We have a procedure for determining the distortion for your camera, using JavaCV. See this thread
http://chiefdelphi.com/forums/showthread.php?t=101753
Our answer was xc= x*(1 -0.055*r^2 ), and yx = y*(1 - 0.55*r^2), where r is the distance from the center of the image, and x,y is the pixel location from the center of the image. This number is for the Axis 1011 camera.
You may use this value either during photo processing or after you get your points, depending on the image processing load you can support.
Other calibration techniques exist; this is just the one we used.