Surveying - Carpenter's and Builder's Math, Plans, and Specifications - page 206

Methods of Leveling
The simplest type of leveling is to find the difference in level between
two points that are visible from a third point, the difference in level
being less than the length of the leveling rod (see Figure 6-4).

B

A

Figure 6-4 Leveling between two points whose difference in
level is less than the length of the rod.

1. Set up and level the instrument at some point approximately
halfway between the two points.
2. Have a worker hold the rod vertically on one of the points,
and move the target up and down until its center coincides
with the crosshairs of the level.
3. Take a reading. This is the HI, or height of the instrument
above the benchmark A .

4.

Turn the telescope on its spindle, have the rod held on the other
point, and take a similar reading at B . The difference in level
is equal to the difference in the readings.

5.

If the difference in level is greater than the length of the rod, use
the method shown in Figure 6-5. Divide the distance between
the two points into sections of such length that the difference in
level between the dividing points A

B , and C (called stations )
are less than the length of the rod. Set up and level between
points A and B

,

.
6. Measure the distance Aa that is called backsight . Then, reverse
the telescope, and take reading Bb that is called foresight .