89-715: USS O-6 (SS-67) was an O-class submarine in commission in the United States Navy from 1918 to 1931 and from 1941 to 1945. She served in both World War I and World War II . O-6 ′s keel was laid down on 6 December 1916 by the Fore River Shipbuilding Company in Quincy , Massachusetts . She was launched on 25 November 1917, sponsored by Mrs. Carroll Q. Wright, the daughter of United States Army Major John Leslie Shepard and wife of O-6 ′s prospective commanding officer . O-6
178-465: A binnacle . This preserves the horizontal position. 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
267-480: A jewel bearing , so it can turn easily. When the compass is held level, the needle turns until, after a few seconds to allow oscillations to die out, it settles into its equilibrium orientation. In navigation, directions on maps are usually expressed with reference to geographical or true north , the direction toward the Geographical North Pole , the rotation axis of the Earth. Depending on where
356-526: A bowl of water it becomes a compass. Such devices were universally used as compasses until the invention of the box-like compass with a "dry" pivoting needle, sometime around 1300. 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
445-405: 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
534-413: A compass, for example, certain rocks which contain magnetic minerals, like Magnetite . This is often indicated by a rock with a surface which is dark and has a metallic luster, not all magnetic mineral bearing rocks have this indication. To see if a rock or an area is causing interference on a compass, get out of the area, and see if the needle on the compass moves. If it does, it means that the area or rock
623-653: A device for divination as early as the Chinese Han dynasty (since c. 206 BC), and later adopted for navigation by the Song dynasty Chinese during the 11th century. The first usage of a compass recorded in Western Europe and the Islamic world occurred around 1190. The magnetic compass is the most familiar compass type. It functions as a pointer to " magnetic north ", the local magnetic meridian, because
712-457: 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
801-496: A few nations, notably the United States Army, continue to issue field compasses with magnetized compass dials or cards instead of needles. A magnetic card compass is usually equipped with an optical, lensatic, or prismatic sight , which allows the user to read the bearing or azimuth off the compass card while simultaneously aligning the compass with the objective (see photo). Magnetic card compass designs normally require
890-650: A fire in her conning tower in December 1919. All six of the Lake design boats were decommissioned in July 1924, with five being scrapped in July 1930 under the terms of the London Naval Treaty . However, the decommissioned O-12 was leased back to Simon Lake for use in an Arctic expedition by Sir Hubert Wilkins . Disarmed, she was rebuilt with specialized Arctic exploration equipment and renamed Nautilus . After
979-437: A fixed point while its heading is noted by alignment with fixed points on the shore. A compass deviation card is prepared so that the navigator can convert between compass and magnetic headings. The compass can be corrected in three ways. First the lubber line can be adjusted so that it is aligned with the direction in which the ship travels, then the effects of permanent magnets can be corrected for by small magnets fitted within
SECTION 10
#17327796386091068-399: A flexible rubber diaphragm or airspace inside the capsule to allow for volume changes caused by temperature or altitude, some modern liquid compasses use smaller housings and/or flexible capsule materials to accomplish the same result. The liquid inside the capsule serves to damp the movement of the needle, reducing oscillation time and increasing stability. Key points on the compass, including
1157-580: A lodestone, which appeared in China by 1088 during the Song dynasty , as described by Shen Kuo . Dry compasses began to appear around 1300 in Medieval Europe and the Islamic world . This was supplanted in the early 20th century by the liquid-filled magnetic compass. Modern compasses usually use a magnetized needle or dial inside a capsule completely filled with a liquid (lamp oil, mineral oil, white spirits, purified kerosene, or ethyl alcohol are common). While older designs commonly incorporated
1246-405: 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
1335-455: A map with the latest declination information should be used. Some magnetic compasses include means to manually compensate for the magnetic declination, so that the compass shows true directions. The first compasses in ancient Han dynasty China were made of lodestone , a naturally magnetized ore of iron. The wet compass reached Southern India in the 4th century AD. Later compasses were made of iron needles, magnetized by striking them with
1424-627: A map. Other features found on modern orienteering compasses are map and romer scales for measuring distances and plotting positions on maps, luminous markings on the face or bezels, various sighting mechanisms (mirror, prism, etc.) for taking bearings of distant objects with greater precision, gimbal-mounted, "global" needles for use in differing hemispheres, special rare-earth magnets to stabilize compass needles, adjustable declination for obtaining instant true bearings without resorting to arithmetic, and devices such as inclinometers for measuring gradients. The sport of orienteering has also resulted in
1513-434: A marked line of longitude (or the vertical margin of the map), ignoring the compass needle entirely. The resulting true bearing or map bearing may then be read at the degree indicator or direction-of-travel (DOT) line, which may be followed as an azimuth (course) to the destination. If a magnetic north bearing or compass bearing is desired, the compass must be adjusted by the amount of magnetic declination before using
1602-533: 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. Apart from navigational compasses, other specialty compasses have also been designed to accommodate specific uses. These include: A magnetic rod
1691-419: A needle lock is fitted to the compass to reduce wear, operated by the folding action of the rear sight/lens holder. The use of air-filled induction compasses has declined over the years, as they may become inoperative or inaccurate in freezing temperatures or extremely humid environments due to condensation or water ingress. Some military compasses, like the U.S. M-1950 ( Cammenga 3H) military lensatic compass,
1780-571: A range of 3,000 yards (2,740 m). Jason fired eight rounds, scoring five hits. After the first hit, O-6 attempted to dive, but the second hit struck her conning tower and started leaks that made it impossible for her to submerge. O-6 blew her ballast tanks and returned to the surface. She flashed recognition signals by blinker light and members of her crew waved a United States flag on her deck. Jason reported that O-6 fired six shots from her deck gun at Jason , apparently misinterpreting O-6 ′s recognition signals as gun flashes. Another of
1869-655: A second-line submarine on 25 July 1924 while stationed at Coco Solo in the Panama Canal Zone , she reverted to first-line status on 6 June 1928 and continued to operate from New London until February 1929, when she proceeded to Philadelphia. She was decommissioned there on 9 June 1931. As U.S. involvement in World War II approached, the U.s. NAvy began to recommission old submarines for use as training ships. O-6 recommissioned at Philadelphia on 4 February 1941, then returned to New London to train students at
SECTION 20
#17327796386091958-403: A separate magnetized needle inside a rotating capsule, an orienting "box" or gate for aligning the needle with magnetic north, a transparent base containing map orienting lines, and a bezel (outer dial) marked in degrees or other units of angular measurement. The capsule is mounted in a transparent baseplate containing a direction-of-travel (DOT) indicator for use in taking bearings directly from
2047-469: A separate protractor tool in order to take bearings directly from a map. The U.S. M-1950 military lensatic compass does not use a liquid-filled capsule as a damping mechanism, but rather electromagnetic induction to control oscillation of its magnetized card. A "deep-well" design is used to allow the compass to be used globally with a card tilt of up to 8 degrees without impairing accuracy. As induction forces provide less damping than fluid-filled designs,
2136-753: A small sliding counterweight installed on the needle. 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.) as that can affect their accuracy. Compasses are particularly difficult to use accurately in or near trucks, cars or other mechanized vehicles even when corrected for deviation by
2225-519: A submarine in sight. Paul Jones then closed with O-6 and opened 3-inch (76.2 mm) gunfire, but all of her shots fell short, and she ceased fire when she closed to a range of 3,000 yards (2,700 m) and saw that O-6 was flying a U.S. flag from her conning tower. Paul Jones came alongside O-6 to render assistance. O-6 suffered no casualties, but she had sustained serious damage, including to her compasses — which had been knocked out — and her steering gear. Paul Jones escorted her to port at
2314-467: Is 100 grads to give a circle of 400 grads. Dividing grads into tenths to give a circle of 4000 decigrades has also been used in armies. Most military forces have adopted the French " millieme " system. This is an approximation of a milli-radian (6283 per circle), in which the compass dial is spaced into 6400 units or "mils" for additional precision when measuring angles, laying artillery, etc. The value to
2403-412: 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
2492-408: 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 1914. Deviation refers to the response of the compass to local magnetic fields caused by the presence of iron and electric currents; one can partly compensate for these by careful location of
2581-420: 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
2670-404: 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
2759-732: 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. Gyrocompasses 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.g. trees, that can block
USS O-6 - Misplaced Pages Continue
2848-454: 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
2937-591: The Lake Torpedo Boat Company and differed considerably from the EB design. All had the same military characteristics and performance and thus were considered by the Navy to be the same class. The EB design boats had a spindle shaped hull with an axially mounted rudder and twin lateral mounted propeller shafts. The bow diving planes controlled depth with the stern diving planes (mounted laterally behind
3026-556: The Naval Submarine Base New London , Connecticut . The looming war emergency forced the work to be rushed, and many of the eight O-class still needed thorough maintenance after being recommissioned. O-9 sank during deep submergence trials in June 1941, likely due to her poor material condition. Thirty-three of her crew were lost. In 1929–1930 the EB design O-class boats were modified for improved safety in
3115-482: 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
3204-516: The Silva 4b Militaire , and the Suunto M-5N(T) contain the radioactive material tritium ( 1 H ) and a combination of phosphors. The U.S. M-1950 equipped with self-luminous lighting contains 120 mCi (millicuries) of tritium. The purpose of the tritium and phosphors is to provide illumination for the compass, via radioluminescent tritium illumination , which does not require
3293-530: The armistice with Germany of 11 November 1918 brought World War I to an end before the submarines reached the Azores . They returned to the United States. After World War I, O-6 operated as a training ship from Naval Submarine Base New London at Groton , Connecticut . When the U.S. Navy adopted its hull classification system on 17 July 1920, she received the hull number SS-67 . Reclassified as
3382-510: The magnetized needle at its heart aligns itself with the horizontal component of the Earth's magnetic field . The magnetic field exerts a torque on the needle, pulling the North end or pole of the needle approximately toward the Earth's North magnetic pole , and pulling the other toward the Earth's South magnetic pole . The needle is mounted on a low-friction pivot point, in better compasses
3471-509: The Delaware Breakwater, where they arrived on 8 August 1918. O-6 received a commendation for her crew's conduct during the incident. Lieutenant Wright was promoted to lieutenant commander on 15 August 1918 and later was awarded a Navy Distinguished Service Medal , the citation for which says, "The courage and coolness with which Lieutenant Commander Wright handled his vessel under these very trying conditions undoubtedly saved
3560-588: The EB design were built by Fore River Shipyard , Quincy, Massachusetts . O-11 through O-13 were Lake design built by the Lake Torpedo Boat Company of Bridgeport, Connecticut . Once again desirous of having submarines built at a west coast yard, the Navy got Lake to build the O-14 through O-16 at a sub-contractor named California Shipbuilding (formerly Craig Shipbuilding ), Long Beach, California . CALSHIP suffered from numerous management and production issues and all three boats assigned to them had to be towed up
3649-671: The Navy to retain the old Mk 7 torpedo, solely for the use by these boats. All other 18-inch torpedoes prior to the 21-inch Mk 8 were discarded before WWII as a cost saving measure. During World War II, the seven remaining O boats were stationed at the New London Submarine Base and served as training platforms for the Submarine School. The last O-boat, USS O-4 , was decommissioned in September 1945. O-4 had served for 27 years and was, at that time,
USS O-6 - Misplaced Pages Continue
3738-594: The Submarine School. On 19 June 1941, she made a trial run to Portsmouth , New Hampshire , and the next day the submarine USS O-9 (SS-70) sank 15 nautical miles (28 km; 17 mi) off Portsmouth. O-6 joined the submarines USS O-10 (SS-71) and USS Triton (SS-201) and other vessels in the search for O-9 , but to no avail. O-6 remained in the Portsmouth area. The United States entered World War II on 7 December 1941, and she carried out training duties from Portsmouth through
3827-688: The USN from 1918 through the end of World War II . Following the design trend of the day, these boats were scaled up versions of the preceding L class , reversing the fiscally created shrinkage in size of the N class . The O class were about 80 tons larger than the L class, with greater power and endurance for wider ranging patrols. Due to the American entry into World War I the O class were built much more rapidly than previous classes, and were all commissioned in 1918. O-1 through O-10 were designed by Electric Boat (EB), O-11 through O-16 were designed by
3916-508: The angled-diving technique used by the EB design boats. Zero-angle diving proved to be unworkable and Lake used it here for the last time. His design for the follow-on R-class boats would abandon the method in favor of the EB angle-diving arrangement. Unusually, the Navy obtained a legal license to build two of the EB design boats at government owned Navy Yards: O-1 by Portsmouth Navy Yard , Kittery, Maine , and O-2 by Puget Sound Navy Yard , Bremerton, Washington . O-3 through O-10 of
4005-476: The angles increase clockwise , so east is 90°, south is 180°, and west is 270°. These numbers allow the compass to show azimuths or bearings which are commonly stated in degrees. If local variation between magnetic north and true north is known, then direction of magnetic north also gives direction of true north. Among the Four Great Inventions , the magnetic compass was first invented as
4094-459: 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
4183-489: The bearing so that both map and compass are in agreement. In the given example, the large mountain in the second photo was selected as the target destination on the map. 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
4272-414: 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
4361-442: The case of the compass. The effect of ferromagnetic materials in the compass's environment can be corrected by two iron balls mounted on either side of the compass binnacle in concert with permanent magnets and a Flinders bar . The coefficient a 0 {\displaystyle a_{0}} represents the error in the lubber line, while a 1 , b 1 {\displaystyle a_{1},b_{1}}
4450-620: The coast to the Mare Island Navy Yard north of San Francisco in Vallejo, California for completion. The class originally operated in the anti-submarine role off the United States' East Coast. Two of the boats, O-4 and O-6 , mistakenly came under fire from a British merchant ship in the Atlantic on 24 July 1918. The steamer scored six hits on O-4 ' s conning tower fairwater and pressure hull before her identity
4539-749: The compass and the placement of compensating magnets under the compass itself. 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
SECTION 50
#17327796386094628-407: The compass card. For a table of the thirty-two points, see compass points . In the modern era, the 360-degree system took hold. This system is still in use today for civilian navigators. The degree system spaces 360 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
4717-409: 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 the turning error. When one turns from a heading of east or west
4806-451: The compass is located on the surface of the Earth the angle between true north and magnetic north , called magnetic declination can vary widely with geographic location. The local magnetic declination is given on most maps, to allow the map to be oriented with a compass parallel to true north. The locations of the Earth's magnetic poles slowly change with time, which is referred to as geomagnetic secular variation . The effect of this means
4895-400: 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 120 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. Mariners' compasses can have two or more magnets permanently attached to
4984-400: The compass was previously at is causing interference and should be avoided. There are other ways to find north than the use of magnetism, and from a navigational point of view a total of seven possible ways exist (where magnetism is one of the seven). Two sensors that use two of the remaining six principles are often also called compasses, i.e. the gyrocompass and GPS-compass. A gyrocompass
5073-410: 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 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
5162-522: The conclusion of the expedition she was scuttled in a Norwegian fjord in November 1931 to keep within the provisions of the lease agreement, as the Navy no longer wanted her but didn't want the boat to fall into foreign hands. The EB design boats served well although O-5 was rammed by a cargo ship and sunk near the Panama Canal on 28 October 1923 with the loss of three crew members. All nine of
5251-422: The convoy's cargo ships also opened fire, and shell splashes from that ship's gunfire fell short of O-6 and may have appeared to Jason ′s crew and gunners to have come from O-6 . O-6 stopped, and Jason ceased fire as she steamed out of range of O-6 . One of the convoy's escorts, the U.S. Navy destroyer USS Paul Jones , had meanwhile reversed course and approached Jason , which signaled that she had
5340-409: The correct local compass variation so as to indicate the true heading. ‹The template How-to is being considered for merging .› A magnetic compass points to magnetic north pole, which is approximately 1,000 miles from the true geographic North Pole. A magnetic compass's user can determine true North by finding the magnetic north and then correcting for variation and deviation. Variation
5429-425: The development of models with extremely fast-settling and stable needles utilizing rare-earth magnets for optimal use with a topographic map , a land navigation technique known as terrain association . Many marine compasses designed for use on boats with constantly shifting angles use dampening fluids such as isopar M or isopar L to limit the rapid fluctuation and direction of the needle. The military forces of
SECTION 60
#17327796386095518-565: The end of the war, which concluded with the surrender of Japan on 15 August 1945. O-6 was decommissioned at Portsmouth on 11 September 1945. She was struck from the Naval Vessel Register the same day, and was sold to John J. Duane Company of Quincy, Massachusetts, on 4 September 1946. She was scrapped in December 1946. United States O-class submarine The United States Navy (USN)'s sixteen O-class coastal patrol submarines were built during World War I and served
5607-506: The event of sinking. This was work prompted by the loss of the S-4 in 1927. Two marker buoys were added fore and aft. In the event the submarine was stranded on the bottom the buoys could be released to show the submarine's position. A motor room escape hatch was also added, the motor room being the after most compartment. The tapered after dorsal skeg became a step as a result of these modifications. The 18-inch torpedo tubes of this class forced
5696-463: The ferromagnetic effects and a 2 , b 2 {\displaystyle a_{2},b_{2}} the non-ferromagnetic component. A similar process is used to calibrate the compass in light general aviation aircraft, with the compass deviation card often mounted permanently just above or below the magnetic compass on the instrument panel. Fluxgate electronic compasses can be calibrated automatically, and can also be programmed with
5785-420: 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. A compass should be laid down on a level surface so that the needle only rests or hangs on the bearing fused to the compass casing – if used at a tilt, the needle might touch the casing on the compass and not move freely, hence not pointing to
5874-416: The last of the EB designs with the cap. The Lake design used individual muzzle doors with hydro-dynamic shutters to seal the tubes, a feature that would become standard on all later USN submarines. These boats were big enough to have a semi-retractable 3-inch/23-caliber gun on the deck forward of the conning tower fairwater . This gun partially retracted into a vertical watertight cylinder that penetrated
5963-676: The longest serving submarine in the history of the US Navy. The 16 submarines of the O class were: Electric Boat (EB) design Lake Torpedo Boat Company design Compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose , which can pivot to align itself with magnetic north . Other methods may be used, including gyroscopes, magnetometers , and GPS receivers. Compasses often show angles in degrees: north corresponds to 0°, and
6052-536: The magnetic north accurately, giving a faulty reading. To see if the needle is well leveled, look closely at the needle, and tilt it slightly to see if the needle is swaying side to side freely and the needle is not contacting the casing of the compass. If the needle tilts to one direction, tilt the compass slightly and gently to the opposing direction until the compass needle is horizontal, lengthwise. Items to avoid around compasses are magnets of any kind and any electronics. Magnetic fields from electronics can easily disrupt
6141-647: 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
6230-418: The map to magnetic north. An oversized rectangular needle or north indicator aids visibility. 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. The best models use rare-earth magnets to reduce needle settling time to 1 second or less. The earth inductor compass (or "induction compass") determines directions using
6319-415: 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 100 spaces, giving a circle of 600. The Soviet Union divided these into tenths to give a circle of 6000 units, usually translated as "mils". This system
6408-465: The needle, preventing it from aligning with the Earth's magnetic fields, causing inaccurate readings. The Earth's natural magnetic forces are considerably weak, measuring at 0.5 gauss and magnetic fields from household electronics can easily exceed it, overpowering the compass needle. Exposure to strong magnets, or magnetic interference can sometimes cause the magnetic poles of the compass needle to differ or even reverse. Avoid iron rich deposits when using
6497-401: The night of 6–7 August, she lost sight of the convoy in the darkness. After sunrise on 7 August 1918, she followed the expected track of the convoy, expecting to catch up with it. On the afternoon of 7 August, she sighted ships ahead which she assumed belonged to the convoy she was escorting. After following the ships for 15 minutes, she realized that they did not belong to her convoy and that she
6586-534: The north end of the needle are often marked with phosphorescent , photoluminescent , or self-luminous materials to enable the compass to be read at night or in poor light. As the compass fill liquid is noncompressible under pressure, many ordinary liquid-filled compasses will operate accurately underwater to considerable depths. Many modern compasses incorporate a baseplate and protractor tool, and are referred to variously as " orienteering ", "baseplate", "map compass" or "protractor" designs. This type of compass uses
6675-400: The pressure hull into the forward battery compartment (EB design), or the control room (Lake design). When retracted the circular gun shield formed the top of the cylinder with only the barrel of the gun protruding above deck. The Lake design retained Simon Lake's trademark amidships diving planes, theoretically used to enable zero-angle (a.k.a. even-keel) diving. This was a marked contrast to
6764-464: The principle of electromagnetic induction , with the Earth's magnetic field acting as the induction field for an electric generator , the measurable output of which varies depending on orientation . Small electronic compasses ( eCompasses ) found in clocks, mobile phones , and other electronic devices are solid-state microelectromechanical systems (MEMS) compasses, usually built out of two or three magnetic field sensors that provide data for
6853-430: The propellers) controlling the boat's angle while submerged. The Lake design also had a spindle shaped hull, but the rudder was ventrally mounted under the flat shovel-shaped stern with the propeller shafts also exiting the hull ventrally. The EB design retained the semi-hemispherical rotating bow cap that covered the four 18-inch diameter torpedo tubes . Although a common features on the EB design, this would prove to be
6942-401: The reception of electronic signals. GPS receivers using two or more antennae mounted separately and blending the data with an inertial motion unit (IMU) can now achieve 0.02° in heading accuracy and have startup times in seconds rather than hours for gyrocompass systems. The devices accurately determine the positions (latitudes, longitudes and altitude) of the antennae on the Earth, from which
7031-480: The ship and crew." In his report of the affair to United States Secretary of the Navy Josephus Daniels , O-6 ′s submarine division commander wrote, "It is believed that recognition should be made of the exceedingly efficient gunnery work of the merchant vessel in question, in that she got on so quickly, and held a difficult target under the circumstances of possible enemy attack." Jason at first
7120-559: The surviving EB design boats were decommissioned into reserve status in 1931. The harsh economics of the Great Depression prevented proper pre-layup maintenance, and very little if any work was done on the boats during the nine years they laid in reserve at the Philadelphia Navy Yard . Eight of the boats ( O-1 had been scrapped in 1938) were refitted and recommissioned in 1941 to serve as training boats based at
7209-479: 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.e. the direction in which its nose is pointing. 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
7298-407: 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. The ship is swung , that is rotated about
7387-487: Was commissioned at Boston , Massachusetts, on 12 June 1918, with Lieutenant Carroll Q. Wright in command. The United States had entered World War I by the time O-6 was commissioned, and she operated from Philadelphia , Pennsylvania , on coastal patrol along the United States East Coast , hunting Imperial German Navy U-boats from Cape Cod , Massachusetts, to Key West , Florida . O-6
7476-618: Was adopted by the former Warsaw Pact countries, e.g. , the Soviet Union, East Germany , etc., 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. Most manufacturers balance their compass needles for one of five zones, ranging from zone 1, covering most of
7565-617: Was discovered. O-4 suffered minor damage caused by shell splinters. The O-3 to O-10 formed part of the twenty-strong submarine force that left Newport, Rhode Island on 2 November 1918 for the Azores , but the task force was recalled after the Armistice was signed nine days later. The Lake design boats ( O-11 through O-16 ), built by the Lake Torpedo Boat Company and Craig Shipbuilding , suffered from electrical, structural, and mechanical problems. O-11
7654-445: Was immediately sent to the Philadelphia Navy Yard for a five-month overhaul. In October 1918, O-13 sank the patrol boat Mary Alice in a collision while she ( O-13 ) was submerged. O-15 also underwent a refit but was sent into reserve soon after before she went into service at Coco Solo in the Panama Canal Zone . This also involved another overhaul. O-16 also underwent a refit soon after commissioning and later suffered
7743-611: Was in fact following a convoy of 28 cargo ships . At 15:00, when she was about to turn away and head for port at the Delaware Breakwater in accordance with her orders, the last ship in the convoy, the American armed cargo ship SS Jason , which was slightly behind the rest of the convoy's ships, sighted her and mistook her for a German submarine with a mast and sail set. U.S. Navy gunners aboard Jason opened fire on O-6 with Jason ′s 5-inch (127 mm) gun at
7832-484: Was misidentified as a British merchant ship, but her actual identity later was established. Her gun crew had fired with great accuracy at long range, and the commander of her Navy gun crew was awarded a Navy Cross , the citation crediting Jason with an engagement with an enemy submarine. On 2 November 1918, O-6 departed Newport , Rhode Island , in a 20-submarine contingent bound for service in European waters. but
7921-546: Was the target in a friendly fire incident in the Atlantic Ocean in August 1918. On 6 August 1918, she departed Hampton Roads , Virginia , as one of the escorts for a convoy of five troop transports . With orders to escort the convoy for one day, she followed the convoy on the surface at a distance of 2 nautical miles (3.7 km; 2.3 mi), maintaining a speed of 12.5 knots (23.2 km/h; 14.4 mph). During
#608391