Surface model from xyz

I have scanned a rail line with x, y and z points. I want to make a triangular surface model, so i can make bounderies and calculate the voloume of the surface within the bounderies. i have tried to do it with all the stand surf functions in matlab, but cant get any satisfying results. I have serched the web and tried to do it, in the last week. Does any of you guys know what is the way to do it, or have a script? I can send the datafiles, if it is needed.

thanks in advance.