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Contents

1. Training strategy
2. Maps
3. Marginal information and symbols
4. Grids
5. Scale and distance
6. Direction
  - Methods of expressing direction
  - Base lines
  - Azimuths
  - Grid azimuths
  - Protractor
  - Declination diagram
  - Intersection
  - Resection
  - Modified resection
  - Polar coordinates
7. Overlays
8. Aerial photographs
9. Navigation equipment and methods
10. Elevation and relief
11. Terrain association
12. Mounted land navigation
13. Navigation in different types of terrain
14. Unit sustainment

A. Field sketching
B. Map folding techniques
C. Units of measure and conversion factors
D. Joint operations graphics
E. Exportable training material
F. Orienteering
G. M2 compass
H. Additional aids
I. Foreign maps
J. Global positioning system
K. Precision lightweight global positioning system receiver

Survival Gear

Handheld GPS
Specialty Outdoor Gear
Digital Compasses
Survival Books
Hunting and Fishing Magazines

6-2. BASE LINES

In order to measure something, there must always be a starting point or zero measurement. To express direction as a unit of angular measure, there must be a starting point or zero measure and a point of reference These two points designate the base or reference line. There are three base lines— true north, magnetic north, and grid north. The most commonly used are magnetic and grid.

a.   True North. A line from any point on the earth's surface to the north pole. All lines of longitude are true north lines. True north is usually represented by a star (Figure 6-1).

Figure 6-1. Three norths.

Figure 6-1. Three norths.

b.   Magnetic North. The direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument. The magnetic north is usually symbolized by a line ending with half of an arrowhead (Figure 6-1). Magnetic readings are obtained with magnetic instruments, such as lensatic and M2 compasses.

c.   Grid North. The north that is established by using the vertical grid lines on the map. Grid north may be symbolized by the letters GN or the letter "y" (Figure 6-1).



Direction
Methods of expressing direction | Base lines | Azimuths | Grid azimuths | Protractor | Declination diagram | Intersection | Resection | Modified resection | Polar coordinates |




Buy The Book This Site Is Based On
The 'Land Navigation' section of this site is based on 'Map Reading and Land Navigation', a public domain work published by the U.S. Department of Defense that is available for sale at Amazon.com.




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