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POSITION FIXING WITH RADAR
Position fiving with radar nan he ancurate and nasy once you hncome famiJiar
with
the
different
methods.
The
three
most
common
methods
will
he
discussed in this section.
Take a compass, and a navigation chart to try to
fix your position while revie^A^ing this section.
By Radar Range
The Gimultaneous measurement of the ranges to two or more fixed objecte ie
normally
the
most
accurate
method
of
ohtaining
a fix
with
radar
alone.
Preferably at least three ranges should be used.
However the use of more
than three range arcs may introduce excessive error because of the time lag
between
measurements,
i.e.,
you
will
be
moving
as
you
take
successive
measurements.
When
obtainiiig a fix.
it is best to
measure the most rapidly clianging range
last because of a smaller time lag in the radar plot from the ship's actual
position.
For
greater accuracy.
the objects
selected
should
provide arcs
with
angles
of
cut
as
close
to
90°
as
possible.
Small.
isoJated.
radar-
conspicuous
fixed
objects
whose associated
range
arcs
intersect at angles
approaching
90°
provide
the
most
reliable
and
accurate
position
fixes.
Objects at longer ranges are less accurate for position fixing because they
may be
below
the
radar horizon and because xne widih of tne radar beam
increases with range.
To
fix
your
position,
first,
measure
the
range
to
fwn
or
more
prominent
navigational marks which you can identify on the chart.
(The method for
measuring range is found on page 31.j
Next. with the compass sweep out
the ranges from the charted positions.
The point of intersection of the arcs
is
your
estimated
position.
The
correct
method
of
position
fixing
when
using radar range is illustrated in Fig.45.
Fig.45 Position Fixing Using Radar Ranges
Sy Range and Bearing to a Point of a Land
The advantage of position fixing by range and bearing to a point of land is
the
speed
with
which
a
lix
can
be
obtained.
A
distinct
disadvantage
however is
that
this
method
is
based
upon only two inlersecting
position
lines,
a
bearing
line
and
range,
obtained
from
two
points of
land.
If
possible,
tho
object
URed
should
be
small,
isolated
and
identified
with
reasonable certainty.
To fix your position using range and radar bearing.
45
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