Map and Compass

Troop 118 St. Stephen United Methodist Church

Charlotte, NC 28270

Page 1

Table of Contents

Overview .......................................................................................................................... 2

Identifying the Parts of the Compass ............................................................................ 2

Topography Map Legends ............................................................................................. 3

Topography Maps and Contour Lines ........................................................................... 4

Topography Map Colors & Features.......................................................................... 4-5

Using a Compass to Orient a Map ................................................................................. 6

Finding / Reading Directional Bearings ........................................................................ 6

Determining Distance ..................................................................................................... 7

What is Declination? ....................................................................................................... 7

Page 2

Overview This purpose of these materials is to use them as an instructional aide to explain how to read a topography map and use a compass. We’ll start first with the compass, then the map, and finally, how to use them together. The goal is for Scouts to master these skills and be able to effectively navigate and find their way outdoors with a map and compass.

Identifying the Parts of the Compass

The parts of the compass are:

Baseplate – plastic plate that everything is attached to

Compass Housing – is the ring with 360º inscribed onto it

Orienting Arrow – the arrow on the Compass Housing used to align the compass with the map or Magnetic North. We also call this the “SHED”

Orienting Lines – lines used to align the Compass Housing with the map or Magnetic North. These are parallel to the Orienting Arrow.

Bearing Mark – the mark showing the direction of travel measured in degrees.

Direction of Travel (arrow) – The line pointing to your destination if you travel at the bearing shown on the Bearing Mark. This line points to your destination.

Compass Needle – the floating needle pointing toward Magnetic North.

Scale(s) – are calibrated markings used to measure distances on maps.

Page 3

Topography Map Legends

The map legend contains a number of important details. The pictures that follow show sections of a standard USGS topo map legend. Here are the major details found on a map legend:

1. Map Name 2. Year of Production and Revision 3. General Location in State 4. Next Adjacent Quadrangle Map 5. Map Scale 6. Distance Scale 7. Contour Interval 8. Magnetic Declination 9. Latitude and Longitude

Page 4

Topography Maps and Contour Lines

A topographic map is a two-dimensional representation of the three-dimensional world. The sense of the three dimensions is portrayed through the use of contour lines, which are drawn with brown ink. Each contour line represents a specific elevation above sea level. The amount of vertical distance between adjacent lines is indicated in the map margin as that map’s contour interval. Other notes on contour lines:

- Each contour line represents one elevation - Every fifth contour is printed in darker brown. These lines are called index contours. - If you follow a dark brown index contour line you will likely find it’s elevation listed - Closely spaced contour lines represent steep slopes - Widely spaced contour lines represent gentle slopes - Maps with few contour lines signify relatively flat territory - Contour lines never cross - A series of contentric contour lines in a rough circle represents a hill.

Topography Map Colors & Features

Blue = Water features (ocean, lakes, streams) Green = Vegetation, usually forest White = Land such as meadows with no tall vegetation Brown = Contour lines Black = Anything that is man-made (buildings, place names, boundary lines) Red = Principal roads Pink = Urban areas Purple = Revisions to an older map

Look at the topo map of the Birkhead Mountains Wilderness and pick out the features and symbols.

Page 5

Page 6

Using a Compass to Orient a Map

1. Set the compass housing so that N (north) or 360º on the dial is aligned with the direction of travel line.

2. Lay the compass on the map so that its long edge is aligned with the map edge or one of the vertical map grid lines.

3. Rotate the map and compass together until the needle (RED) is centered in the orienting arrow (SHED) as. Remember red in the shed.

Finding / Reading Directional Bearings Once you orient your map, you can plot your course from your current location to another location on the map by:

1. Without moving the map, use the edge of your compass to connect a line between the starting point and ending point.

2. Turn the compass housing until RED is in the SHED 3. Look at the compass housing. Where the compass housing intersects with the line for

the direction of travel, what is the “Reading” in degrees?

Page 7

Determining Distance A compass bearing can point you in the direction you wish to travel but it can’t tell you how far along that route you will need to go in order to reach your destination. For that, you can refer to the distance rulers in the map’s margin

1. Place one end of a piece of string on the map at your starting point. 2. Lay out the string on top of the route you plan to use 3. Bend the string to conform to the twists and turn of the route 4. Pinch the string where it touches the map symbol for your destination 5. Pick up the string and stretch it over the bar scale in the bottom map margin. Measure

to the point that you are pinching. That’s the approximate length of your route

What is Declination? Magnetic North It is very important to remember that a compass does not really point to true north, except by coincidence in some areas. The compass needle is attracted by the Earth’s magnetic force, which varies in different parts of the world (and is constantly changing). When you read north on a compass, you're really reading the direction of the magnetic north pole. All bearings given by a compass are with respect to magnetic north. Declination The difference between magnetic north and true north is called the declination or declination correction. Just as all compasses read in magnetic degrees, most maps are drawn with true north as up and include the legend for True North and Magnetic North like these pictures:

EAST DECLINATION WEST DECLINATION

In the first example, Magnetic North is EAST or to the right of True North and is known as EAST Declination. In the second example, Magnetic North is WEST or to left of True North, and is known as WEST Declination How to Correct for Declination There are several methods to correct for declination and it takes quite a bit of time to review. This will be covered another time. But familiarize yourself with the definitions of True North, Magnetic North and declination using the explanation and pictures above.