e. The rear stretcher man holds the rear stretcher in position while the tension is applied, so that the
rear terminal mark on the tape is opposite to or slightly forward of the mark on the copper strip on the
rear stake. He approaches the rear stake and places the staff firmly in the ground at the proper distance,
directly in line with the other stakes, while he simultaneously slips on the leather loop to the proper
height on the staff. To maintain steady pressure on the staff, the rear stretcher man should have the top
back of the staff resting on one of his shoulders, with his body leaning forward. With full tension
applied, the tape should be a few millimeters above the top of the stake.
f. The middleman is primarily concerned with the intermediate stakes along the baseline. He must
move forward, carrying the tape, and place it on the middle support as tension is applied. If a nail is
used as a middle support for the tape, he must rapidly and lightly tap the underside of the tape to reduce
the friction at the moment of the reading. He must also ensure that the tape is not in contact with weeds,
brush, or other obstructions and that the middle support is not more than 10 centimeters from the middle
mark on the tape at the time of the reading.
The middleman also notifies the recorder of all middle supports marked broken grade. A broken
grade is an intermediate support which is not on grade. If the intermediate support between the tape
ends cannot be placed so that it will be down to grade with the terminal posts, it should be numbered
with colored chalk and marked with a piece of cloth so that it is noticed and touched upon by the level
man. All stakes should be numbered with colored crayon as they are driven. Intermediate supports
above grade should be given a fractional number.
3-8. Run a Baseline. The top of a rail of a railroad track or the surface of a concrete roadway of
uniform grade may be used for baseline measurements. However, these surfaces should not be used
when their temperatures are appreciably different from that of the surrounding air.
a. If the baseline is over uneven ground, provide supports for the tape using substantial posts, 2 by
4 inches or 4 by 4 inches, driven firmly in the ground. To run a baseline, the first task is to set these
posts. Clear the baseline so that the ends are intervisible. Set up the theodolite at one end of the line,
and set the sight (range pole) at the terminating end of the baseline. Carefully adjust the theodolite to
the foresight. Drive the posts on the line, accurately spaced 50 meters between centers. The tops of the
stakes should not be less than 10 inches or more than 24 inches above the surface of the ground and
should be driven to a firm footing. Halfway (25 meters) between terminal posts, drive a 2- by 4-inch
stake. Offset the face of the stake 1 inch from the line of sight. All stakes should be offset on the same
side of the line of sight.
3-7
EN0593
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