Orienteering

Orienteering Skills
Finding Your Way with Map and Compass

A topographic map tells you where things are and how to get to them, whether you're hiking, biking, hunting, fishing, or just interested in the world around you. These maps describe the shape of the land.

They define and locate natural and manmade features like woodlands, waterways, important buildings, and bridges. They show the distance between any two places, and they also show the direction from one point to another.

Distances and directions take a bit of figuring, but the topography and features of the land are easy to determine. The topography is shown by contours. These are imaginary lines that follow the ground surface at a constant elevation: they are usually printed in brown, in two thicknesses.

The heavier lines are called index contours, and are usually marked with numbers that give the height in feet or meters. The contour interval, a set difference in elevation between the brown lines, varies from map to map; its value is given in the margin of each map. Contour lines that are close together represent steep slopes.

Natural and manmade features are represented by colored areas and by a set of standard symbols on all U.S. Geological Survey (USGS) topographic maps. Woodlands, for instance, are shown in a green tint, waterways, in blue.

Buildings may be shown on the map as black squares or outlines. Recent changes in an area may be shown by a purple overprint. A road may be printed in red or black solid or dashed lines, depending on its size and surface.

Orienteering Skills
From Near to Far: Distance
Maps are made to scale; that is, there is a direct relationship, a ratio, between a unit of measurement on the map and the actual distance that same unit of measurement represents on the ground.

If, for instance, 1 inch on the map represents 1 mile (which converts to 63,360 inches) on the ground, the map's scale is 1:63,360.

A convenient way of representing map distance is by the use of a graphic scale bar. Most USGS topographic maps have scale bars in the map margin that represents distances on the map in miles, feet, and kilometers.

Orienteering Skills
From Here to There: Determining Direction
To determine the direction, or bearing, from one point to another, you need a compass as well as a map. Most compasses are marked with the four cardinal points - north, east, south, and west - but some are marked additionally with the number of degrees in a circle (360: north is 0 or 360, east is 90, south is 180, and west is 270). Both kinds are easy to use with a little practice.

One thing to remember is that a compass does not really point to true north, except by coincidence in some areas. The compass needle is attracted by 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. A diagram in the map margin will show the difference (declination) at the center of the map between compass north (magnetic north indicated by the MN symbol) and true north (polar north indicated by the "star" symbol).

This diagram also provides the declination between true north and the orientation of the Universal Transverse Mercator (UTM) grid north (indicated by the GN symbol). The declination diagram is only representational, and true values of the angles of declination should be taken from the numbers rather than from the directional lines.

Because the magnetic declination is computed at the time the map is made, and because the position of magnetic north is constantly changing, the declination factor provided on any given map may not be current. Click here

to find the magnetic declination for your area. **Don't forget to set your magnetic declination on your compass before using it in the field!

courtesy USGS

Orienteering Skills
Taking a compass bearing from a map:

1. Draw a straight line on the map passing through your location and your destination and extending across any one of the map borders.
2. Center the compass where your drawn line intersects the map border, align the compass axis N-S or E-W with the border line, and read on the compass circle the true bearing of your drawn line.

Be careful to get the have your compass pointing in the correct direction (direction of travel) because a straight line will have two values 180 degrees apart. Remember north is 0, east is 90, and so on.

Caution
Compass readings are also affected by the presence of iron and steel objects. Be sure to look out for, and stay away from…pocket knives, belt buckles, railroad tracks, vehicles, electrical lines, radios, battery operated devices, etc.

Navigational Techniques

Deduced (Dead) Reckoning - Straight bearing and distance. Not always the most efficient method, but often unavoidable to some extent.
Orienteering - The ability to read the map and use the terrain features as a travel guide.

Orienteering Methods

Course Navigation
Attack Points
Collecting Features
Catching Features
Aiming Off

Course Navigations

Use compass to point in general direction:
Cardinal points, N, NE, E, SE, S, SW,W, NW
Put compass back in pocket and keep walking in that general direction.
Generally used to walk into large, "can't miss target - like a road.
See Catching features.

Attack Points

A feature that appears on the map that you can positively ID on the ground. Example: Intersections, trail and stream, two roads
Benchmarks
Cemeteries
Distinct Buildings like churches or schools

Attack points are used for confirming positions on a map, or jumping off points to begin Dead Reckoning to target.

Attack points are normally easy to navigate to by orienteering, with little compass work.

Collecting Features

Natural or man-made features that run parallel to your course of travel.
Sometimes referred to as guide rails. - Powerlines, Streams, Ridge lines, Roads, and Trails.
Collecting features allow you to move easily in a constant direction while maintaining a general bearing to your surrounding.
Greatly reduces the burden for Dead Reckoning
Generally used in combination with Catching Features

Catching Features

Natural or man-made feature that crosses your line of travel.
Same type of linear features described in Collecting Features.
Used like way points to measure distance traveled, or as a backstop to prevent over-shooting a target. - (See Aiming Off)

Aiming Off

Normally used on a Dead Reckoning approach over distance.
Requires a catching feature as a backstop.
Purposefully misses the target to one side or the other.
When backstop is reached, navigator knows which direction to turn in order to reach target.

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