Algorithm

Section author: Luke Frisken <l.frisken@gmail.com>

The com.atc.simulator.prediction_service.engine.algorithms.java package contains all of the java implementations for the different algorithm types.

The most relavent algorithm employed in this project is in the algorithms.java.JavaLMLeastSquaresAlgorithmV3 class, and also worth checking out for understanding is algorithms.java.JavaPredictionAlgorithm.

Each time the algorithm is executed it uses the algorithms.java.AlgorithmState passed to it from the PredictionEngineThread from where it was stored in the PredictionEngineSystemStateDatabase keyed to the aircraft which is currently having its prediction created. It uses the AlgorithmState to store persisent state information about the algorithm between runs of the algorithm in WorkItems.

LMLeastSquaresV3 Algorithm

The algorithm in algorithms.java.JavaLMLeastSquaresAlgorithmV3 is the latest iteration. Old iterations are kept for reference and testing purposed.

This algorithm uses Levenberg-Marquardt Least Squares Circle Fit method to calculate a circle which matches recorded location points.

For an overview of this method of circle calculation, see the research done in Circle Fitting Research.

It also uses algorithms.java.JavaLinearAlgorithm to calculate a linear projection to submit in the prediction. Then a blending of the two prediction lines occurs to produce the centre line which is then passed with the other two lines for rendering in the Display

Action Diagram fo LMLeastSquaresV3 Algorithm