Passive Altimeter Using Image Displacement for Altitude
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Solution Overview
Problem
Conventional altimeters for determining altitude above ground level can be inaccurate due to signal distortion or interception, necessitating an improved method for precise altitude measurement.
Innovation Solution
A passive altimeter system utilizing an imaging device, groundspeed system, and image processing device to compare images taken at different positions, calculate altitude based on groundspeed, and account for Nadir angle, allowing for accurate altitude determination without active radar signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active radar signals are used for altitude measurement, then altitude can be determined, but the signals can be distorted, intercepted, or inaccurate
Solution Approach 1:
The patent inverts the conventional active radar approach by using a passive imaging device that captures images of the ground rather than transmitting radar signals. The system determines altitude by analyzing the displacement of ground features between images taken at different positions, eliminating the need for transmitted signals that can be distorted or intercepted.
Solution Approach 2:
The patent replaces the electromagnetic radar signal transmission system with an optical imaging system. Instead of using active radar waves to measure altitude, the system uses passive optical or infrared imaging to capture ground features and calculates altitude based on the geometric relationship between image displacement and aircraft motion.
2Reliability
If passive imaging is used to determine altitude, then signal reliability is improved, but the device complexity increases
Solution Approach 1:
The patent employs a groundspeed system that can determine groundspeed through multiple methods (GPS, inertial measurement units, or other means), making the system versatile and adaptable. This multi-functionality allows the same system to serve different operational requirements without increasing fundamental complexity.
Solution Approach 2:
The patent introduces an image processing device as an intermediary that automatically performs the complex task of comparing images, identifying common pixels, calculating displacement, and determining altitude. This intermediary handles the computational complexity, allowing the overall system to maintain reliability while managing device complexity through automation.
3Measurement precision
If image comparison is performed to determine altitude, then measurement precision is improved, but the loss of time increases
Solution Approach 1:
The patent performs preliminary actions by continuously capturing images and pre-processing them as the aircraft moves. The image processing device is ready to immediately compare new images with previous ones, reducing the time penalty by having images and processing routines prepared in advance rather than starting from scratch for each altitude measurement.
Solution Approach 2:
The system maintains continuous operation by continuously capturing images and continuously processing them to determine altitude. Rather than performing discrete, time-consuming measurements, the system operates continuously, ensuring that altitude information is always available with minimal delay while maintaining high precision through ongoing image comparison.
Data Source
AI summary
A passive altimeter includes an imaging device, a groundspeed system, an image processing device operatively connected to receive an indication of groundspeed from the groundspeed system and to receive at least a first image from the imaging device taken at a first position and a second image from the imaging device taken at a second position spaced apart from the first position. The image processing device is configured to compare the first image and the second image to determine an altitude above ground using the indication of groundspeed from the groundspeed system.