LDACS Air-Ground Cooperative Positioning for Terrain Occlusion
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Solution Overview
Problem
Current Alternative Positioning, Navigation, and Timing (APNT) systems face challenges in providing accurate positioning and integrity monitoring, especially under terrain occlusions and low-altitude conditions, where GNSS signals are unavailable, leading to inaccuracies and difficulties in aircraft positioning.
Innovation Solution
A LDACS-based air-ground cooperative positioning method that classifies users into super-high, high, and low altitudes, utilizing information exchange and LDACS two-way ranging to enhance positioning accuracy and integrity monitoring, combining air-to-air and air-to-ground positioning results, and implementing fault detection algorithms to improve positioning and integrity assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If APNT services are implemented using limited ground ranging sources for high-altitude users, then positioning can be obtained, but the positioning reliability is not sufficient
Solution Approach 1:
The patent combines air-to-air positioning and air-to-ground positioning into a unified cooperative positioning system. High-altitude users share their positioning results with low-altitude users, and ground ranging sources provide additional measurements, creating a merged positioning solution that improves both accuracy and reliability compared to using limited ground sources alone.
Solution Approach 2:
The patent transitions from traditional ground-based positioning to a three-dimensional air-ground-cooperative positioning system by introducing airborne ranging sources at multiple altitude levels. This adds vertical dimensionality to the positioning geometry, improving positioning reliability and accuracy especially in terrain occlusion scenarios.
2Measurement precision
If APNT services are implemented for low-altitude users in canyon airports, then positioning is attempted, but the occlusion of ranging sources makes implementation difficult and accuracy low
Solution Approach 1:
The patent introduces high-altitude airborne users as intermediary ranging sources for low-altitude users in canyon airports. These airborne intermediaries can observe ground ranging sources that are occluded from the low-altitude user's perspective, relaying positioning information that overcomes the terrain occlusion problem.
Solution Approach 2:
By positioning ranging sources in the air at higher altitudes, the system escapes the two-dimensional ground plane constrained by canyon terrain. This vertical dimensionality change allows ranging sources to be positioned above occluding terrain features, providing unobstructed signal paths to low-altitude users.
3Ease of operation
If air-to-air positioning is used for low-altitude users, then positioning can be achieved, but the accuracy is significantly different from conventional GNSS positioning
Solution Approach 1:
The patent merges air-to-air positioning results with air-to-ground positioning results in a combined cooperative positioning solution. This fusion of multiple positioning modes leverages the availability advantage of air-to-air positioning while compensating for its accuracy limitations through the additional constraints provided by ground ranging sources.
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
The method provides more accurate positioning for low-altitude aircraft, such as those at canyon airports, and effectively monitors integrity, narrowing the gap between APNT and GNSS positioning accuracy, while reducing the need for extensive ground facilities.
Implementation Method 1
a distance between a ranging source and an aircraft is estimated according to the following formula: r(m)=(t2−t1)×v where t1 is the time of a query; t2 is the response time of a query response; v is a signal propagation speed.
Data Source
AI summary
The present invention provides a LDACS-based air-ground cooperative positioning method. According to the method, on the basis of LDACS, users are classified into super-high-altitude users, high-altitude users, and low-altitude users, and air-ground cooperative positioning is implemented through information exchange among the users at the three levels. Meanwhile, a new fault mode and an integrity hazard are introduced into the method. Therefore, the present invention further provides a method for monitoring the integrity of a LDACS-based air-ground cooperative positioning method, including a fault detection algorithm and a protection level solving method; and proposes a method for evaluating the complexity of integrity monitoring. The LDACS-based air-ground cooperative positioning method provided in the present invention well solves the problem of the shortage of APNT services in poor terrain conditions, making the positioning results more accurate.