NSE refers to the difference between the aircraft's estimated position and actual position.
|
|
Estimated position by biometrics, Biom. Hum. et Anthropolol., 2006, 24, 3-4, 243–255.Boë, L.J. et al.
|
|
If it is not equal, then depending on the comparison, the remaining search space is reduced to the part before or after the estimated position. This method will only work if calculations on the size of differences between key values are sensible. By comparison, binary search always chooses the middle of the remaining search space, discarding one half or the other, depending on the comparison between the key found at the estimated position and the key sought — it does not require numerical values for the keys, just a total order on them. The remaining search space is reduced to the part before or after the estimated position.
|
|
If there is no positional information available, a new dead reckoning plot may start from an estimated position. In this case subsequent dead reckoning positions will have taken into account estimated set and drift. Dead reckoning positions are calculated at predetermined intervals, and are maintained between fixes. The duration of the interval varies.
|
|
The navigator was called to the bridge and he assumed that it was Loney Bluff on the southwest side of Quelpart Island in the East China Sea. There was nothing else visible eastwards and the position was within of the ship's estimated position. The stellar observation was finally worked out by 04:35 and it gave a position some north of the dead reckoning position, although it could not be confirmed. At 04:40 land was sighted ahead of the ship and the navigator ordered a turn to starboard to reverse course at 04:47. About 10 seconds after starting the turn a rock was spotted off the starboard bow and he attempted to reverse his turn, but Bedford ran aground on Samarang Reef, some north and west of her estimated position.
|
|
A course line is drawn on the aeronautical chart along with estimated positions at fixed intervals (say every ½ hour). Visual observations of ground features are used to obtain fixes. By comparing the fix and the estimated position corrections are made to the aircraft's heading and groundspeed. Dead reckoning is on the curriculum for VFR (visual flight rules - or basic level) pilots worldwide.
|
|
In 1977 a wreck was located off the mouth of the Xora River. Several investigations into this wreck, in particular under the leadership of Emlyn Brown, took place. It has proven particularly difficult to explain why the Waratah should be found so far to the north of her estimated position. Further attempts to locate the Waratah took place in 1983, 1989, 1991, 1995 and 1997.
|
|
Under a strict order of silence, the Yorkist army crept closer to the Lancastrians. During the night, neither commander spotted the opposing army, an event that proved crucial in the battle the next day. During the night, Warwick ordered his cannons to continually bombard the estimated position of the Yorkists' encampment. The Yorkists, however, had sneaked in close, and the Lancastrian artillery overshot their enemies.
|
|
While the destroyer steamed toward the estimated position of the sail, she searched for evidence of a submarine. After covering westward, she came upon an area marked by a number of small oil slicks. Wainwright chose the most promising of the slicks and dropped four depth charges. She then commenced another fruitless search which ended at midnight when she received orders to return to Queenstown.
|
|
This section of the English coast was hazardous, due to shallow waters, sharp rocks, and often-dense fog. By 10 pm, Suevic was encountering a strong south-westerly gale and severely reduced visibility due to showers of drizzling rain, the ship's officers were not able to fix their position using stellar navigation, so they intended to use instead the Lizard lighthouse on Lizard Point, Cornwall (known simply as "The Lizard"). At the ship's estimated position, the lighthouse should have been seen straight ahead, but instead at 10:15 pm it suddenly appeared out of the gloom close to the port side; due to miscalculations Suevic was ahead of her estimated position. Not realising the extent of the error, the Captain wrongly estimated that the lighthouse was several miles away, and pressed ahead at full speed, without using the sounding line to ensure they were not approaching the shore.
|
|
Then a trilateration technique can be used to calculate the estimated position of the device relative to the access points. The greatest challenges in the ToF approach consist in dealing with clock synchronization issues, noise, sampling artifacts and multipath channel effects. Some techniques use mathematical approaches to remove the need for clock synchronization. More recently, the Wi-Fi Round Trip Time standard has provided fine ToF ranging capabilities to WiFi.
|
|
October 1707. The dashed blue line shows the approximate route of Shovell's fleet from Cape Spartel to the Isles of Scilly. The filled circle shows the estimated position on 21 October, based on observations of latitude and soundings. The open circle shows the dead reckoning position of H.M.S. Orford when it hove to on 22 October, with the rest of the fleet, before they set off on the fatal last stage of the voyage.
|
|
A naval vessel uses a device called a pit sword (rodmeter), which uses two sensors on a metal rod to measure the electromagnetic variance caused by the ship moving through water. This change is then converted to ship's speed. Distance is determined by multiplying the speed and the time. This initial position can then be adjusted resulting in an estimated position by taking into account the current (known as set and drift in marine navigation).
|
|
The report from I-58 reached 22nd Air Flotilla Headquarters at 0315, and ten bombers of the Genzan Air Group were dispatched at 0600 to conduct a sector search for the ships. Many more planes, some armed with bombs and some with torpedoes, soon followed. The Genzan Air Group took off at 0755, the Kanoya Air Group at 0814, and the Mihoro Air Group at 0820. They were ordered to proceed to the best-estimated position of the ships.
|
|
If the position line indicates a location more than a few miles from the estimated position, more observations can be taken to restart the dead-reckoning track. In the event of equipment or electrical failure, taking sun lines a few times a day and advancing them by dead reckoning allows a vessel to get a crude running fix sufficient to return to port. One can also use the Moon, a planet, Polaris, or one of 57 other navigational stars to track celestial positioning.
|
|
Wracked with hits and unable to flee, Scharnhorst finally capsized and sank at 19:45 on 26 December, her propellers still turning, at an estimated position of . She was later identified and filmed at . Of her total complement of 1,968, only 36 were pulled from the frigid waters, 30 by Scorpion and six by Matchless. Neither Rear Admiral Bey nor Captain Hintze were among those rescued, although both were reported seen in the water after the ship sank, nor were any other officers.
|
|
After conducting additional glaciological studies, they were flown to the South Pole by the expedition Twin Otter on 16 February. They were only at the Pole for four hours, and their aircraft had not been equipped with survey gear. They were provided the use of a Spryte tracked vehicle, and they conducted a GPS survey to locate their estimated position of the tent to within 50 meters. They also detected a cavity in the snow near the presumed location of the tent.
|
|
The position response of 2-D tetra-lateral PSD obtained by formulae proposed in S. Cui's paper The position estimation results obtained by this set of formulae are simulated below. We assume the light spot is moving in steps in both directions and we plot position estimates on a 2-D plane. Thus a regular grid pattern should be obtained if the estimated position is perfectly linear with the true position. The performance is much better than the previous formulae.
|
|
Lunar laser ranging data for the Moon was added for the first time since DE403, significantly improving the lunar orbit and librations. Estimated position data from the Cassini spacecraft was included in the fit, improving the orbit of Saturn, but rigorous analysis of the data was deferred to a later date. DE418 covered the years 1899 to 2051, and JPL recommended not using it outside of that range due to minor inconsistencies which remained in the planets' masses due to time constraints. DE421 was released in 2008.
|
|
After the last sinking at the end of April, Leonardo da Vinci turned for home. On 22 May 1943, off the coast of Spain, it unwisely signalled its intention to head for Bordeaux on completion of its patrol. Its position having been fixed by direction-finding, on 23 May the destroyer and the frigate (both escorts to convoys WS-30 and KMF-15) subjected the submarine to an intense depth charge attack and sank it west of Vigo at an estimated position of . There were no survivors.
|
|
No. 9 Squadron began its attack six minutes after its sister squadron, 17 Lancasters dropping Tallboys. Like No. 617 Squadron, several aircraft from No. 9 Squadron made multiple bomb runs over Tromsø, one conducting five approaches before attacking. At least two of the No. 9 Squadron crews were able to take visual aim at Tirpitz through gaps in the cloud; the others aimed at the battleship's estimated position. Of the two No. 9 Squadron aircraft which did not bomb, one made two passes over Tromsø.
|
|
Modern practical navigators usually use celestial navigation in combination with satellite navigation to correct a dead reckoning track, that is, a course estimated from a vessel's position, course and speed. Using multiple methods helps the navigator detect errors, and simplifies procedures. When used this way, a navigator will from time to time measure the sun's altitude with a sextant, then compare that with a precalculated altitude based on the exact time and estimated position of the observation. On the chart, one will use the straight edge of a plotter to mark each position line.
|
|
Several Lancasters made more than one pass over the target area as their bomb aimers sought to locate Tirpitz or technical problems prevented their Tallboy from being dropped on the initial pass. Force B commenced its attack after the Tallboy Lancasters had completed theirs so that the shock waves from bomb explosions did not prematurely set off the JW mines. As none of the Force B aircrew were able to spot Tirpitz due to the smokescreen, they dropped the mines on the battleship's estimated position. These weapons did not cause any damage.
|
|
Titanic struck an iceberg at 11:40 PM that night and began sinking. Bride had woken up and begun getting ready to relieve Phillips when Captain Edward Smith entered the wireless room and told Phillips to prepare to send out a distress signal. Shortly after midnight, Captain Smith came in again and told them to send out the call for assistance and gave them Titanics estimated position. Phillips began sending out the distress signal, code CQD, while Bride took messages to Captain Smith about which ships were coming to Titanics assistance.
|
|
Despite the orders to bring their Tallboys back if visual bombing was not possible, almost all the bombers attacked; historian Patrick Bishop has written that this was due to an unwillingness to make the long return flight carrying a bomb. The first bombs were dropped at 7:49 am GMT, No. 617 Squadron leading the attack. Sixteen aircraft from the squadron released Tallboys aimed at Tirpitzs estimated position, several making multiple bomb runs before attacking. One of the three Lancasters which did not bomb made four runs over Tromsø before Tait gave its pilot permission to break off the attack.
|
|
The damaged tanker, supported by Royal Navy destroyers By 14 August Ohio was stopped with no hope of getting her engines going as she had been hit again whilst in tow of Penn. As Ledbury approached the estimated position of the tanker, the destroyer could find no sign of her. A little later, Commander Hill sighted gunfire ahead, and considering it to be Ohios escorts beating off reconnaissance snoops, the destroyer turned course towards the flashes on the horizon. As Ledbury approached Ohio, it was seen that the tanker was lying deep in the water, with a bent line of deck.
|
|
The distance the tide moves the boat along this line is computed by the tidal speed, and this gives an "estimated position" or EP (traditionally marked with a dot in a triangle). Tidal Indicator, Delaware River, Delaware c. 1897. At the time shown in the figure, the tide is feet above mean low water and is still falling, as indicated by pointing of the arrow. Indicator is powered by system of pulleys, cables and a float. (Report Of The Superintendent Of The Coast & Geodetic Survey Showing The Progress Of The Work During The Fiscal Year Ending With June 1897 (p.
|
|
One of the other cruisers, , checked her navigation when she spotted Ross Island at 05:00 the following morning and found that she was north and east of her estimated position. Heavy cloud cover had prevented all four ships from using celestial navigation to fix their position with any certainty; Kent was the only one that spotted a landmark clearly enough to determine her position.McBride, K.D., p. 22 Bedford got a partial star observation at 04:15, but the bridge crew was distracted by spotting land off the port side just seven minutes later and did not make the calculations until later.
|
|
The technique is to start at the estimated position of the target, at a distance above the bottom to provide the best view, and to swim in a cardinal direction a distance roughly equal to or slightly greater than the visibility range. The estimate of distance is commonly by kick counts, so using a whole number of kicks is necessary, and preferably a number which can be mentally accumulated by the diver. Call this distance n kicks, where n is usually 2, 4, 5, 10 or 20 as these are easy numbers to multiply mentally. The direction of turn may be clockwise or anticlockwise as best suits the search.
|
|
In the early 1960s the Soviet Union introduced the RBU-6000 and RBU-1000 anti- submarine rocket launchers, which worked on a similar principle to the Royal Navy's Hedgehog system of the Second World War, propelling small depth charges up to from a ship. However this meant that a ship would still be in range of the submarine's torpedoes and missiles, and depth charges were less accurate than homing torpedoes. In 1963 the US Navy introduced ASROC, a missile that flew to the estimated position of the target submarine, and then dropped a torpedo into the water to destroy it. The SS-N-14 was the Soviet response.
|
|
The navigators were unaware of the effect of the eastward flowing Gulf Stream, which must have hindered the fleet's progress – perhaps by as much as 30 km a day. The paymaster of the San Juan Bautista, Marcos de Aramburu, recorded a log of his progress from late August onwards, when the rest of the fleet was within sight. The inference from his observations is that his ship's estimated position as it turned for home was entirely wrong, some 480 km to the west: its real position lay in the east, perilously close to the coasts of Scotland and Ireland. This single deficiency "made the difference between safety and disaster".
|
|
In his book documenting the opening stages of the second Gulf War from his position embedded with the 1st Marine Reconnaissance Battalion, Evan Wright documents an incident during which, at night in the Iraqi desert, the marines observed the lights of a town approximately 40 kilometers away. These lights appeared to be moving and were suspected of belonging to a large combat force moving out to attack the marines. An airstrike was called in on the estimated position of the lights—estimated to be around 15 kilometers away—which resulted in no enemy assets being destroyed. It was later suggested by Major Shoup of the battalion that this misidentification was a result of autokinesis.
|
|
At the first estimated position of the South Pole, Amundsen declared "So we plant you, dear flag, on the South Pole, and give the plain on which it lies the name King Haakon VII's Plateau." Both the Norwegian and Fram's flag were planted. Due to the historical disputes over the claims of polar explorers prior to Amundsen's expedition, particularly the competing claims of Frederick Cook and Robert Peary to have reached the North Pole first, Amundsen took special care in making his polar observations. Approaching the Geographic South Pole (or North Pole) the meridians of longitude converge, eventually making a measure of longitude meaningless, as a degree of longitude will become smaller and smaller.
|
|
Hinks, Arthur Robert (1873–1945) (Archives in London and the M25 area) With the instruments he had, Amundsen estimated that he could determine the position of the pole by no better than a nautical mile (1.85 km). In order to ensure that there was no doubt that his expedition had in fact reached the South Pole, he determined to encircle, or "box" the pole. Three members of the expedition were sent out from the current estimated position of the pole, one continuing on the current expedition track and two at right angles to this direction. Each skier continued and erected a spare sledge runner with a black flag and note for Robert Falcon Scott when and if he arrived.
|
|
In November 2017, after the Disappearance of ARA San Juan, Grossi had the idea of reviewing the records of the hydro- acoustic stations of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) as an alternative to obtain clues about what happened with the submarine. He contacted Lassina Zerbo, the Executive Secretary of the CTBTO, and convinced him of doing such reviews. His efforts paid off: the agency subsequently reported on "an underwater impulse event" occurred near the last known position of the submarine by the listening posts on Ascension Island and Crozet Islands at . The remains of the ill-fated ship were found a year later, about twenty kilometers from the estimated position based on the cited records.
|
|
Interpolation search is an algorithm for searching for a key in an array that has been ordered by numerical values assigned to the keys (key values). It was first described by W. W. Peterson in 1957. Interpolation search resembles the method by which people search a telephone directory for a name (the key value by which the book's entries are ordered): in each step the algorithm calculates where in the remaining search space the sought item might be, based on the key values at the bounds of the search space and the value of the sought key, usually via a linear interpolation. The key value actually found at this estimated position is then compared to the key value being sought.
|
|
On 12 September 2006, Qantas Flight 68, Airbus A330 registration VH-QPA, from Hong Kong to Perth exhibited ADIRU problems but without causing any disruption to the flight. At and estimated position north of Learmonth, Western Australia, NAV IR1 FAULT then, 30 minutes later, NAV ADR 1 FAULT notifications were received on the ECAM identifying navigation system faults in Inertial Reference Unit 1, then in ADR 1 respectively. The crew reported to the later Qantas Flight 72 investigation involving the same airframe and ADIRU that they had received numerous warning and caution messages which changed too quickly to be dealt with. While investigating the problem, the crew noticed a weak and intermittent ADR 1 FAULT light and elected to switch off ADR 1, after which they experienced no further problems.
|
|
At 05.19 hrs on Tuesday 5 January 1993, Lerwick coastguard were advised that the tanker, Braer, en route from Bergen, Norway to Quebec, Canada, laden with 85,000 tonnes of Norwegian Gullfaks crude oil, had lost engine power but was in no immediate danger. Her estimated position then was 10 miles (19 km) south of Sumburgh Head (although the initial position given to the coastguards was off by five miles) and she was drifting in predominantly southwesterly winds of force 10–11. The coastguard alerted rescue helicopters from Sumburgh and RAF Lossiemouth, and made enquiries about the availability of local tugs. At the Coast Guard's suggestion, the master agreed that non-essential personnel should be removed from the vessel—14 of the 34 crew were taken off by the coastguard helicopter from Sumburgh at 08:25.
|
|
After some computations, referred to as sight reduction, this measurement is used to plot a line of position (LOP) on a navigational chart or plotting worksheet, the observer's position being somewhere on that line. (The LOP is actually a short segment of a very large circle on Earth that surrounds the GP of the observed celestial body. An observer located anywhere on the circumference of this circle on Earth, measuring the angle of the same celestial body above the horizon at that instant of time, would observe that body to be at the same angle above the horizon.) Sights on two celestial bodies give two such lines on the chart, intersecting at the observer's position (actually, the two circles would result in two points of intersection arising from sights on two stars described above, but one can be discarded since it will be far from the estimated position—see the figure at example below). Most navigators will use sights of three to five stars, if available, since that will result in only one common intersection and minimizes the chance of error.
|
|