Synthetic Digital Sextant for GPS-Denied Navigation
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Solution Overview
Problem
Existing navigation systems face challenges in providing absolute, high-accuracy, all-weather positioning without relying on GPS, especially in GPS-denied areas, and struggle to effectively cancel out line-of-sight biases and atmospheric refraction errors.
Innovation Solution
The Synthetic Digital Sextant (SDS) technology uses an electro-optical infrared (EO/IR) sensor to measure celestial objects and a Low Earth Orbit satellite, synthesizing differential angular measurements to determine platform location, incorporating a Kalman filter for data fusion and inertial measurements to cancel out biases and errors, enabling GPS-like accuracy in GPS-denied environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS is used for navigation, then positioning accuracy is improved, but reliability deteriorates in GPS-denied areas
Solution Approach 1:
The patent introduces an intermediary system (synthetic digital sextant) that mediates between the need for GPS-like accuracy and the requirement for operation in GPS-denied environments. This system uses celestial navigation as a bridge, combining traditional sextant measurements with modern digital processing and sensor fusion to provide reliable positioning when GPS is unavailable.
Solution Approach 2:
The system changes the fundamental parameters of navigation by transitioning from radio-frequency GPS signals to optical celestial observations. By measuring angular positions of celestial bodies and synthesizing horizon lines from satellite observations, the system achieves positioning capability across different environmental conditions where GPS fails.
2Reliability
If traditional sextant is used for celestial navigation, then reliability is improved in GPS-denied areas, but measurement precision deteriorates due to line-of-sight biases and atmospheric refraction
Solution Approach 1:
The patent replaces the mechanical optical system of traditional sextants with an electro-optical infrared sensor system. This substitution enables digital capture and processing of celestial body images, allowing for precise coordinate extraction and computational correction of atmospheric effects that limit traditional mechanical sextants.
Solution Approach 2:
The system implements feedback through Kalman filtering that continuously compares observed celestial positions with predicted positions, using the differences to correct for line-of-sight biases and atmospheric refraction. This closed-loop approach progressively improves measurement precision while maintaining reliability in GPS-denied environments.
3Measurement precision
If electro-optical infrared sensor is used to measure celestial objects, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the electro-optical infrared sensor multi-functional by using it for both primary mission operations and celestial navigation. This universality reduces overall system complexity by eliminating dedicated navigation hardware, as the same sensor serves dual purposes: main mission sensing and celestial body observation for positioning.
Solution Approach 2:
The system merges celestial navigation functionality with the primary mission sensor system, combining what would traditionally be separate subsystems. By integrating horizon line synthesis from satellite observations with celestial body tracking, the system reduces component count and simplifies architecture while maintaining high measurement precision.
4Measurement precision
If Kalman filter is used for data fusion, then measurement precision is improved by canceling biases, but computational complexity increases
Solution Approach 1:
The patent applies partial action by using the Kalman filter selectively for correcting specific bias parameters (line-of-sight and atmospheric refraction) rather than processing all navigation data through complex algorithms. This targeted approach achieves sufficient positioning accuracy without the full computational burden of exhaustive state estimation.
Data Source
AI summary
Technology for determining a position of a platform is described. A location of a horizon line can be determined using a sensor onboard the platform. One or more celestial objects in the sky can be detected using the sensor onboard the platform. Differential angular measurements between the horizon line and at least one of the celestial objects in the sky can be determined over a duration of time. The position of the platform can be determined based on the differential angular measurements between the horizon line and the celestial objects.