/**
* Creates a position step with image coordinates. Overridden by ParticleDataTrack.
*
* @param track the PointMass track
* @param n the frame number
* @param x the x coordinate
* @param y the y coordinate
* @return the PositionStep
*/
protected PositionStep createPositionStep(PointMass track, int n, double x, double y) {
PositionStep newStep = new PositionStep(track, n, x, y);
newStep.valid = !Double.isNaN(x) && !Double.isNaN(y);
return newStep;
}
