a. (1) Enter the date, as in the sample.
b. (2) Enter the time.
c. (3) Enter the name of the observed station and indicate whether the object sighted was a light, a
heliotrope, the top of the instrument stand, the top of the tower, the top of a mountain, the top of a stack,
a tank, a cupola, or spires of intersection stations.
d. (4) Enter the height of light, above or below the monument, at the observed station.
e. (5) Enter the height of the telescope above the monument at the observing station.
f. (6) Compute the difference of heights by subtracting step (4) from step (5).
g. (7) The reduction to line-joining stations is applied to all reciprocal observations and is
computed using the following formula:
The sign of the r value in this column is opposite from the sign of step (6) when zenith distances are
h. (8) Enter the observed zenith distance values directly from the record book.
i. (9) Enter the mean value of the observed angles in step (8). At least three values must be
obtained within a range of 10 seconds.
j. (10) Obtain this value by applying the reduction from step (7) to the mean value in step (9).