The purpose of the tritium and phosphors is to provide illumination for the compass, via radioluminescent tritium illumination, which does not require the compass to be "recharged" by sunlight or artificial light.
However, tritium has a half-life of only about 12 years, so a compass that contains mCi of tritium when new will contain only 60 when it is 12 years old, 30 when it is 24 years old, and so on. Consequently, the illumination of the display will fade.
Mariner's compasses can have two or more magnets permanently attached to a compass card, which moves freely on a pivot. A lubber line , which can be a marking on the compass bowl or a small fixed needle, indicates the ship's heading on the compass card. Traditionally the card is divided into thirty-two points known as rhumbs , although modern compasses are marked in degrees rather than cardinal points.
The glass-covered box or bowl contains a suspended gimbal within a binnacle. This preserves the horizontal position. A thumb compass is a type of compass commonly used in orienteering , a sport in which map reading and terrain association are paramount.
Consequently, most thumb compasses have minimal or no degree markings at all, and are normally used only to orient the map to magnetic north. Thumb compasses are also often transparent so that an orienteer can hold a map in the hand with the compass and see the map through the compass.
A gyrocompass is similar to a gyroscope. It is a non-magnetic compass that finds true north by using an electrically powered fast-spinning wheel and friction forces in order to exploit the rotation of the Earth. Gyro compasses are widely used on ships. They have two main advantages over magnetic compasses:. Large ships typically rely on a gyrocompass, using the magnetic compass only as a backup. Increasingly, electronic fluxgate compasses are used on smaller vessels.
However, magnetic compasses are still widely in use as they can be small, use simple reliable technology, are comparatively cheap, are often easier to use than GPS , require no energy supply, and unlike GPS, are not affected by objects, e. Small compasses found in clocks, mobile phones , and other electronic devices are solid-state compasses, usually built out of two or three magnetic field sensors that provide data for a microprocessor.
Often, the device is a discrete component which outputs either a digital or analog signal proportional to its orientation. This signal is interpreted by a controller or microprocessor and either used internally, or sent to a display unit. The sensor uses highly calibrated internal electronics to measure the response of the device to the Earth's magnetic field. GPS receivers using two or more antennae mounted separately and blending the data with an inertial motion unit IMU can now achieve 0.
The devices accurately determine the positions latitudes, longitudes and altitude of the antennae on the Earth, from which the cardinal directions can be calculated. Manufactured primarily for maritime and aviation applications, they can also detect pitch and roll of ships. Small, portable GPS receivers with only a single antenna can also determine directions if they are being moved, even if only at walking pace.
By accurately determining its position on the Earth at times a few seconds apart, the device can calculate its speed and the true bearing relative to true north of its direction of motion. Frequently, it is preferable to measure the direction in which a vehicle is actually moving, rather than its heading, i. These directions may be different if there is a crosswind or tidal current. GPS compasses share the main advantages of gyrocompasses. They determine true North, as opposed to magnetic North, and they are unaffected by perturbations of the Earth's magnetic field.
Additionally, compared with gyrocompasses, they are much cheaper, they work better in polar regions, they are less prone to be affected by mechanical vibration, and they can be initialized far more quickly. However, they depend on the functioning of, and communication with, the GPS satellites, which might be disrupted by an electronic attack or by the effects of a severe solar storm.
Gyrocompasses remain in use for military purposes especially in submarines, where magnetic and GPS compasses are useless , but have been largely superseded by GPS compasses, with magnetic backups, in civilian contexts.
Apart from navigational compasses, other specialty compasses have also been designed to accommodate specific uses. These include:. The magnetic compass is very reliable at moderate latitudes, but in geographic regions near the Earth's magnetic poles it becomes unusable.
As the compass is moved closer to one of the magnetic poles, the magnetic declination, the difference between the direction to geographical north and magnetic north, becomes greater and greater. At some point close to the magnetic pole the compass will not indicate any particular direction but will begin to drift.
Also, the needle starts to point up or down when getting closer to the poles, because of the so-called magnetic inclination. Cheap compasses with bad bearings may get stuck because of this and therefore indicate a wrong direction.
Magnetic compasses are influenced by any fields other than Earth's. Local environments may contain magnetic mineral deposits and artificial sources such as MRIs , large iron or steel bodies, electrical engines or strong permanent magnets. Any electrically conductive body produces its own magnetic field when it is carrying an electric current.
Magnetic compasses are prone to errors in the neighborhood of such bodies. Some compasses include magnets which can be adjusted to compensate for external magnetic fields, making the compass more reliable and accurate. A compass is also subject to errors when the compass is accelerated or decelerated in an airplane or automobile. Depending on which of the Earth's hemispheres the compass is located and if the force is acceleration or deceleration the compass will increase or decrease the indicated heading.
Compasses that include compensating magnets are especially prone to these errors, since accelerations tilt the needle, bringing it closer or further from the magnets. Another error of the mechanical compass is turning error.
When one turns from a heading of east or west the compass will lag behind the turn or lead ahead of the turn. Magnetometers, and substitutes such as gyrocompasses, are more stable in such situations. A magnetic rod is required when constructing a compass. This can be created by aligning an iron or steel rod with Earth's magnetic field and then tempering or striking it. However, this method produces only a weak magnet so other methods are preferred. For example, a magnetised rod can be created by repeatedly rubbing an iron rod with a magnetic lodestone.
This magnetised rod or magnetic needle is then placed on a low friction surface to allow it to freely pivot to align itself with the magnetic field. It is then labeled so the user can distinguish the north-pointing from the south-pointing end; in modern convention the north end is typically marked in some way.
If a needle is rubbed on a lodestone or other magnet, the needle becomes magnetized. When it is inserted in a cork or piece of wood, and placed in a bowl of water it becomes a compass. Such devices were universally used as compass until the invention of the box-like compass with a 'dry' pivoting needle sometime around Originally, many compasses were marked only as to the direction of magnetic north, or to the four cardinal points north, south, east, west.
Later, these were divided, in China into 24, and in Europe into 32 equally spaced points around the compass card. For a table of the thirty-two points, see compass points. In the modern era, the degree system took hold.
This system is still in use today for civilian navigators. The degree system spaces equidistant points located clockwise around the compass dial. In the 19th century some European nations adopted the "grad" also called grade or gon system instead, where a right angle is grads to give a circle of grads. Dividing grads into tenths to give a circle of decigrades has also been used in armies. Most military forces have adopted the French "millieme" system.
This is an approximation of a milli-radian per circle , in which the compass dial is spaced into units or "mils" for additional precision when measuring angles, laying artillery, etc. The value to the military is that one angular mil subtends approximately one metre at a distance of one kilometer. Imperial Russia used a system derived by dividing the circumference of a circle into chords of the same length as the radius. Each of these was divided into spaces, giving a circle of The Soviet Union divided these into tenths to give a circle of units, usually translated as "mils".
This system was adopted by the former Warsaw Pact countries e. Soviet Union , East Germany , often counterclockwise see picture of wrist compass. This is still in use in Russia. Because the Earth's magnetic field's inclination and intensity vary at different latitudes, compasses are often balanced during manufacture so that the dial or needle will be level, eliminating needle drag which can give inaccurate readings.
Most manufacturers balance their compass needles for one of five zones, ranging from zone 1, covering most of the Northern Hemisphere , to zone 5 covering Australia and the southern oceans. This individual zone balancing prevents excessive dipping of one end of the needle which can cause the compass card to stick and give false readings. Some compasses feature a special needle balancing system that will accurately indicate magnetic north regardless of the particular magnetic zone.
Other magnetic compasses have a small sliding counterweight installed on the needle itself. This sliding counterweight, called a 'rider', can be used for counterbalancing the needle against the dip caused by inclination if the compass is taken to a zone with a higher or lower dip.
Like any magnetic device, compasses are affected by nearby ferrous materials, as well as by strong local electromagnetic forces. Compasses used for wilderness land navigation should not be used in proximity to ferrous metal objects or electromagnetic fields car electrical systems, automobile engines, steel pitons, etc.
Compasses are particularly difficult to use accurately in or near trucks, cars or other mechanized vehicles even when corrected for deviation by the use of built-in magnets or other devices. Large amounts of ferrous metal combined with the on-and-off electrical fields caused by the vehicle's ignition and charging systems generally result in significant compass errors.
At sea, a ship's compass must also be corrected for errors, called deviation, caused by iron and steel in its structure and equipment. Nov 15, This is pretty cool my cousin liked this article too! Nov 11, We're glad you two liked this Wonder! Would you use a real compass out in the woods? Nov 4, We agree, mason!
Absolutely magnetic! Devin Oct 2, Oct 3, Hi Devin! Have you used a compass before? I have used a compass before when I was hiking. Riley smith Sep 17, Sep 18, That's great, Riley! Thanks for sharing! Sep 16, Were you able to navigate during your hike? Dec 10, Thanks, some dude! Have you ever used a compass? Max May 18, May 22, Keegbob Jan 19, Hiya dude!!!!!! Jan 20, Keegbob Jan 20, Jan 23, Keegbob Jan 24, Jan 25, Awesome, Rowan!
We are so glad that you liked it and that you let us know! William Jan 18, Thank you because I am excited to chat and sing. I have seen the "Do You Karaoke? Thx for commenting! William Feb 9, I hadn't commented in a long time so Hi and I hope you guys love this!
Feb 10, Welcome back, William! Great to hear from you again! Jan 19, No problem, William! Yes, I saw animals like deer and birds and other things.
Very cool, William! We bet that was a great trip. Thanks for responding to us! William Jan 17, I love commenting so comment to me everyday! I went camping and had a compass. Instead of using it, I used the Sun as the compass. Nature helps you a lot. Jan 18, William Jan 12, Compasses are cool. I have used one before thx! Jan 12, RunFastMcChuncky Feb 18, This is coooooooooooooooooooooooooooooooooolllllllllllllllllllllllll.
Feb 19, We're glad you had fun exploring this Wonder! Patrick Feb 8, Wonderopolis Feb 9, We are glad you enjoyed the video! Patrick Jan 30, Wonderopolis Feb 2, Jonathan Hay Jan 12, Wonderopolis Jan 12, We do too, Jonathan Hay! They can be very useful when you don't know your way! Cameron V. Jan 9, The article had a lot of information about compasses. I enjoyed reading it. Teagan Jan 9, Dear wonderoplis, I always wondered how a compas worked.
I have not used a compas for a life or death situation ,but i have used one. This is very interesting. Welcome, jackson! Wonderopolis Jan 9, Hanna Jan 9, How does the compass work west south or east That is a really hard question. Blair Whitfield Jan 9, GPS's are like the new version of compasses. A compass is just a round object that contains a small lightweight magnet usually called a needle by it's shape balanced on a pivot point that allows it to move freely.
On the oppisite side of the compass it points to south, and when you see the sun come up you know that is east and the oppisite of east is west. And if you need a compass to navigate thousands of miles, it's important to know there's a difference between Earth's magnetic North Pole where a compass points and a "true north" which is Earth's geographic location known as the North Pole.
Thomas Jan 9, Their question was not good because there are two types of compasses. Elexeanna Jan 9, A compass is what you need when you get lost it tells you directions like a map.
Marcus Jan 9, A compass is something that tells you where you going. If you get lost and you have a compass with you it'll be easy to tell where you're going. Sometimes they call it a needle. Hi Marcus! Don't forget that the needle always points to the north. Ryan Scott Bedley Jan 9, I lernd that a compos can take you to the north poul from anywere in the world. Quinn Jan 9, If the true north moves then will eventually point south? That's a great question, Quinn! Trenten Jan 9, I learned that the scientist at Oregon University believes that the magnetic North Pole has moved miles toward Sideria over the last century.
That's an interesting fact, Trenton! Jacob Jan 9, A compass helps people find their way when they are lost. Tagan Jan 9, People have been using compass for a very long time. Gregory Jan 9, Why do we need compasses to tell us which way to go. It is cool to know that magnetic North Pole moved over miles. That is interesting, alysa!
Leah Jan 9, I learned that the needle in a compass is a magnet and it attracts to the earths North Pole magnetic field. Great information, Leah! Thanks for sharing what you learned with us! Jaquarius Jan 9, I learned that a GPS is a relative new invention that the explorers made. Since learned that the needle in a compass is a magnet so it attracts to the earths magnetic field.
Why do we need compasses to know which way to go. Deron Jan 9, What will happen if there was no magnetic field. Jahirah Jan 9, Charity Jan 9, Trazariya Jan 9, I learned how the compass move to the north and the south. How come the east and west is not on the compass rose? Related Wonders for You to Explore Match its definition: a movement, bend, or slope downward. Word Match Congratulations! Share results. Play Again Quit. Next Question. See your results. Share Results.
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