-processing the Corona images to compensate for film bending
improves the accuracy. We further assess a polynomial epipolar resampling method for rectification
of Corona stereo images. The distortion pattern of image residuals of GCPs and y-parallax in epipolar
resampled images suggest that film distortions due to long term storage as likely cause of systematic
deviations. Compared to the SRTM DEM, the Corona DEM computed using CoSP achieved a
Normalized Median Absolute Deviation (NMAD) of elevation differences of ≈ 4 m over an area of
approx. 4000 km2. We show that the proposed pipeline can be applied to sequence of complex scenes
involving high relief and glacierized terrain and that the resulting DEMs can be used to compute long
term glacier elevation changes over large areas