Passive Altimeter Triangulation Using IR Sensor Distortion
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Solution Overview
Problem
Determining the altitude of a mobile platform, such as a helicopter, is challenging in GPS-denied environments and when using a laser range finder is undesirable due to the risk of attracting additional threats.
Innovation Solution
Incorporating a terrain map obtained from overhead satellite imagery to triangulate the altitude using known distances between objects and angular space distortion parameters in the sensors of an infrared countermeasure system, allowing for altitude determination without GPS or laser range finder reliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS signals are used to determine altitude, then altitude measurement is accurate and reliable, but GPS signals can be easily jammed by enemy forces causing signal denial
Solution Approach 1:
The patent uses terrain maps and sensor imagery as intermediary elements to determine altitude indirectly. Instead of directly receiving GPS signals, the system captures images of terrain features, compares them with stored terrain maps, and calculates altitude based on the matching features and known terrain elevations. This intermediary approach bypasses the need for direct GPS signal reception while still providing reliable altitude information.
2Measurement precision
If a laser range finder is used to determine altitude, then altitude measurement is accurate, but the laser emission can identify the location of the platform inviting additional threats
Solution Approach 1:
The patent converts the harmful effect of needing active illumination (laser) into a beneficial passive imaging approach. Instead of emitting laser light that could be detected, the system uses passive infrared or optical sensors to capture images of terrain features. The same sensors that detect thermal signatures of missiles are repurposed to capture terrain imagery for altitude determination, turning a vulnerability into an advantage.
Solution Approach 2:
The patent makes the existing missile detection sensors serve multiple functions. These sensors are used both for their original purpose of detecting incoming threats and for capturing terrain imagery to determine altitude. This multi-functionality eliminates the need for separate laser range finders while maintaining measurement capabilities using already-deployed hardware.
3Ease of operation
If traditional altimeters are used in GPS-denied environments, then altitude can be determined, but the available methods either rely on jammed GPS or emit detectable laser signals
Solution Approach 1:
The patent implements a dynamic system that adapts its operation based on environmental conditions. The system continuously monitors for GPS signal availability and automatically switches between GPS-based altitude determination and passive imaging-based determination. This dynamic adaptation ensures continuous operational capability across different environmental conditions without requiring manual intervention or system reconfiguration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate altitude calculation in GPS-denied environments, enhancing safety by avoiding the detection risks associated with laser range finders and providing a reliable altimeter system for mobile platforms.
Implementation Method 1
at least one sensor carried by the platform to capture a first image
Implementation Method 2
triangulating the altitude of the platform based on the known distance between two objects obtained from the terrain map and pre-determined and known angular space distortion parameters
Data Source
AI summary
A passive altimeter system comprising an angle between a point and a central boresight that is determined from distortion parameters of a lens in an infrared sensor in a countermeasure system on a mobile platform wherein the infrared sensor captures a first image for determining a distance between the platform and one of (i) a ground surface and (ii) a target, and the passive altimeter system further comprising a dimensional distance between two points in the first image that is determined from a secondary source external to the countermeasure system, and a processor to triangulate the distance between the platform and one of (i) the ground surface and (ii) the target based on the dimensional distance and the angle.