range-pole

from The Century Dictionary.

• noun In surveying, one of two or three slender rods or staffs (prominently painted or marked, and usually sharpened at one end or provided with a pointed shoe or with a tripod by which it may be placed firmly in or on the ground in a vertical position) used for the purpose of prolonging a straight line by setting the third pole or locating a point in the straight line through the other two prolonged.
• noun In rough surveying, a method by which one may place himself on a straight line between two distant visible points, by moving two range-poles into successive positions until the straight line through the two poles passes through the two distant points simultaneously.