How to find coordinates of the polynomial surface?

Hallo, I have a problem with polynomial surface, and in this surface i have x,y (in each point of surface) and the angle btw them (alpha) how should i find z? in the case that z in each point is normal to the unit vector of the surface?

Answer 1

[Image Analyst]

This is what I use: http://www.mathworks.com/matlabcentral/fileexchange/34765-polyfitn