Using Kinect to calculate distance traveled

Question

I'm trying to develop what seems to be a simple program that uses the Kinect for Xbox360 to calculate the distance traveled by a person. The room that the Kinect will be pointed at will be 10 x 10. After the user presses the button, the subject will move about this space. Once the subject reaches their final destination in the area, the user will press the button again. The Kinect will then output how far the subject traveled in between both button presses. Having never developed for the Kinect before, it's been pretty daunting to get started. My issue is that I'm not entirely sure what I should be using to measure the distance. In my research, I've found ways to calculate the distance an object is FROM the Kinect but that's about it.

Answer 1

What you have hear is a simple question of dealing with a Cartesian plane. The Kinect has 20 joints that exist in XYZ space, and distance is measured in meters. In order to access these joints, you have these statements inside a "Tracker" class (this is C#... not sure if you're using C# or C++ in the SDK):

public Tracker(KinectSensor sn, MainWindow win, string fileName)
        {
            window = win;

            sensor = sn;
            try
            {
                sensor.Start();
            }
            catch (IOException)
            {
                sensor = null;
                MessageBox.Show("No Kinect sensor found. Please connect one and restart the application", "*****ERROR*****");
                return;
            }

            sensor.SkeletonFrameReady += SensorSkeletonFrameReady;   //Frame handlers
            sensor.ColorFrameReady += SensorColorFrameReady;
            sensor.SkeletonStream.Enable();
            sensor.ColorStream.Enable();
        }

These access the color and skeleton streams from the Kinect. The skeleton stream contains the joints, so you focus on that with these statements:

//Start sending skeleton stream
        private void SensorSkeletonFrameReady(object sender, SkeletonFrameReadyEventArgs e)
        {
            //Access the skeleton frame
            using (SkeletonFrame skeletonFrame = e.OpenSkeletonFrame())
            {

                if (skeletonFrame != null)
                {
                    //Check to see if there is any data in the skeleton
                    if (this.skeletons == null)

                        //Allocate array of skeletons
                        this.skeletons = new Skeleton[skeletonFrame.SkeletonArrayLength];

                    //Copy skeletons from this frame
                    skeletonFrame.CopySkeletonDataTo(this.skeletons);

                    //Find first tracked skeleton, if any
                    Skeleton skeleton = this.skeletons.Where(s => s.TrackingState == SkeletonTrackingState.Tracked).FirstOrDefault();
                    if (skeleton != null)
                    {
                        //Initialize joints
                        ///<summary>
                        ///Joints to be displayed, projected, recorded, etc.
                        ///</summary>
                        Joint leftFoot = skeleton.Joints[JointType.FootLeft];
                    }
                }

So, at the beginning of your program, you want to pick a joint (there are 20... choose one that will ALWAYS be facing towards the Kinect when you are executing the program) and get its location with something like the following statements:

if(skeleton.Joints[JointType.FootLeft].TrackingState == JointTrackingState.Tracked)
{
    double xPosition = skeleton.Joints[JointType.FootLeft].Position.X;
    double yPosition = skeleton.Joints[JointType.FootLeft].Position.Y;
    double zPosition = skeleton.Joints[JointType.FootLeft].Position.Z;
}

At the end, you'll want to have a slight delay before you stop the stream... some time between the click and when you shut off the stream from the Kinect. You will then do the math you need to do to get the distance between the two points. If you don't have the delay, you won't be able to get your Cartesian point.