If I am interpreting your question right, you want to vectorize three 11x11 grids of the coordinate directions to make a 121x3 matrix.
[Xgrid,Ygrid]=meshgrid(0:800:8000,0:800:8000);
Zgrid=100*ones(11,11);
x=reshape(Xgrid,[],1); % reshape x into a vector
y=reshape(Ygrid,[],1); % reshape y into a vector
z=reshape(Zgrid,[],1); % reshape z into a vector
XYZ=[x y z]; % Combine the vectors into a matrix
Alternatively, you can simply assign the grids in a 3D array before reshaping
[Xgrid,Ygrid]=meshgrid(0:800:8000,0:800:8000);
Zgrid=100*ones(11,11);
XYZ(:,:,1)=Xgrid;
XYZ(:,:,2)=Ygrid;
XYZ(:,:,3)=Zgrid;
XYZ=reshape(XYZ,121,3);
