Scene Correlation North Reference for Inertial Measurement Units
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Solution Overview
Problem
Conventional inertial measuring units (IMUs) in man portable targeting systems face challenges in accurately maintaining a north reference due to weight, power consumption, and accuracy issues, making it difficult to achieve milliradian accuracy for targeting, especially in field conditions where manual correction is required and celestial navigation is unreliable.
Innovation Solution
A scene correlation-based system that uses a reference image with identifiable characteristics to calculate a directional vector, allowing an IMU to automatically correct its north reference by matching target images with the reference image, eliminating the need for manual skill and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inertial measuring units (IMUs) are used for north reference, then targeting accuracy can be achieved, but the system becomes too heavy and consumes too much power for man portable use
Solution Approach 1:
The patent replaces the mechanical inertial reference device (north finding gyroscope/compass) with an optical/electronic scene correlation system. The system uses a camera to capture images and correlates them with reference images to automatically determine north reference, eliminating the need for heavy mechanical gyroscopes while maintaining milliradian accuracy for targeting.
Solution Approach 2:
The patent uses image copying and correlation techniques where a captured scene image is correlated with a reference image that has a known north reference. By matching identifiable characteristics between the two images, the system determines the rotational offset and establishes north reference without physical inertial sensors.
2Measurement precision
If north finding gyroscopes are used, then accurate north reference can be obtained, but the device becomes bulky and requires excessive power
Solution Approach 1:
The patent replaces power-consuming mechanical north finding gyroscopes with an electronic image correlation system. The system processes images through correlation algorithms to determine north reference, consuming significantly less power while achieving the same milliradian accuracy required for precision targeting.
Solution Approach 2:
The scene correlation system uses the environment itself (visible features in the captured image) to establish north reference, rather than requiring external power-intensive inertial sensors. The system serves itself by using readily available visual information from the battlefield environment to determine orientation.
3Weight of moving object
If magnetic compasses are used for north reference, then the system remains lightweight, but the north keeping capability varies constantly due to magnetic influences
Solution Approach 1:
The patent replaces magnetic compasses that are susceptible to magnetic interference with an optical scene correlation system. The system uses visual feature matching between captured images and reference images to determine north reference, providing reliable and stable orientation data不受 magnetic influences while keeping the system lightweight.
4Measurement precision
If manual reticle alignment with north features is performed, then north reference can be established, but the process requires consummate skill and accuracy is questionable during battlefield conditions
Solution Approach 1:
The system performs automatic north reference establishment through scene correlation, eliminating the need for manual reticle alignment by soldiers. The correlation algorithm automatically identifies matching features between the captured image and reference image, calculates the rotational offset, and establishes north reference without requiring operator skill or intervention.
Solution Approach 2:
The scene correlation system provides automatic feedback by comparing the captured image with the reference image, calculating the angular offset, and adjusting the north reference accordingly. This closed-loop process eliminates manual alignment errors and provides consistent, accurate north reference even during dynamic battlefield conditions.
Data Source
AI summary
A scene correlation-based target system and related methods are provided. A reference image depicts a remotely-positioned object having identifiable characteristics, wherein a reference directional vector is established relative to the reference image. A target image of a general vicinity of the remotely-positioned object has an unknown directional vector, the target image having at least a portion of the identifiable characteristics. An inertial measuring unit has a scene correlation system, wherein the scene correlation system matches the portion of the identifiable characteristics of the target image with the identifiable characteristics of the reference image, wherein a slew angle between the reference image and the target image is calculated. A target image directional vector is derived from the calculated slew angle and the reference directional vector.