AMCI Basic Mountaineering Course (BMC) 2002

Land Navigation

Orientation is the science of determining your exact position on the earth. It requires mastery of map and compass.

Navigation is the science of determining the location of your objective and keeping yourself pointed in the right direction from your starting point to the destination. Like orientation, this takes map and compass and is a required skill for all wilderness travelers.

Routefinding is the art of locating and following a route that is appropriate to the abilities and equipment of the climbing party. It takes a lot to be a good routefinder: An integrated sense of terrain, distance, and direction; a combination of good judgment, experience, and instinct, and a solid grounding on the technical aspects of orientation and navigation. As with other arts, routefinding skills can be sharpened through practice, regardless of your basic aptitude.

THE MAP

A map is a symbolic picture of a place. In convenient shorthand, it conveys a phenomenal amount of information in a form that is easy to understand and easy to carry.

Topographic Map

There are different types of maps but the best map for backpackers is the topographic or topo. ("Topo" is Greek for place and "graphein" means to write or draw) It depicts topography, the shape of the earth’s surface by showing contour lines that represent constant elevation above sea level.

First, a refresher on how cartographers divide the earth. The distance around our planet is divided into 360 units called degrees. Each degree is divided into 60 units called minutes, each minute is further divided into 60 units called seconds.

A measurement east or west is called a longtitude; a measurement north or south is called a latitude. Longtitude is measure 180 degrees, both east and west, starting at the Greenwich meridian in England. Latitude is measure 90 degrees, both north and south, from the equator.

By determining the intersection of longtitude and latitude lines, any point on the earth’s surface can be pinpointed.

On a map, a latitude of 48 degrees, 53 minutes, and 2 seconds north would be written as 48 degrees 53’ 23’’ N.

The kind of topo map used by mountaineers covers an area of 15 minutes (that is ¼ degree) of longtitude by 15 minutes of latitude.

Parts of a Topographic Map

MAP NAME. It is found at the central upper portion of the map. The map name is taken from the most prominent feature on the map (usually the biggest town or city).

MAP SCALE. It is a fraction or ratio of the distance measured on the map compared with the actual distance on the ground. The scale for a 15 minute topo map is 1:50,000 which means one centimeter of the map equals 50,000 cm or 500 m on the ground.

Distance on a map is done by linear measurement. This means aerial distance, the measured distance between two points on a flat surface. Actual distance is longer because of the ruggedness of the terrain.

SHEET NUMBER. Maps are numbered in sequence with adjacent maps.

LEGEND. A glossary of symbols found on the map.

MAGNETIC DECLINATION. It shows the difference in degrees between the direction of true north (geographical north) and magnetic north in the region.

CONTOUR INTERVAL NOTE. Indicates the difference in elevation between two adjacent contour lines.

INDEX TO BOUNDARIES. Indicates the political boundaries present in the map.

INDEX TO ADJOINING SHEETS. Indicates the sheet number of adjacent maps.

LONGTITUDE AND LATITUDE. Designations found at the four corners of the map. It indicates the exact longtitude and latitude for that particular corner of the map. All corners have this.

CONTOUR LINES. These are brown, squiggly lines which give us an idea of the profile of the land. A single contour line connects points of the same elevation.

COLOR. Each color in a map conveys something so that the feature may be recognized at once.

GRID LINES. These are the north-south lines and the east-west lines of the map. The term grid north applies to the direction from the bottom of the map to the top, along the north-south lines.

Using a Topographic Map

Determining distance is one of the uses of the map. To do this you must first know the scale of the map. The scale most often used for mountaineering is 1:50,000 since it covers a lot of ground (26 kilometers across) but still gives detailed information on land features.

On a 1:50,000 map, it is worthwhile to remember that:

MAP		GROUND
1 mm		50 meters
1 cm		500 meters
2 cm		1,000 meters (1 km)

Memorize these simple figures so that you can use the millimeter or centimeter scale on the compass for measurement instead of the distance scale on the map which is often tucked out of the way when the map is being used on the field.

Recognizing landscape is one of the most important skills a mountaineer must acquire. The following listing shows the main features sketched by contour lines.

• Flat areas. No contour lines at all.
• Gentle slopes. Widely spaced contour lines.
• Steep slopes. Closely spaced contour lines.
• Cliffs. Contour lines extremely close together or touching.
• Valleys, ravines, gullies or couliors. Contour lines in a U pattern in the direction of higher elevation if the valley or gully is gentle or rounded; a V pattern for a sharp and narrow valley or gully.
• Ridge or spur. Contour lines in a U pattern pointing in the direction of lower elevation if the ridge is gentle and rounded; a V pattern for a sharp and narrow ridge.
• Saddle, pass, col. A low point on a ridge, with higher contour lines on each side and often with a characteristic hourglass shape.
• Cirques, bowls. Patterns of contour lines forming a semicircle, rising from a low spot in the center of the partial circle to form a natural amphitheater at the head of a valley.
• Peak. A concentric pattern of contour lines with the summit being the innermost and highest ring. Peaks often are also indicated by X marks, elevation bench marks, or a triangle symbol.

Compass

The best kind of compass for land navigation is called a protractor or, more commonly, a baseplate compass.

Parts of a Baseplate Compass

• baseplate – a rectangular piece of clear plastic
• direction of travel arrow
• index mark -
• gate
• capsule – houses the compass needle; it is graduated from 0 degrees to 360 degrees in 1 degree increments; it can be rotated in relation to the baseplate
• needle – rotates freely inside the capsule filled with viscous liquid which damps the its swing; its north end points to magnetic north

Getting a Bearing

Setting a Bearing