following equipment:
A surveyor's umbrella to shade the instrument.
Turning pins or plates to set the rod on during observation.
Hammers to set the turning pins.
A locator's hand level to estimate the lines of sight.
Hand-held counters to tally paces for the approximate balancing of the lines of sight.
Recording books and conversion tables for note keeping.
4-8. Field Tests and Adjustments. To maintain the required accuracy, certain tests and adjustments
must be made before and after the level is used.
a. Determine the Stadia Constant. Carefully determine the stadia constant of the instrument before
it is used. It is the factor by which the totals of the cumulative sums of the total intervals for both
backsights and foresights are multiplied to obtain the lengths of the sections. These results, in turn, are
used in the formulas for computing the allowable divergences (errors) between the forward and
backward runnings of the various sections. Comparing the stadia intervals observed over a known
course will aid in the determination.
(1) Select a suitable stretch or reasonably level track, roadway, or sidewalk. Place nails or other
marks in a straight line at distances 75, 85, 95, 105, 115, and 125 meters from an initial-point 0.2 meter
to the back of the center of the N-3 level. Using the direct method, read the three thread readings on the
rod at each of these stations, and record the readings on a DA Form 5820, as shown in Figure 4-5. The
split-level bubble of the N-3 need not be accurately centered for these readings, but it should be free of
the ends of the tube. Compute the half-thread intervals as a check against erroneous readings, and
compute the sum of the total intervals for the six readings. The stadia constant is the sum of the
measured distances (300 meters) divided by the sum of the six total thread intervals (300 - 898 = 0.334).
EN0593
4-10
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