Portable compasses are essential tools for surveying and navigation. They are commonly used in outdoor activities such as hiking, orienteering, and camping, as well as in professional fields such as surveying, cartography, and engineering. There are different types of compasses, each with specific characteristics that suit specific needs.
Types of Portable Compasses
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Ball compasses : These are among the simplest and most commonly used compasses. They are used to determine direction instantly.
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Marching (or orienteering) compasses : These compasses are designed for use in land navigation situations. Many have a magnifying glass for map reading, a distance scale, and a gyroscope or compensator for precise orientation.
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Clinometer compasses : These are used to determine the inclination of a surface or the slope of a terrain, very useful in geological or land surveying contexts.
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Digital compasses : These integrate modern technology and are often able to also provide data such as latitude, longitude and altitude, with digital readouts.
Surveying with Compasses
Compass surveying is a precision activity, and is usually accompanied by a topographical map. A map's orientation to the terrain is determined using the north point (magnetic north), which is found with the compass. Here are some basic steps:
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Determining direction : The compass allows you to determine your direction, which can be expressed in degrees from magnetic north. It's important to know the magnetic deviation, which can vary depending on your geographic location.
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Map Orientation : The map is oriented by aligning the compass direction with that indicated by the map, taking into account local magnetic deviations.
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Using Magnetic Declination : Magnetic declination is the angular difference between geographic (true) north and magnetic north. Maps typically indicate this difference to allow for correction.
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Route Planning : Using the compass in conjunction with the map, you can plot your route, taking into account distance and elevation changes.
Applications in Sensing
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Surveying and Geodesy : The compass is used in conjunction with other instruments to measure angles, slopes, and distances, essential for creating maps and determining the precise location of geodetic points.
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Navigation and Orientation : Navigators use the compass to keep track of their course when no GPS signal is available. It is also used in survival situations.
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Construction and Engineering : Compasses are used to measure angles of buildings or structures, ensuring they are correctly aligned during construction.
The key to good bearing is practice using a compass, developing an understanding of the necessary compensations (such as magnetic declination) and how to read maps accurately.
