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Use of The Compass

Sunday 1 January 2017, by Imeru Alfonzo Hernandez

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The compass is a magnetic needle that responds to the magnetic field of the earth (it was known and used by the Chinese 2,500 years before Christ), orienting itself accordingly. Measure the horizontal angle with respect to the magnetic field line in which it is located.

As previously mentioned in another article, the magnetic north tends to differ with the geographic north, so the calculation of the magnetic declination is used to find the true or geographical directions. In Venezuela the declines are all towards the west, so we must add the value of the declination to azimuth (geographical direction), and these vary according to the place. As this measure varies with time it is necessary to know the correct calculation of it.

Actual azimuth = compass measurement +/- magnetic declination.

It is the same to say that if you measure an address on the compass, you must add the local magnetic declination to the measure, and you will obtain real Azimuth. In order to have an idea of ​​how important this calculation can be, we present a table, Table 2, with estimates of objective errors due to the non-use of the Magnetic Declination.

Deviation by Magnetic Declination Error or deviation
of the Objective after
Walk 15 Kilometers
in plane
5 ° 1,307.34 meters
10 ° 2,604.72 meters
15 ° 3.882,29 meters


The most widespread use of the compass among hikers is to point directions, triangulate the position and create polygonal (routes formed by successions of straight paths of distances and known directions).


This technique is used to determine the approximate location in which we are located, and is done by locating two known or recognizable points that form an angle with our location, and then we take the values ​​obtained to the map


Know the position, we proceed by a similar process to locate our destination on the map, we measure its direction and then we take that result to reality, directly measuring the direction on the landscape

Obstacle Overcoming

In this way we surround the obstacles without losing the course of our trajectory, it is similar to following progressive orientations, fig. down.

Other forms of orientation

GPS. (Global positioning system) It works thanks to satellites in orbit that by means of a sensor and mathematical algorithms, they show the position and the height of the user, at least three satellites are needed to obtain location reading and four for a three-dimensional reading.

ALTIMETER. Shows the altitude of the instrument with respect to sea level. And it works thanks to the barometric pressure, which is a disadvantage, since the temperature and changes in atmospheric pressure distort the reading and introduce errors.

WITH THE CLOCK. Set the solar time and aim with the small hand towards the sun. The bisector of the angle formed by the small hand and twelve o’clock of the clock situates to the south.

SUN. An approximate indicator of the cardinal points is the sun. If at sunrise or in the morning we look straight at it, the right side of the observer will point south, and in the afternoon or evening it will point north, another good sign is that in the middle hours the shadows of the objects that are They are perpendicular to the floor and project to the south.

THE POLAR STAR. Besides being the only fixed star of the firmament it is located marking the geographic north. To locate it you have to draw an imaginary line that is five times the distant length between the last two stars of the Great Bear

(C) 1995 - 2018 Imeru Alfonzo Hernandez, Síguenos vía twitter e instagram por @imerualfonzo y @ecoExtremos