Using the Fathometer
Charted landmarks on the ocean floor are often useful in assisting
mariners in determining their position. Submarine trenches, canyons,
ridges, and seamounts can all be useful in navigation. Echo-sounding
equipment such as the Navy AN/UQN-4 is the most common fathometer
found on naval vessels. This fathometer is the most accurate for
obtaining soundings in shallow depths. The AN/UQN-4 can be set for
five different scales. It is equipped with a digital display for reading all
scales and it has a strip chart recorder that actually traces the profile of
the ocean bottom when reading the 600-foot, 600-fathom, or
6,000-fathom scale. The smallest possible scale should always be used.
See figure 8-26.
Figure 8-26. Fathometer, transducer, and echogram.
The paper on which the depths are recorded is used to annotate the
following information at the times indicated:
The ships name must be placed at the beginning and at the end of
each roll of paper.
Time in GMT must be marked at the beginning of each watch.
The current date should be recorded each day at 1200.
Time and date must also be marked whenever the unit is turned on.