144 28 92 2 : n: (Earth Grid) ANSI/IEEE Std 80-1986 Eq.42 Rg ( ) ( -M) L' (M) d' (M) h : (M) 2 A (M ) K1= -0.04( / )+1.41 K2 = 0.15( / )+5.5 ' : , ' =1.09 ( ) ( ) ( )