29-B
97MU001-F
ANTHEA OPERATION AND INSTALLATION MANUAL
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Tr and T1 are not identical, since the beginning and the end of each of these timings are
not identical.
If the base distance is long enough to be able to accept an approximation of a tenth of a
mile, just not the indications on the distance counter upon entering and leaving the base
distance zone.
The above measurements are to be taken over several runs.
a) When in a zone where the current remains constant throughout the tests, the base
distance zone should be covered a second time in the opposite direction, carrying out the
same operations. The average of the speeds obtained is then calculated :
V average
=
V1 + V2
2
b) If the current is not constant, a third run in the same direction as the first will be made,
as long as the tests are made consecutively with no time out between any two test runs.
The average is calculated as follows:
V average = V1 + 2V2 + V3
4
V1 = speed calculated on the first run
V2 = speed calculated on the second run
V3 = speed calculated on the third run
Always try to operate at the speed given by the log, modifying the engine speed controls
if necessary.
Do not perform the measurements while the tide is turning.
Having found the average real speeds and the average log speeds, a simple calculation
will provide the percentage of error of the log.
The percent error is: 100 x (V1 – VR)/V1
This error may be positive or negative.
Example: suppose that 1.1 miles are covered in a clocked time of Tr1 = 364 seconds.
