All truths are easy to understand once they are discovered; the point is to discover them. - Galileo Galilei


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Altimeter: An instrument that measures elevation by using barometric (air) pressure.

Azimuth: same as bearing. Refers to the degree of bearing from your current position to a landmark or destination. Reversing the bearing would be known as a back azimuth or back bearing.

Azimuth Ring: See Housing.


Back bearing: the 180-degree opposite of the azimuth or bearing. Also known as back azimuth.

Back sighting: what you do when you are establishing a back bearing.

Baseplate: the see-through plate of an orienting compass onto which the compass housing is mounted.

Berm: A lip or edge of debris that builds up on the downhill side of a trail preventing water from flowing off the trail and leaving a puddle or muddy area to form.

Bearing: the direction of travel from your current position to a landmark or destination expressed in degrees from 1 to 360. Same as azimuth.

Bench mark: a permanent (as permanent as things can be in this world) object that is either natural or man-made with a known elevation that can be used as a reference point when navigating.

Bezel(Flashlight):front part of light that often includes flashlight lens, reflector, and bulb.

Blaze: a trail marking that can be either a painted symbol on a tree, a sign or a rock cairn.

Box canyon: a canyon that is surrounded on three side with an entrance but no separate exit.

Boxing the needle: a term that refers to placing the red end of the magnetic needle exactly over the red end of the orienting arrow when determining a bearing. Since the orienting arrow is slightly larger than the magnetic needle, we refer to having "boxed" the magnetic needle in. Some books or manuals will refer to this as "red on red" or "centering" the needle.

Buffer zone: a protective strip of land on either side of a trail or waterway that insulates the wilderness traveler from development, mining or logging.


Cache: a placement of food and / or supplies along or near a trail or route of travel for future use.

Cairn: a stack or mound of stones that provides a visible marker of a trail's location through areas that are devoid of trees.

Cardinal points: the four main points of direction on a compass- North / 360 degrees; East / 90 degrees; South / 180 degrees; and West / 270 degrees.

Clinometer: a feature found on some compasses that allows the compass to measure vertical angles (such as the slope of a hill). Clinometers can also be used as a level.

Col: a pass between two peaks or a gap in a ridge line.

Contour interval: the difference in elevation (height) between one contour line and the next. This interval is either expressed in feet or meters.

Contour line: Each contour line comprises an often irregular closed loop that connects points of equal elevation. The line with a darker shade of brown, typically every fifth line, is called an index contour and usually has the elevation printed on it. Elevations refer to elevation above sea level.

Coordinate: GPS (Global Positioning System) rely on coordinates which are nothing more than a series of numbers that indicate on which map and in which grid the position displayed is located. Latitude and longitude and UTM eastings and northings are nothing more than coordinates on a grid.

CR123: the most common size of 3v lithium disposable battery because of their tremendous weight to power ratio.


Declination: the difference in degrees between magnetic north (the direction the magnetic needle on a compass points) and true or geographic north (the direction maps are printed towards).

Depression: a natural or man-made hole in the ground which may or may not have a wet bottom. Depressions are shown on topographic maps by a contour line with small hachure marks pointing inward.

Direction-of-travel arrow: the arrow engraved or painted onto the front of the baseplate of the compass that is designed to indicate the direction you should hike when a bearing has been established or the direction you should point the compass to establish a bearing.

Double blaze: two painted blazes or markings on a tree that announce a change in direction or junction along a trail.


EVA n: Short for Expanded Vinyl Acetate. This is the closed-cell foam in the midsole of many athletic, trail running and hiking shoes. EVA is used for its cushioning qualities since it is lighter and softer than the other major midsole ingredient -- polyurethane, or PU.


Freshet: a sudden overflow of a stream caused by heavy rain or nearby thawing of snow or ice.


Giardia: more properly known as giardiasis, an infection of the lower intestines cause by the amoebic cyst, Giardia lamblia. Giardia resides in water so it is wise to always chemically treat or filter your water before drinking. Symptoms include stomach cramps, diarrhea, bloating, loss of appetite and vomiting.

Grid : A grid is a pattern of squares on your map which serve to fix your position. Coordinates will provide numbers that allow you to find a horizontal line and also a vertical line and follow them to the point of intersection, placing you within that particular grid.


Hachure: short lines used to represent relief features that lie in the direction of the steepest slope.

Halogen Bulb: a clean burning bright bulb that maximizes light output with halogen gas that helps keep the interior of the bulb clean.

Housing: the rotating part of the compass that holds the damping fluid, the magnetic needle and has degrees engraved around its edge from 1 to 360. Also known as the Azimuth Ring.


Index line: the point at which the direction-of-travel arrow meets the housing and where the degree reading should be read to establish a bearing.



Knob: a prominent rounded hill or mountain.


Latitude: the distance in degrees north and south from the equator. These lines run laterally (horizontally) around the globe and parallel the equator. One minute of latitude equals one nautical mile.

Layover day: a rest day during an extended paddling, backpacking or adventuring trip.

LED: Light Emitting Diodes. Durable and long-lived lightbulbs. Up to 100,000 hours run time. Soft focus, short range. Less power than incandescent but can give 100's of hours of run time at low illumination levels.

Lumen: a measurement of the entire output of the bulb. Focus is not considered.

Longitude: the distance in degrees east and west from the prime meridian established in Greenwich, England. These lines run vertically (lengthwise) around the globe and connect each pole.


Magnetic lines: lines drawn onto a topographic map by the user to indicate the direction of magnetic north and to allow the map to speak the same directional language as the compass.

Magnetic north: the geographical region towards which all magnetic needles point. This point is approximately 1,300 miles south of true north and moves slightly each year due to the earth's rotation and the friction created between its solid crust and liquid center.

Map Datum: A datum refers to the reference point from which all maps are drawn. GPS is based universally on a grid for the entire earth that a GPS can interpret anywhere in the world called WGS-84. Unfortunately, many maps were published before GPS so they utilize different datums-reference points. In North America, the datum is called the North American Datum 1927 or NAD27. Be sure your GPS can interpret the map datums for the areas you will be in.

Map projection: the process of transforming a round object (the earth) into a flat object (a map) with the least amount of distortion. There is always some distortion caused in this process which is why grid lines are not perfectly parallel.

Meridian: an imaginary line circling the earth and passing through the geographic poles. All points on any meridian will have the same longitude.

Mineral soil: dirt that contains mostly minerals and very little organic matter.


NiCd: Nickel-Cadmium rechargeable battery. Rugged with high performance.

NiMH: Nickel-metal hydride rechargeable battery.


Organic soil: dirt that contains a high percentage of organic material. This kind of soil is poor for constructing trails through since it rots, breaks down, compacts and holds water.

Orienteering: using a map and compass in the field to determine your route of travel. Has commonly come to mean a type of competition at which competitors try to navigate across challenging terrain from point to point arriving at the finish first.

Orienting a map: turning the map so that it represents a one-dimensional image that comes as close to exactly paralleling the three-dimensional world you are standing in.

Orienting arrow: the north / south pointing arrow engraved or painted in red or black into the housing that is slightly wider than the magnetic needle and used to "box" or surround the magnetic needle when establishing a bearing.

Orienting lines: the lines on the bottom of the compass housing that parallel the orienting arrow.

Outslope: the downhill slope of well-constructed trail that allows water to drain.


Parallel of latitude: an imaginary line that circles the earth parallel to the equator. All points on a given parallel have the same latitude.

Pink snow: nature's laxative, this snow is filled with algae that is really green in color but has coated itself with a pink gel for protection from the sun. Eat some and spend the next day worshiping the porcelain throne.

Position fix: sometimes referred to as fixing your position and means establishing your exact position on a map in terms of a coordinate system such as latitude / longitude or UTM.

Prime meridian: this is the meridian that runs through Greenwich, England at a longitude of 0 degrees and is used as the position of origin for measurements of longitude.

Prismatic compass: a compass with a mirror designed to allow a user to see both distant objects being sighted and the compass face at the same time.

Protractor: sometimes built into a compass, this instrument allows you to determine and measure angles in degrees and is most useful when projecting magnetic lines across your map.

Puncheon: a log bridge built over fragile terrain that is wet.


Quadrangle: a four-sided section of land bounded by parallels of latitude and meridians of longitude depicted on or by a topographic map. Topo maps are sometimes referred to as "quads."


Ravine: a deep narrow cleft in the earth's surface usually caused by runoff.

Reflector (Flashlight): surrounds the bulb and focuses and directs the beam.

Relief: changes in terrain.

Relief shading: a process of shading the map so that it takes on a three-dimensional look. Typically, maps are shaded as if the light source casting the shadow is coming from the northwest.

Rock flour: a fine, silty sediment from glacially ground rock that causes creaks and mountain tarns to appear milky or greenish in color.

Runoff: rainfall that is not absorbed by the soil.


Saddle: a ridge between two peaks.

Scale: the distance between two points on a map as they relate to the distance between those two points on the earth.

Scree slope: a slope with an angle of at least 30 degrees and covered with small rocks and gravel that have broken away from the cliffs above.

Sighting line: sometimes called line of sight, this refers to the imaginary line that you sight along to take your bearing.

Skirt: to work your way around a mountain or obstacle.

Slick rock: common name for southwestern sandstone made slick by the rubbing and grinding action of sand.

Slot canyon: a narrow canyon carved into sandstone or slick rock by centuries of rain and flash flooding. Slot canyons are often filled or partially filled with water and can be extremely dangerous to navigate through.

Snow bridge: a layer or "bridge" of snow that can be inches or feet thick spanning a creek or crevasse. Bridges can and will collapse when walked on so extreme caution should be used.

Spur ridge: a side ridge that branches off the main ridge.

Stile: a structure built over a fence that allows hikers to cross over without having to deal with a gate. Common in Great Britain.

Switchback: zigzagging trail up the side of a steep ridge, hill or mountain. Allows for a more gradual and less strenuous ascent.


Talus slope: Talus slopes are more angled, sloping at 45 degrees or more, than a scree slope. Talus is also larger than scree and the rocks have sharper edges all of which makes a talus slope far more dangerous to cross and difficult to scramble up or down.

Tarn: a small mountain lake.

TFF (Time To First Fix): This is the amount of time it will take your GPS receiver to make its first position fix after it has been in the off position for over a month, lost its memory, or been moved for over 300 miles without an interim fix. Typically, this won't amount to more than 15 minutes.

Traverse: to go up, down, or across a slope at an angle.

Tread: a trail's surface.

True north: also known as geographic north-the North Pole.


Universal Transverse Mercator (UTM): UTM refers to the system grid that divides the entire world into 60 zones that are 6 degrees wide. The zones begin at east / west longitude 180 degrees and continue at 6 degree intervals. Each zone is then removed from the globe and flattened, losing its relationship to a sphere and introducing a certain amount of distortion. Since UTM projections distort the regions above 84 degrees north latitude and below 80 degrees south latitude far too much, they are not used on maps referencing the UTM grid. The UTM grid is based upon the meter and grid lines are always 1 kilometer (.62 miles) apart, making it much easier to estimate distance on a map. UTM coordinates are printed on a map in an east / west and north / south position. Numbers along the right side of a map are called northings (indicating the exact position in a north / south relationship). Numbers along the top of the map are called eastings (indicating the exact position in an east / west relationship).
Making sense of the numbers is quick and easy: Increasing easting numbers indicate you are heading east; decreasing indicate you are heading west. Increasing northing numbers indicate you are heading north; decreasing indicate you are heading south.



Waypoint: A checkpoint used as a point of reference for GPS.

Whiteout: A condition of zero or extremely limited visibility caused when fog or thick clouds or rapidly falling snow creates a situation where light from above is the same as the light being reflected off the snow so that there are no shadows and no visible horizon.


Xenon Bulb: a clean burning bright bulb that maximizes light output with Xenon gas that helps keep the interior of the bulb clean.

Yogiing: a despicable habit of dipping into others picnic baskets when they are not looking. Used to be just for food, but more recently has meant teens searching for booze.