Furuno 1830 User Manual

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

Furuno 1830 Specifications

General

Brand	Furuno
Model	1830
Category	Marine Radar
Language	English