d.
When recording altimeter readings, read the dial in accordance with the instructions described in paragraph
e. The same points shouL11 be visited twice if practicable. These successive visits will provide a mean value
which in most cases will be more accurate than any single reading. Revisits should not be closer together than one hour
for each point, and the time interval should be longer, if convenient.
f.
It is desirable that one or more known elevations (other than the base stations) be included in each line of
altimeter points to be run.
g. When running a new altimeter line adjacent to a previously completed line, one or more of the points of the
old line should be included in the new line. This use of common points will provide an indication of the consistency of the
final results. Also, the use of these points will provide additional values which can be used to determine the final mean
result of the common point or points.
17.
Precautions
The following general precautions and/or limitations should be observed whenever possible.
a. Observe station and field altimeters under similar conditions outdoors, but protect them from sun and strong
winds. Between stations keep the altimeter shaded.
b. Cushion the altimeter against road shock, and avoid sudden jarring at all times.
c. Avoid midday observations. Best results may be obtained following the recommended observation periods
described in paragraph 16a.
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