The document discusses various methods for obtaining lines of position (LOPs) and fixes to determine a ship's location, including visual bearings, radar ranges, and coincidental or intentional ranges. It provides guidelines for best practices such as choosing navigational aids to provide an optimal spread of LOPs, determining the order of plotting LOPs, and the appropriate frequency of obtaining fixes based on proximity to hazards.

1. 1000 Light NS100 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 15 17 17 17 17 19 19 19 19 Fundamentals of Naval Science Lines of Position & Fixes

2. Lines of Position (LOP’s) LOP - A single observation that does not establish a fix but does mean the ship’s position is somewhere along that line. Label - a four digit time must be written above and parallel to the LOP.

3. Lines of Position (LOP’s) Visual LOP “shooting” tanks, water towers, church steeples, spires, radio and TV towers, daymarks, fixed navigation lights, flagpoles, or tangents to points of land.

4. Single LOP Tank

5. Light 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 15 17 17 17 17 19 19 19 19

6. 1000 Light Visual LOP 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 15 17 17 17 17 19 19 19 19

7. TWR Visual Bearing LOP 2357 2246 Radar Range LOP

8. Light Radar Range LOP 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 15 17 17 17 17 19 19 19 19 1500

9. Lines of Position (LOP) Visual Range - The most accurate type of LOP , when two known objects line up. Some ranges are man made: “intentional” and others are natural: “coincidental.”

10. COINCIDENTAL RANGE

11. INTENTIONAL RANGE

13. Lines of Position (LOP’s) Visual Bearing can be measured in: - Degrees Relative ( # # # o R ) - Degrees per Gyro Compass ( # # # o pg c ) - Degrees Magnetic ( # # # o pstgc or o M ) - Degrees True ( # # # o T ) The navigator must convert any of these types of bearings to True before they can be plotted on the chart.

14. 0815 0835 0900 Range Tangent Bearing Distance Arcs 0915 Tank

15. Plotting and Labeling a Fix Fix - The point where two or more LOP’s cross. This indicates the ship’s 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.

16. Using 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 .

17. SPIRE TWR TANK 1036 1145 wk Visual Fix

18. 12 6 6 6 6 12 12 12 Tank Electronic Fix TWR

19. Symbol Type Meaning Labeling Fixes Fix Fix DR EP Accurate Visual Fix Accurate Fix obtained by electronic means Dead reckon ing position, advanced from previous fix. Estimated position. Most probable position of ship.

20. TR Visual Fix 1145

21. TR Electronic Fix 1843

22. Optimum Spread of LOP’s Best Fix – LOP’s must be widely spaced, two LOP’s at nearly the same angle will be less accurate. Formula – Both sides: 360 0 / number LOP’s – One side: 180 0 / number LOP’s Example: There are three LOP’s then optimum separation is 120 0 . Same side: 60 0 .

23. “ 2” Fl R 4 sec 1412 Visual Fix Tank TWR

24. TWR TANK LT 60 60 0930 Visual Fix

25. Determining the Order of LOP’s Bearings LOP’s Shoot Bearings: “Beam to Bow” Range LOP’s Shoot Ranges: “Bow to Beam”

26. Navigational Aid Selection Choose Nav Aids based on: - Provides the best bearing spread. - Lighted so that navaids can be used in low visibility and day or night. - Easily distinguishable by bearing takers.

27. 1000 Light Visual FIX 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 15 17 17 17 17 19 19 19 19

28. Light Electronic Fix 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 15 17 17 17 17 19 19 19 19 1015

29. 11 15 1000 Light Accurate / Inaccurate fix 9 9 9 9 9 9 9 9 9 9 9 5 5 5 5 11 11 11 11 11 11 11 6 pa FL 6s 58ft 9M Tank Long Point 20 20 20 20 20 20 21 20 20 20 21 21 21 21 21 21 23 23 23 23 23 23 15 15 15 17 17 17 17 19 19 19 19 1015