Leveling Rods

A leveling rod is a vertically supported tape used to measure vertical distance, which is the difference in elevation, between a line of sight and a required point above or below it. Although there are several types of rods, the most popular and frequently used is the Philadelphia rod. Figure 19 shows the face and back of this rod.

The Philadelphia rod consists of two sliding sections, which can be fully extended to a total length of 13.10 feet. When the sections are entirely closed, the total length is 7.10 feet. For direct readings, or readings on the face of the rod, of up to 7.10 and 13.10 feet, the rod is used extended and read on the back by the rodman. If you are in the field and don’t have a Philadelphia rod, you can use a 1 by 4 with a mark or a 6 foot wooden ruler attached to a 2 by 4.

In direct readings, the person at the instrument reads the graduation on the rod intercepted by the cross hair through the telescope. In target readings, the rodman reads the graduation on the face of the rod intercepted by a target. In Figure 19 the target does not appear; it is shown in Figure 20. It is a sliding, circular device that can be moved up or down the rod and clamped in position. The rodman places it on signals from the instrumentman.