draw a rectangle on the ground sufficiently large so that you can develop a large grid with say 2'x2' or whatever measuring system you are using inches milimeters cubits parsecs whatever.
The grid should already be a group. right click. edit group. mouse over grid. look at vcb to see radius of influence. type in preferred radius. mouse over grid. left click hold and drag upward or downward on screen (assuming you are in normal 3d view and not in some ortho view).
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