Surface area of a Contour

If a helpful soul can answer some questions regarding this script, http://www.mathworks.com/matlabcentral/fileexchange/6905-contour-area-calculation

I tried the script with some regular geometry cylindrical pillars, the surface area was not coming out to be correct. So let's suppose we have this contour: http://i.imgur.com/89KoR.png. 1) If i run the script such that the contour level entered is minimum value of the matrix, will it give me the surface area of the whole contour. 2) If i cut this contour at a given value, will it fill the cut-off portion with some flat plain areas? 3) Can the z-pixel calibration be defined?

The troubles of being a novice.

Also, does anybody else have an idea of calculating surface area of an irregular shape?