is it possible to find the distance between the legs of a walking person using MATLAB?

is it possible to find the distance between the legs of a walking person using MATLAB? human walking video is the input..

[Walter Roberson]

Is the walking person a fixed distance away? Are they walking at a fixed angle? Are there ground markings that could be used to determine the distance?

[Cedric]

Could you put color patches or e.g. infra red LEDs on their legs, or are these random persons?

Answer 1

[Anchit Dhar]

As an alternative, you can use Skeletal tracking with the Kinect for Windows sensor. This problem will get reduced to distance computation between the ankle/Knee joints(3D points), whichever fits your definition for distance.

Note: Kinect for Windows is supported in MATLAB through Image Acquisition Toolbox, R2013a onwards.

[Walter Roberson]

I wonder how well Kinect does on calculating distance away?

[Sivakumaran Chandrasekaran]

@ Anchit.. Kinect looks cool. I dont have much details about the integration of MATLAB with it, but the device is good.but more costlier.

[Anchit Dhar]

@Walter: From what I have observed while working with Kinect for Windows, it does a very good job of localizing the joint coordinates. But then, it all depends on what accuracy are you looking for.

@Siva: Here is a link to the example for getting the joint coordinates from a Kinect for Windows sensor using MATLAB & Image Acquisition Toolbox:

http://www.mathworks.com/help/imaq/examples/using-the-kinect-r-for-windows-r-from-image-acquisition-toolbox-tm.html

Answer 2

[Walter Roberson]

No. You cannot determine the distance between legs of someone in a hoop skirt with a sufficiently long train.

See, e.g., http://i62.photobucket.com/albums/h89/zellybell/Dresses/HoopSkirt.jpg

[Cedric]

And there are a few limit cases where it is irrelevant anyway..

[Walter Roberson]

Hee, yes, that is called "walking" in English :)

[Cedric]

In French too actually ;-) "marcher sur les mains"

Answer 3

[Jan]

How is "distance between legs" mathematically defined? Legs consists of at least 3 rigid segments (simulating the 26 bones of the feet seems to be over-doing here) with a spatial extent. While the distnace between the hip-joint centers is (almost) constant, the "distance" between the lower leg segments or the feet needs a meaningful definition before we can discuss, if this can be determined by a 2D-projected movie.

[Walter Roberson]

My speculation: the poster is trying to analyze stride length.

[Sivakumaran Chandrasekaran]

@Jan.. distance between first feet and second feet

[Jan]

Or step width?

[Walter Roberson]

What would be done with the distance information? Knowing that would give us a better idea of what needs to be measured.

You could upload some sample frames, http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers

[Sivakumaran Chandrasekaran]

I will work on this project by tomorrow. So, I shall collect more datas and sample frames and upload it by tomorrow.

[Walter Roberson]

Okay, but in the meantime, telling us what you will do with the distance information will allow us to be thinking about how we might deal with the problem.

[Sivakumaran Chandrasekaran]

http://imageshack.us/gal.php?id=q5qskqSpnpytlK6cmd3W06g

you can find two image. input is a color video in which a man is walking. how to compare the extracted patterns by measuring the distance.

[Walter Roberson]

Unfortunately imageshack is requiring an account in order to view the images.

[Jan]

@Sivakumaran Chandrasekaran: The problem of the "distance" is still not cleared: Do you mean the 3D-distance between the center of the feet in each frame of the movie? Or the distance between the points on the floor, where the heels get ground contact during walking? While the first distances varies from frame to frame, the second distance varies from stride to stride.

Note that it is very hard to define the center of a foot exactly, most of all in 3D.