MATLAB: Area of curved surface

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Hi,
I have data points belonging to a surface in 3D. I want to calculate the surface area of it. What are my options? If possible computationally inexpensive solutions are preferred. The way I have done it so far is to fit a plane into the points, project the boundary points onto the plane and calculate the area of the resulting polygon. But I want something more precise. The X and Y data are on a regular grid, the Z data not. All three are floats.