the units in which magnetic survey maps are contoured. 1 nanotesla = 10-⁹ tesla. 1 nanotesla = 10-⁹ weber/m². 1 nanotesla = 10-¹ lines/m². 1 nanotesla = 10-⁵ lines/cm². 1 nanotesla = 10-⁵ gauss, 1 nanotesla = 1 gamma.