2.2.2
Location Procedures
The location of the ship was determined with the assistance of
four types of equipment. For the most part they represent independent
methods. The equipments were:
:
{3}
2)
Raydist, an electronic navigation device
Sextants
(4)
Taut wire equipment
(3) Alidades combined with a gyrocompass Mk. 18
The ‘Raydist principle is that the distance between two points
can be measured by counting the number of standing radio waves between
the two poiats. More specifically the difference in radius from two
shore points is. determined by measuring the difference in the number of
standing waves; In the actual equipment this is accomplished by measuring the phase of a 400-cycle beat note at three fixed receiving stations. This:beat note is produced by transmitters of approximately 12.5
me, one of which is fixed and the other on the ship being tracked.
The Raydist; equipment as actually used involved installations
requiring 60-cycle: power at each of four shore points.
Each of these
shore installations had a transmitter and three of them had receivers
in addition.
On shipboard: the installation, which of course required
an additional source of &-cycle power, was comprised of three recei-
vers, a transmitter, and;equipment for the phase comparison.
While Raydist equipment, ‘permitted the determination of the ship's
position easily to within 20 ft,it had the limitation that the ship's
location was determined only relative to some fixed point where the
ship must have been.
This fact-‘combined with the fact as noted that
five sources of @e«cycle power were‘required (four on shore at isolated
locations and one on the ship) proved; to be one of the major headaches
in the actual operation of the equipment, since if any of the five power
supplies failed, it was necessary to reqest the run and return the ship
to the known starting point.
The sextants used were standard hety issue except that they could
be read to 10 sec. The general limitations onthe use of sextants were
found to be very extensive, since three well defined shore points whose
location is known are required and the strengthof the fix approaches
zero as the ship approaches the circle determined by the three shore
points. There is the further limitation thatif very distant shore
points are used, then even the full angular accuracy of tre sextants
results in relatively poor absolute precision of the fix. Finally, the
capability for finding and retaining ill-defined objects--with the sex-
tants was mich poorer than with the alidades. For these various reasons, in practice the sextants were used only as a backup‘Procedure for
locating the ship and were used only occasionally.
:
A gyrocompass Mk. 18 was installed on the boat for “the:use of
this project, and two repeaters, one on the flying bridge and the other
on the forward starboard 40 mm gun mount, were installed.
These re-
peaters were complete with alidades having a magnification of about
2.5. In practice the alidades and gyrocompass proved to constitute the
pest method of positioning the ship and this equipment was used either
20