AGENDA:

1
Lesson 6 Lines of Position Fixes

• AGENDA
• Visual and Radar Lines of Position
• Plotting Visual and Electronic Fixes
• Selecting a Navigation Aid
• Resolving Fix Ambiguity

2
Lines of Position (LOPs)
LOP - A plotted line on which a vessel is
located. A visual LOP can be taken, or shot,
using fixed navigational aids such as tanks,
water towers, church steeples, spires, radio and
TV towers, daymarkers, fixed navigation lights,
flagpoles, or tangents to points of land.
3
Tank
Visual LOP
Light
FL 6s 58ft 9M
Long
9
Point
9
5
5
9
5
9
9
9
9
11
5
11
9
9
11
11
15
11
11
15
15
9
11
15
17
19
pa
17
19
19
9
6
17
17
19
11
20
20
20
20
21
20
20
20
20
21
21
20
1000
21
21
21
23
23
23
23
23
4
Tank
Radar Range LOP
Light
FL 6s 58ft 9M
Long
9
Point
9
5
5
9
5
9
9
9
9
11
5
11
9
9
11
11
15
11
11
15
15
9
11
15
17
19
pa
17
19
19
9
6
17
17
19
11
1500
20
20
20
20
21
20
20
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21
20
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5
Tangent LOP
070
0635
6
Visual Ranges

• Visual Range - The most accurate type of LOP,
  when two known objects line up.
• Some ranges are man made, intentional others
  are natural, coincidental.

7
INTENTIONAL RANGE
COINCIDENTAL RANGE
8
Plotting and Labeling a Fix
Fix - The point where two or more LOPs
cross. This indicates the
ships position on the chart. Label -
Use the four digit time next to the fix,
it should be parallel to the bottom of
the chart. The times of the individual LOPs
are not written on each LOP.
9
Tank
Visual Fix
Light
FL 6s 58ft 9M
Long
9
Point
9
5
5
9
5
9
9
9
9
11
5
11
9
9
11
11
15
11
11
15
15
9
11
15
17
19
pa
17
19
19
9
6
17
17
19
11
20
20
20
20
21
20
20
20
20
21
21
20
1000
21
21
21
21
23
23
23
23
23
23
10
6
6
6
12
12
12
Tank
6
Electronic Fix
12
11
Labeling Fixes
Symbol Type Meaning
Fix Fix DR EP
Accurate Visual Fix
Accurate Fix obtained by electronic means
Dead reckon position, advanced from previous fix.
Estimated position. Most probable position of
ship.
12
Tank
Light
FL 6s 58ft 9M
Long
9
Point
9
5
5
9
5
9
9
9
9
11
5
11
9
9
11
11
15
11
11
15
15
9
11
15
17
19
pa
17
19
19
9
6
17
17
19
1503
11
20
20
C 090º
C 090º
S 10
20
20
21
1506
20
20
20
21
21
1503
1506
20
S 10
21
1500
21
21
21
23
23
23
23
23
23
R FL 2s 38ft 10M
13
The Centroid Concept
Problem - If a large triangle is formed by a 3
LOP fix, mark the center of the triangle as
the fix. Danger - If the large triangle is near
a hazard then choose the part of the
triangle closest to the hazard.
14
SPIRE
TWR
TANK
1145
wk
Labeling Visual Fixes (Centroid Concept)
1036
15
Optimum Spread of LOPs
Best Fix - LOPs must be widely spaced, two
LOPs at nearly the same angle will be less
accurate. Formula - 3600 / number of
LOPs Example There are three LOPs then
optimum separation is 1200.
16
Visual Fix
0930
60
60
LT
TWR
TANK
17
TWR
SPIRE
90
1036
1039
TANK
Visual Fix
18
Determining the Sequence of Shooting LOPs
Bearings LOPs - Shoot visual bearings
that are on the beam first because they
change the fastest. Shoot Bearings
Beam to Bow Range LOPs - Shoot radar ranges
on the bow/stern first because their
range changes fastest. Shoot Ranges Bow to
Beam
19
Navigational Aid Selection
Choose Nav Aids based on - Provides the best
bearing spread. - Lighted so that Nav Aids can
be used in low visibility and day or
night. - Easily distinguishable by bearing
takers. Example Which radio tower?
20
REVIEW
1. What are the two types of LOPs ? 2. How do
you label a single LOP ? 3. The most accurate
type of LOP is called? 4. Name three ways visual
bearings can be measured? And what must
they be converted to in order to plot them
on the chart? 5. Explain how to choose the
centroid of a triangle from a poor fix?
21
HOMEWORK

• Using chart 12245 plot and label the following
  visual aids
• A) 36 57 14 N
• 76 19 37 W
• B) 36 55 54.5 N
• 76 19 44 W
• C) 36 56 42 N
• 76 18 36 W
• DO NOT ERASE THESE MARKS!!

22
HOMEWORK

• Using chart 12245 and the visual aids plotted on
  the previous slide, use the bearings below from
  your ship to determine your position
• A) 018T
• B) 166T
• C) 078T
• DO NOT ERASE THESE MARKS!!

23
2357
Visual Bearing LOP
TWR
Radar Range LOP
2246
24
TR
Visual Fix
25
TR
Electronic Fix
26
TR
Range
Electronic Fix
27
Tank
Light
FL 6s 58ft 9M
Long
9
Point
9
5
5
9
5
9
9
9
9
11
5
11
9
9
11
11
15
11
11
15
15
9
11
15
17
19
pa
17
19
19
9
6
17
17
19
11
??
20
20
1500
20
20
21
20
20
R FL 2s 38ft 10M
20
20
21
21
20
21
21
21
21
23
23
23
23
23
23
28
Visual Fix
2 Fl R 4 sec
1412
29
Tank
Electronic Fix
Light
FL 6s 58ft 9M
Long
9
Point
9
5
5
9
5
9
9
9
9
11
5
11
9
9
11
11
15
11
11
15
15
9
11
15
17
19
pa
17
19
19
9
6
17
17
19
11
20
20
20
20
21
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20
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1015
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31
INTENTIONAL RANGE
32
Tank
0733
Visual Fix
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34
0835
0815 LOP
Range
Bearing
0915
0900
Distance Arcs
Tangent