Aircraft Geolocation Using Passive Optronic Sensor Overlap
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Solution Overview
Problem
Existing geolocation methods using passive optronic sensors on aircraft suffer from significant errors in determining the x-coordinate of stationary targets, especially at grazing angles and when the difference in height between the target and the aircraft is unknown, leading to inaccuracies due to errors in roll angle measurements and atmospheric refraction.
Innovation Solution
A method involving the acquisition and overlap analysis of images from different aircraft positions to calculate the distance between the target and a known point, using angles and pixel coordinates to determine the x-coordinate independently of height and refractive effects, thereby reducing errors and improving precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the x-coordinate is calculated using the formula X=h·tan R with single image data, then the calculation is simple, but the geolocation precision deteriorates significantly at grazing angles and when height differences are unknown
Solution Approach 1:
The patent transitions from using a single image (2D information) to using multiple images taken from different aircraft positions (adding the dimension of time and spatial displacement). This multi-image approach enables triangulation, where the intersection of lines of sight from different positions provides the target location, fundamentally changing the calculation methodology from direct trigonometry to geometric intersection, thereby improving precision without excessive complexity increase
Solution Approach 2:
The patent introduces the aircraft's displacement between two positions as an intermediary element. By knowing the aircraft moved from position C1 to C2 with a measured baseline distance, this displacement serves as a reference that allows calculation of target distance through triangulation, eliminating the need for direct height measurement and reducing sensitivity to roll angle errors
2Measurement precision
If the roll angle measurement precision is increased to reduce geolocation error, then the geolocation precision improves, but the device complexity and measurement difficulty increase significantly
Solution Approach 1:
The patent uses the known baseline distance between aircraft positions as feedback to correct and validate the triangulation calculation. By comparing the calculated target position against the known aircraft displacement, the system can verify measurements and reduce the impact of roll angle errors, achieving acceptable precision without requiring extremely precise roll angle measurements
Solution Approach 2:
The patent changes the measurement parameters from requiring high-precision roll angle (single parameter) to using less precise roll angle measurements combined with the baseline distance and multiple image angles (multiple parameters). This parameter substitution transforms the problem from one sensitive to small angular errors to one where errors are distributed across multiple measurements, reducing the burden on any single measurement
3Reliability
If the area coverage is increased to ensure target area is captured despite geolocation errors, then the target detection reliability improves, but the productivity and time required for reconnaissance deteriorates
Solution Approach 1:
The patent performs preliminary triangulation calculations during the reconnaissance mission itself, using images captured from multiple positions. By calculating target positions in real-time during the mission rather than requiring post-mission processing, the system achieves reliable geolocation without needing to expand the initial survey area, maintaining productivity while ensuring target detection
Data Source
AI summary
The subject of the invention is a method for geolocalization of one or more stationary targets from an aircraft by means of a passive optronic sensor. The sensor acquires at least one image I1 containing the target P from a position C1 of the aircraft and an image I2 containing the target P from a position C2 of the aircraft. The images I1 and I2 have an area of overlap. The overlap area has at least one target P identified which is common to the two images I1 and I2. The position of each target P is determined in each of the two images. The distance d is calculated between each target P and a point C, situated for example in the vicinity of C1 and C2, as a function of the angle β1 between a reference direction and the line of sight of the image I1, the angle β2 between the same reference direction and the line of sight of the image I2, of the position of each target P in the image I1 and in the image I2. The positions of the targets are calculated relative to the projection of the aircraft on the ground when at C, as a function of the distances d in a terrestrial reference frame.