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Section 1  Preparing to Build
Using multiple readings
When laying out steeply sloped building plots or
carrying a benchmark to the building site, it will likely
be necessary to set up the instrument in several
locations. Figure 6-20 shows how reading from two
positions is used to calculate, establish, or determine
differences in grade at various locations on the plot.
1. Set up the instrument midway between two
points on the plot. In Figure 6-20, these are
identified as points A and B.
2. Take a line-of-sight reading at point A (or
station A). Record the reading in the notebook.
In this case, the reading is 5′-8″.
3. With the rod at point B and the instrument still
at setup #1, take a second reading. Record the
reading in the notebook. In this instance, the
reading is 2′-6″.
4. Move the instrument to a point midway between
points B and C. Level it as before.
5. Take a second reading on point B and record it.
In this example, the reading is 6′-0″.
6. With the rod located at point C, take a reading
by rotating the telescope 180°. Note and record
the elevation. In this case, the reading is 2′-4″.
7. Calculate the differences in grade level for
each pair of stakes, as shown in Figure 6-20.
8. Add the resulting distances and subtract the
“minus” sum from the “plus” sum to find the
difference in grade from one edge of the plot to
the other. The result, in this example, is 6′-10″.
Required grade elevation
Required
grade elevation
C
2'-4"
1'-10"
Grade stake
mark
Mark
1'-10"
2'-4"
F
Figure 6-19. Cut and fill stakes are used to tell the
excavator how much material must be removed or
added to reach grade level. The letter C means “cut”
(remove) and the letter F means “fill” (add).
6'-0"
2'-6" 5'-8"
Curbing
used as
benchmark
A
B
(Minus reading)
C
2'-4"
Setup #1
Setup #2
Setup #
1
2
Sum
Plus sight
5'-8"
6'-0"
11'-8"
Minus sight
2'-6"
2'-4"
4'-10"
Surveyor s Notebook
11'-8" – 4'-10" = 6'-10"
Figure 6-20. When there is a large slope on the property or when long distances are involved, the transit will need
to be set up in two or more locations.