Compass what is

A magnetic compass's user can determine true North by finding the magnetic north and then correcting for variation and deviation. Variation is defined as the angle between the direction of true geographic north and the direction of the meridian between the magnetic poles. Variation values for most of the oceans had been calculated and published by Mariners have long known that these measures do not completely cancel deviation; hence, they performed an additional step by measuring the compass bearing of a landmark with a known magnetic bearing.

They then pointed their ship to the next compass point and measured again, graphing their results. In this way, correction tables could be created, which would be consulted when compasses were used when traveling in those locations. Mariners are concerned about very accurate measurements; however, casual users need not be concerned with differences between magnetic and true North. Except in areas of extreme magnetic declination variance 20 degrees or more , this is enough to protect from walking in a substantially different direction than expected over short distances, provided the terrain is fairly flat and visibility is not impaired.

By carefully recording distances time or paces and magnetic bearings traveled, one can plot a course and return to one's starting point using the compass alone. Compass navigation in conjunction with a map terrain association requires a different method. To take a map bearing or true bearing a bearing taken in reference to true, not magnetic north to a destination with a protractor compass , the edge of the compass is placed on the map so that it connects the current location with the desired destination some sources recommend physically drawing a line.

The orienting lines in the base of the compass dial are then rotated to align with actual or true north by aligning them with a marked line of longitude or the vertical margin of the map , ignoring the compass needle entirely. If a magnetic north bearing or compass bearing is desired, the compass must be adjusted by the amount of magnetic declination before using the bearing so that both map and compass are in agreement.

Some compasses allow the scale to be adjusted to compensate for the local magnetic declination; if adjusted correctly, the compass will give the true bearing instead of the magnetic bearing. The modern hand-held protractor compass always has an additional direction-of-travel DOT arrow or indicator inscribed on the baseplate. To check one's progress along a course or azimuth, or to ensure that the object in view is indeed the destination, a new compass reading may be taken to the target if visible here, the large mountain.

After pointing the DOT arrow on the baseplate at the target, the compass is oriented so that the needle is superimposed over the orienting arrow in the capsule. The resulting bearing indicated is the magnetic bearing to the target. Again, if one is using "true" or map bearings, and the compass does not have preset, pre-adjusted declination, one must additionally add or subtract magnetic declination to convert the magnetic bearing into a true bearing. The exact value of the magnetic declination is place-dependent and varies over time, though declination is frequently given on the map itself or obtainable on-line from various sites.

If the hiker has been following the correct path, the compass' corrected true indicated bearing should closely correspond to the true bearing previously obtained from the map. Licensed under the Creative Commons Attribution Non-commercial 3. Circuit diagram. Mark The Ultimate Desert Handbook. McGraw-Hill Professional. See synonyms for compass on Thesaurus. Also called range. Often compasses. Also called Mariner's Compass. Compasses, the constellation Circinus. We could talk until we're blue in the face about this quiz on words for the color "blue," but we think you should take the quiz and find out if you're a whiz at these colorful terms.

Origin of compass —; v. See range. Words nearby compass compartment , compartmental , compartmentalization , compartmentalize , compartmentation , compass , compass card , compass course , compass deviation , compass deviation card , compassion. Words related to compass ambit , area , bound , circle , circuit , circumference , circumscription , confines , domain , enclosure , environs , expanse , extent , field , limit , limitation , orbit , perimeter , precinct , purlieus.

How to use compass in a sentence I fundamentally feel that the Gallaudet Board of Trustees has lost its way and its moral compass. Clara thought she had never seen him look so small and mean. He was as if trying to get himself into the smallest possible compass. Gabriel thought back to the three items he'd discovered in her jewelry box: the compass , a soul and the tarnished ring he gave her hundreds of years ago.

The compass needle is a little steel magnet balanced upon a pivot; one end of the needle, which always bears a distinguishing mark, points approximately, but not in general exactly, to the north,' the vertical plane through the direction of the needle being termed the magnetic meridian. I think the compass tells you what kind of soul it is. All rights reserved. Filters 0.

Words form: compasses. See word origin. A compass is defined as a device with magnetic needles used for showing the direction one is facing. Awareness or understanding of one's purpose or objectives. The definition of compass means to understand, grasp or fulfill. The definition of a compass is a tool with two pointed legs connected by a hinge, one end with a writing device the other used as a stable pivot, used for drawing perfect circles and other things. A device used for drawing circles and arcs and for measuring distances on maps, consisting of two legs hinged together at one end.

A pair of compasses a device used to draw an arc or circle. Moderate bounds, limits of truth; moderation; due limits; used with within.