// Calibration contain methods for finding and validating factors transforming GPS coordinates to meters.
            // ToDo: make static

            public static bool ShouldAltBeUsed(TrainingSession ts)
            {
                Calibration         calibrationWithAlt = new Calibration(true);
                List <TickDiffPair> calibrationSet     = calibrationWithAlt.FindCandidates(ts, 100);
                List <TickDiffPair> validationSet      = calibrationWithAlt.FindCandidates(ts, 100);

                ConversionFactors estimationWithAlt = calibrationWithAlt.CalibrateIteratively(calibrationSet, validationSet);
                double            errorWithAlt      = calibrationWithAlt.CalculateCalibrationError(estimationWithAlt, validationSet);

                Calibration       calibrationWithoutAlt = new Calibration(false);
                ConversionFactors estimationWithoutAlt  = calibrationWithoutAlt.CalibrateIteratively(calibrationSet, validationSet);
                double            errorWithoutAlt       = calibrationWithAlt.CalculateCalibrationError(estimationWithoutAlt, validationSet);

                return(errorWithAlt < errorWithoutAlt);
            }