Vertical Motion Detector Using Lag Function Residuals
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Solution Overview
Problem
Current air traffic control systems face limitations in accurately determining vertical motion of aircraft due to low resolution Mode C transponder data and altitude post-processing methods, leading to delayed and uncertain altitude change detection, which compromises safety by missing real conflicts and falsely declaring others.
Innovation Solution
A method involving a lag function with a moving average of altitude data to detect vertical motion by calculating residuals and comparing them against a threshold, allowing for early detection of changes from level to non-level flight, using a radar system processor with a vertical motion detector module to initiate tracking and output vertical motion indicators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional altitude post-processing methods are used with Mode C transponder data, then the system can process altitude information, but the detection precision and response speed are degraded due to 100-foot quantization resolution and delayed altitude change detection
Solution Approach 1:
The patent applies preliminary action by performing velocity estimation through residual analysis before formal altitude change detection. The system calculates residuals between actual altitude measurements and predicted altitudes from a lag function, accumulating these residuals to detect vertical motion onset before conventional methods would register the change. This preliminary velocity estimation enables earlier detection of altitude changes, reducing the detection delay inherent in conventional post-processing approaches that wait for quantized altitude thresholds to be crossed.
2Reliability
If conventional altitude post-processing methods are used with Mode C transponder data, then the system can process altitude information, but the measurement precision is degraded due to 100-foot quantization resolution and finite altitude jumps
Solution Approach 1:
The patent introduces an intermediary approach by using a lag function as a predictive model that smooths the quantized Mode C altitude data. Instead of directly processing the stepped 100-foot quantized values, the system compares actual measurements against predictions from the lag function, calculating residuals that represent the deviation from expected behavior. This intermediary residual analysis method filters out the artificial discontinuities caused by quantization while preserving genuine vertical motion signals, thereby improving measurement precision without sacrificing reliability.
3Reliability
If minimum altitude change limits and filtering delays are applied, then false alerts are reduced, but real aircraft position conflicts are missed and detection accuracy is compromised
Solution Approach 1:
The patent implements feedback by continuously comparing actual altitude measurements against predictions from the lag function and using the residuals to update the detection state. The system accumulates residuals over time and uses this feedback to determine when vertical motion has commenced, allowing dynamic adjustment of detection sensitivity. This feedback mechanism enables the system to detect genuine conflicts more quickly while maintaining reliability, as the accumulated residual provides evidence that distinguishes real vertical motion from quantization artifacts without requiring fixed minimum altitude change limits or arbitrary filtering delays.
Data Source
AI summary
Methods and apparatus for vertical motion detection of objects, such as aircraft. In one embodiment, a method comprises receiving altitude data for an object, determining a residual of a lag function, wherein the lag function comprises a moving average of the altitude data for the object, and wherein the residual corresponds to a difference between a value for the lag function and the object altitude data at a given time such that the residual grows in magnitude over time in response to the object transitioning from level flight to vertical motion, detecting vertical motion of the object by comparing a sum of data derived from the residuals against a threshold value, and outputting a vertical motion indicator after detecting the vertical motion of the object.