b. Sight along the tops of both of the 50-meter posts and locate and drive a fiducial nail horizontally
into the face of the intermediate stake so that the nail is on line with the tops of the posts. These nails
serve as intermediate supports between 50-meter posts during measurements. Nail a strip of copper or
zinc on top of the 50-meter posts to provide a suitable surface on which to mark the tape lengths.
c. Ideal conditions may not be present in actual field practice. For example, at ravines and streams,
it may be necessary to begin a tape length by placing a stake on the edge of a bank. If this stake is less
than half a tape length from the previous tape end post, the number of which is 16, number the
fractional-length post 16 setup. Number the next terminal post 17. If the fractional-length post is more
than half a tape length from the next preceding tape end post, drive a 2- by 4-inch stake at the halfway
mark and number it 16 1/2 setup. Following this system will prevent uncertainty in the interpretation of
the records.
d. With the reconnaissance made, the signal towers erected, and the station stakes set, it is time to
measure the exact length of the baseline. Before doing this, run a line of levels over the line to
determine the relative elevations of all 50-meter posts and broken-grade stakes.
when using a rod graduated in meters on one side and feet on the other. When using such a rod, run the
levels only in one direction, but read both sides of the rod at each rod point. Record the reading in
meters as the forward running and the reading in feet as the backward running. If the rod is graduated
on only one side, make both forward and backward runnings. Be extremely careful to obtain readings
on all broken grades and partial tape lengths, and plainly indicate the readings in the record. Mark the
columns as either meters or feet, as applicable. Pay particular attention to the column headings in the
level notes. Each item will eventually enter into the final calculations for the true length of the baseline.
Refer to Figure 3-2 and the following information for required detailed column information:
EN0593
3-8
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