[10 x 10]=>[30 x 40], interp err = 1.7559e+00
[20 x 20]=>[60 x 80], interp err = 3.1952e-01
[40 x 40]=>[120 x 160], interp err = 6.1821e-02
[80 x 80]=>[240 x 320], interp err = 1.3690e-02