Airspace Encounter Models Updates - October 2021

For many aviation safety studies, aircraft behavior is represented using encounter models, which are statistical models of how aircraft behave during close encounters. They are used to provide a realistic representation of the range of encounter flight dynamics where an aircraft collision avoidance or detect and avoid system would be likely to alert.?Since 2019, software related to these models have been released under permissive open source licenses to promote community development and enable commercialization.

Today we updated four repositories.?

em-model-manned-bayes (link)

Version 2.0 introduces object-oriented programming in MATLAB with a class for a generic encounter model and classes specific to the uncorrelated conventional aircraft and correlated terminal models. These classes enable the user to easily read in the ASCII parameter files with improved input handling. New example run scripts are included to demonstrate how to use the OOP classes. With a few lines of code, the uncorrelated and terminal model can be sampled or generate aircraft trajectories in a local Cartesian coordinate system. The uncorrelated model also supports generating tracks and translating them into a geodetic coordinate system. Rejection sampling based on speed has also been improved for the uncorrelated encounter model by defining minimum and maximum permitted speeds based on the individual probability distribution of the speed bins, rather than the minimum and maximum speeds of the overall model structure. Additional improvements to rejection sampling are scheduled for a future release.

Classes are not yet available for the RADES-based correlated, ETMS-based due regard, DFDR-based HAA, and most unconventional models.

em-pairing-uncor-importancesampling (link)

This repository has been updated to use the uncorrelated encounter model class from em-model-manned-bayes. We also moved the 6DOF dynamics simulation to em-core, so that the dynamics simulation can be better leveraged by other encounter model repositories. The update also includes various quality of life updates, such as improved property validation.

em-core (link)

Version 1.2 now redistributes a third party function, allcomb, to help reduce dependences on MATLAB toolboxes and also an updated 6DOF dynamics simulation originally hosted in em-pairing-uncor-importancesampling. The dynamics simulation now has two additional inputs corresponding to dynamic limit constraints. We updated msl2agl, the function that uses digital elevation models to calculate the mean sea level (MSL) elevation of terrain or estimate the above ground level (AGL) altitude of inputted geodetic coordinates. These changes focus on improving data handling and replacing a function scheduled to be deprecated by Mathworks in the future. Furthermore, a run script has been added to help streamline compiling MATLAB mex functions.

em-pairing-geospatial (link)

Similar to em-pairing-uncor-importancesampling, this repository was updated to use the uncorrelated encounter model class from em-model-manned-bayes. Pre-generated files of tracks generated from the Bayesian encounter models are no longer required to create encounters; instead, tracks are now generated using the uncorrelated encounter model class at runtime. Additionally, trajectories are now formatted as Matlab Timetables for improved interpolation, smoothing, outlier detection, and time-based sampling. The use of Timetables prompted the removal or modification of functions whose capabilities were deprecated by the built-in capabilities of Timetables.?

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? 2021 Massachusetts Institute of Technology.

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This material is based upon work supported by the Federal Aviation Administration under Air Force Contract No. FA8702-15-D-0001. ?Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Federal Aviation Administration.

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