best to prorate the adjustment through the intermedate new points, according to elevation. If the ties are
at nearly the same elevation, prorating according to time, distance, or locality, may be the best method.
However, this is left to the computer's judgment.
Note.
In order to eliminate computations when employing the two-base method of altimetry, a
Wallace and Tiernan Palmer Altirule, or equivalent, may be used. This device permits a direct
calculation of elevation.
20.
Leapfrog Method of Altimetry
In the application of the leapfrog method of altimetry, the same corrections for temperature and relative humidity
are required as for the single-base method previously described. However, the observational methods differ, and are as
follows:
a. Two altimeters (A and B, fig. 10) are read simultaneously at the base station. After this initial reading,
altimeter A remains at the base station, and altimeter B advances to the first field station.
b. After altimeter B advances, the two instruments are read simultaneously. The appropriate correction factors
for temperature and relative humidity are applied, and the difference in the two readings gives the correct elevation for the
first field station.
c. Next, altimeter A leaves the base station and leapfrogs the first field station, advancing to the second field
station. During this period, altimeter
34