Point Cloud edge detection

Hi everyone,

I have some images that are taken of a cylindrical sample which I require to model in order to obtain its volume. By taking thin slices from the cylinder, I am able to obtain the radius using a Gauss-Newton algorithm from the cross-sectional point clouds.

As for the height variation along the cylinder(which may not be vertical), what I would like to do is to trace out the edges that define the cylinder. I tried using the guide from this link:http://www.mathworks.com/help/images/analyzing-images.html#f11-31392

However, it traces some unwanted boundary as well on my image. Is there any way to define a certain extents to which the boundary should be created? Also, how could I then fit a curve through the boundary with its corresponding equations?

Thanks in advance.

[Image Analyst]

Where did you upload your image? Try http://snag.gy or http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers