Surface Area from irregular 3D surface

I have a set of irregular 3D cartesian coordinates that make an irregular surface. I have managed to overlay a 51x49 matrix and interpolate in-between providing enough point in order to generate a surface.

var = [X,Y,Z];

t=1;
for i=1:size(var,1)
  if (var(i,1)<0 && var(i,2)>0 && var(i,3)<0)
      negXposYnegZ(t,:)=(var(i,:));
      t=t+1;
  end
end

   x3 = negXposYnegZ(:,1);
   y3 = negXposYnegZ(:,2);
   z3 = negXposYnegZ(:,3);

   [xData3, yData3, zData3] = prepareSurfaceData( x3, y3, z3 );

   % Set up fittype and options.
   ft = 'linearinterp';

   % Fit model to data.
   [fitresult3, gof] = fit( [xData3, yData3], zData3, ft, 'Normalize', 'on' );

   plot(fitresult3);

   h = gcf; %current figure handle
   axesObjs = get(h, 'Children');  %axes handles
   dataObjs = get(axesObjs, 'Children'); %handles to low-level graphics objects in axes
   objTypes = get(dataObjs, 'Type');  %type of low-level graphics object
   xdata3 = get(dataObjs, 'XData');  %data from low-level grahics objects
   ydata3 = get(dataObjs, 'YData');
   zdata3 = get(dataObjs, 'ZData');

   vector6 = reshape(xdata3.',[],1);
   vector7 = reshape(ydata3.',[],1);
   vector8 = reshape(zdata3.',[],1);

   close all;

   totalvector3 = [vector6,vector7,vector8];

   ans3 = totalvector3(~any(isnan(totalvector3),2),:);

   ansx3 = ans3(:,1);
   ansy3 = ans3(:,2);
   ansz3 = ans3(:,3);if true

   scatter3(ansx3,ansy3,ansz3);

generates the following result

This can be represented as a surface, generating the following result

I can't use alphaShape as it provides an area for the whole shape, not just the surface

Any body know a way to find the area of the surface plot?

Thanks in advance