Line Image Shift Correction for Airborne Scanning Sensors
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Solution Overview
Problem
Existing scanning sensors on vehicles flying over celestial bodies face challenges in correcting shifts in line images due to high-frequency vibrations, which result in geometric deformations in composite images, as existing methods require at least two images showing the same scene portion and cannot handle shifts in composite images formed from different scene portions.
Innovation Solution
A method to estimate and correct shifts in line images using a local model of similarity variation, calculating relative lateral and longitudinal shifts by maximizing similarity values, and integrating these shifts to form corrected composite images, even when line images show different portions of the scene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated sensors (gyroscopes) are used to estimate low-frequency vibrations during acquisition, then low-frequency shifts can be corrected, but high-frequency vibrations caused by local sensor vibrations cannot be detected
Solution Approach 1:
The patent uses the observed scene itself as an intermediary reference to detect high-frequency vibrations. By comparing the positions of homologous characteristic areas in successive line images, the method indirectly measures sensor vibrations without requiring dedicated high-frequency sensors. This mediator approach allows detection of vibrations across the full frequency spectrum including high-frequency local vibrations that dedicated sensors cannot capture.
2Measurement precision
If homologous characteristic areas are matched in two images showing the same scene portion to reconstitute line of sight, then line of sight can be determined, but this method cannot be applied to composite images formed from different scene portions
Solution Approach 1:
The patent extends the homologous area matching method to work universally for both individual images and composite images. By identifying characteristic areas that appear in multiple line images within the composite image and matching their positions, the method determines relative shifts for each line image. This universal approach allows the same technique to correct shifts in composite images formed from different scene portions, overcoming the limitation of traditional methods.
3Productivity
If line images are simply juxtaposed to form composite images, then image formation is straightforward, but geometric deformations occur due to uncorrected shifts from high-frequency vibrations
Solution Approach 1:
The patent performs preliminary detection and correction of line image shifts before final composite image formation. By calculating the positions of homologous characteristic areas in each line image and determining relative shifts, the method pre-corrects the line images for geometric deformations. This preliminary action ensures that when line images are juxtaposed to form the composite image, the geometric accuracy is maintained while preserving efficient image formation.
Data Source
AI summary
Method for estimating shifts of line images obtained by an airborne or spaceborne scanning sensor. The invention relates to a method for estimating shifts in line images of an image, referred to as a “composite image”, made up of the juxtaposition of J line images. The line images show portions of a scene on the surface (S) of a celestial body that are different and successively acquired by a row of sensitive cells of a sensor (10) on board a vehicle flying over the celestial body. The shifts in the line images are induced by sighting errors of the sensor (10) during the acquisition of the line image Lj. The lateral and/or longitudinal shift of a line image Lj relative to a line image Li, where j is different from i, is estimated according to a local model of lateral and/or longitudinal variation of the similarity between different line images.