private void ComputeAccelerations(TimeSeriesCollection tsc, CalibrationHelper calibrationHelper, Func <int, PointF> getCoord)
{
if (tsc.Length <= 4)
{
PadAccelerations(tsc);
return;
}
// First pass: average speed over 2t centered on each data point.
for (int i = 2; i < tsc.Length - 2; i++)
{
float t = calibrationHelper.GetTime(2);
double acceleration = (tsc[Kinematics.LinearSpeed][i + 1] - tsc[Kinematics.LinearSpeed][i - 1]) / t;
tsc[Kinematics.LinearAcceleration][i] = calibrationHelper.ConvertAccelerationFromVelocity((float)acceleration);
double horizontalAcceleration = (tsc[Kinematics.LinearHorizontalVelocity][i + 1] - tsc[Kinematics.LinearHorizontalVelocity][i - 1]) / t;
tsc[Kinematics.LinearHorizontalAcceleration][i] = calibrationHelper.ConvertAccelerationFromVelocity((float)horizontalAcceleration);
double verticalAcceleration = (tsc[Kinematics.LinearVerticalVelocity][i + 1] - tsc[Kinematics.LinearVerticalVelocity][i - 1]) / t;
tsc[Kinematics.LinearVerticalAcceleration][i] = calibrationHelper.ConvertAccelerationFromVelocity((float)verticalAcceleration);
}
PadAccelerations(tsc);
// Second pass: extra smoothing derivatives.
// This is only applied for high speed videos where the digitization is very noisy
// due to the combination of increased time resolution and decreased spatial resolution.
double constantAccelerationSpan = 50;
MovingAverage filter = new MovingAverage();
double[] averagedAcceleration = filter.FilterSamples(tsc[Kinematics.LinearAcceleration], calibrationHelper.CaptureFramesPerSecond, constantAccelerationSpan, 2);
double[] averagedHorizontalAcceleration = filter.FilterSamples(tsc[Kinematics.LinearHorizontalAcceleration], calibrationHelper.CaptureFramesPerSecond, constantAccelerationSpan, 2);
double[] averagedVerticalAcceleration = filter.FilterSamples(tsc[Kinematics.LinearVerticalAcceleration], calibrationHelper.CaptureFramesPerSecond, constantAccelerationSpan, 2);
for (int i = 0; i < tsc.Length; i++)
{
tsc[Kinematics.LinearAcceleration][i] = averagedAcceleration[i];
tsc[Kinematics.LinearHorizontalAcceleration][i] = averagedHorizontalAcceleration[i];
tsc[Kinematics.LinearVerticalAcceleration][i] = averagedVerticalAcceleration[i];
}
}
private void ComputeAccelerations(TrajectoryKinematics kinematics, CalibrationHelper calibrationHelper)
{
if (kinematics.Length <= 4)
{
PadAccelerations(kinematics);
return;
}
// First pass: average speed over 2t centered on each data point.
for (int i = 2; i < kinematics.Length - 2; i++)
{
PointF p0 = kinematics.Coordinates(i - 2);
PointF p2 = kinematics.Coordinates(i);
PointF p4 = kinematics.Coordinates(i + 2);
float t02 = calibrationHelper.GetTime(2);
float t24 = calibrationHelper.GetTime(2);
float t13 = calibrationHelper.GetTime(2);
double acceleration = (kinematics.Speed[i + 1] - kinematics.Speed[i - 1]) / t13;
kinematics.Acceleration[i] = calibrationHelper.ConvertAccelerationFromVelocity((float)acceleration);
double horizontalAcceleration = (kinematics.HorizontalVelocity[i + 1] - kinematics.HorizontalVelocity[i - 1]) / t13;
kinematics.HorizontalAcceleration[i] = calibrationHelper.ConvertAccelerationFromVelocity((float)horizontalAcceleration);
double verticalAcceleration = (kinematics.VerticalVelocity[i + 1] - kinematics.VerticalVelocity[i - 1]) / t13;
kinematics.VerticalAcceleration[i] = calibrationHelper.ConvertAccelerationFromVelocity((float)verticalAcceleration);
}
PadAccelerations(kinematics);
double constantAccelerationSpan = 50;
MovingAverage filter = new MovingAverage();
kinematics.Acceleration = filter.FilterSamples(kinematics.Acceleration, calibrationHelper.CaptureFramesPerSecond, constantAccelerationSpan, 2);
kinematics.HorizontalAcceleration = filter.FilterSamples(kinematics.HorizontalAcceleration, calibrationHelper.CaptureFramesPerSecond, constantAccelerationSpan, 2);
kinematics.VerticalAcceleration = filter.FilterSamples(kinematics.VerticalAcceleration, calibrationHelper.CaptureFramesPerSecond, constantAccelerationSpan, 2);
}
