Dictionary:Straight slope measurement
The source depth is given by the horizontal distance over which a magnetic anomaly is nearly linear at the maximum slope, divided by an index value. Indices are 1.9 for a vertical or horizontal thin sheet, 1.7 for a thick sheet, 1.4 for a pluglike body, 1.3 for a wide body, 1.2 for a contact, and 1.5 as a default value. Also called maximum slope distance, Vacquier rule, Steenland-Vacquier rule. See Figure D-10 and depth rule.