1o Terms You Need to Know about Navigation
Here are 10 terms that you need to know to understand Navigation by map and compass.
They are not the only ones, but they are an important ten that you have to understand to move forward and feel comfortable in your study of Navigation.
As in all branches of study, no one aspect of any subject is more important than any other. These terms are presented in no specific order and are all important to the study of the Map and Compass.
The whole is always a sum of its parts and this concept applies to Navigation as well.
1) True North … True North is also known as Geographic North. This is at the top of your map. Lines of longitude run in a north – south direction.
These vertical lines describe the left and right margins and are the true meridians.
These meridians converge towards the poles, and although they appear to be parallel on your map, the closer you get to the poles, the less parallel they become.
2) Grid North … All topographic maps have grid lines on them.
The vertical grid lines are the lines of longitude. These lines are the true meridians.
They are now parallel lines on your map because the “round” Earth has been placed on a flat surface.
3) Magnetic North … Your compass needle does not point to true north.
It points to magnetic north, which is located several hundred miles south of the real thing.
4) Latitude … Lines of latitude are the horizontal lines on your map or globe.
These lines are always parallel and are measured in degrees North and South of the Equator.
The Equator is 0° and 90° at the North and South poles.
The latitude of the North Pole is 90° N, and the latitude of the South Pole is 90° S.
5) Longitude … This is the distance in degrees east or west of the Prime Meridian which passes through Greenwich, England.
These lines of longitude are known as Meridians and run True North and South.
Longitude is also expressed in degrees ranging from 0° at the Greenwich or Prime Meridian to 180° east and west.
6) Contour Lines … These are the light brown lines on your topographic map and they indicate elevation above mean sea level.
From these contour lines you can see the valleys and hills on your map area.
The closer the lines are the steeper the area.
When the contour lines are further apart the land area is much flatter.
7) Declination … This is the angular distance measured in degrees East or West of True North.
It is the angle in degrees, between True North and Magnetic North.
This angle varies depending on your position on the Earth’s surface and also varies with time.
All topographic maps have a declination value diagram. This will indicate the Year and the Annual Change increasing or decreasing, expressed in degrees.
8) Bearing … A bearing is a direction in degrees on the compass circle, from where you are standing to where you are going.
It is the reading in degrees east or west of a north-south reference line.
A bearing will be expressed as North or South and includes an angle value which is always less than 90°.
For example, if Point B is located exactly southwest of Point A, the bearing from Point A to Point B is S 45° W.
9) Scale … This is the relationship between the distance on the ground and the distance on the map.
It can be expressed as 1: 125 000.
This means that 1 centimeter=1.25 kilometers.
10) Inclination … The Earth is a gigantic magnet and the closer you get to the poles the greater this magnetic force is. This increase in magnetic force affects the compass needle.
For instance, in the Northern Hemisphere this causes the North end of the compass needle to tip down and it causes it to rise in the Southern Hemisphere.
This is why professional compasses have NH, SH, or Global designations.
Your compass needle has to be balanced for the zone of operation you will be using it in so that the compass needle can spin freely on its pivot.
These are only 10 terms that form part of the language of Navigation.
The field of navigation is divided into four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation.
In the broader sense, Navigation is the skill of determining position and direction.
If you have any comments, questions, or suggestions, please do not hesitate to drop by and express them below.
What is the most difficult part of navigation for you to understand and how could I shed some light on it for you?