course of the survey. It is also desirable to visit field stations and make observations using different instruments in order to
maintain a check of the accuracy of the readings.
h. At the end of the day, or after all the required observations have been made, all altimeters are returned to the
base where the comparison standard altimeter is located. The altimeters are again read simultaneously as they were at
the start of the survey as an added check of the index differences.
During the field survey, any standard level or transit notebook may be used for recording the field notes, or
Wallace and Tiernan Form 1851, or equivalent, may be used (fig. 6).
After the field run has been completed, the field notes are used as a basis for making the final computation.
To make the final computation, a form such as Wallace and Tiernan Form 1925 (shown in fig. 9), may be used.
Computations are made in accordance with the following procedure.
(1) Enter the instrument numbers, upper and lower bases, observers' names, computer's name, checker's
name, date, locality, and state, in the spaces provided in the heading of the form.
(2) Enter the elevation of the lower base, the elevation of the upper base, and the calculated difference in
elevation between those two bases in blocks I, II, and III, respectively.
(3) Enter the station number and the time the reading was taken, in the blocks provided.