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298:"gates" the measurements over a period of time and averages them out to produce a single measurement. The series of such numbers held in the buffer produce a strip of measurements similar to those held in the maps. The series of changes in the buffer is then compared with the values in the map, looking for areas where the changes in altitude are identical. This produces a location and direction. The guidance system can then use this information to correct the flight path of the missile.
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accuracy, however, is based on the accuracy of the radar mapping information, which is typically in the range of meters, and the ability of the processor to compare the altimeter data to the map quickly enough as the resolution increases. This generally limits first generation TERCOM systems to targets on the order of hundreds of meters, limiting them to the use of
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TERCOM systems have the advantage of offering accuracy that is not based on the length of the flight; an inertial system slowly drifts after a "fix", and its accuracy is lower for longer distances. TERCOM systems receive constant fixes during the flight, and thus do not have any drift. Their absolute
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as they are precise and cheap. Unfortunately, they rely on satellites. If the satellites are interfered with (e.g. destroyed) or if the satellite signal is interfered with (e.g. jammed), the satellite navigation system becomes inoperable. Therefore, the GPS/GLONASS/BeiDou/Galileo-based navigation is
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The massive improvements in memory and processing power from the 1950s, when these scene comparison systems were first invented, to the 1980s, when TERCOM was widely deployed, changed the nature of the problem considerably. Modern systems can store numerous images of a target as seen from different
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As a radar altimeter measures the distance between the missile and the terrain, not the absolute altitude compared to sea level, the important measure in the data is the change in altitude from square to square. The missile's radar altimeter feeds measurements into a small buffer that periodically
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The limited data storage and computing systems of the time meant that the entire route had to be pre-planned, including its launch point. If the missile was launched from an unexpected location or flew too far off-course, it would never fly over the features included in the maps, and would become
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Modern TERCOM systems use a different concept, based on the altitude of the ground over which missile flies and measure by radar altimeter of the missile and comparing that to measurements of prerecorded terrain altitude maps stored in missile avionics memory. TERCOM "maps" consist of a series of
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and produced a similar AM signal. By comparing the points along the scan where the brightness changed rapidly, which could be picked out easily by simple electronics, the system could compare the left-right path of the missile compared with that of the pathfinding aircraft. Errors between the two
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Due to the limited amount of memory available in mass storage devices of the 1960s and 70s, and their slow access times, the amount of terrain data that could be stored in a missile-sized package was far too small to encompass the entire flight. Instead, small patches of terrain information were
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During the cruise portion of the flight to the target, the accuracy of the system has to be enough only to avoid terrain features. This allows the maps to be a relatively low resolution in these areas. Only the portion of the map for the terminal approach has to be higher resolution, and would
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squares of a selected size. Using a smaller number of larger squares saves memory, at the cost of decreasing accuracy. A series of such maps are produced, typically from data from radar mapping satellites. When flying over water, contour maps are replaced by magnetic field maps.
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which could guide missiles in real time by using camera inputs to determine location. DSMAC was used in
Tomahawk Block II onward, and proved itself successfully during the first Gulf War. The system worked by comparing camera inputs during flight to maps computed from
258:. This mating resulted in a production contract in June 1954. ATRAN was difficult to jam and was not range-limited by line-of sight, but its range was restricted by the availability of radar maps. In time, it became possible to construct radar maps from
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directions, and often the imagery can be calculated using image synthesis techniques. Likewise, the complexity of the live imaging systems has been greatly reduced through the introduction of solid-state technologies like
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lost. The INS system can help, allowing it to fly to the general area of the first patch, but gross errors simply cannot be corrected. This made early TERCOM-based systems much less flexible than more modern systems like
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useful in a conflict with a technologically unsophisticated adversary. On the other hand, to be ready for a conflict with a technologically advanced adversary, one needs missiles equipped with TAINS and DSMAC.
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images. The DSMAC AI system computed contrast maps of images, which it then combined in a buffer and then averaged. It then compared the averages to stored maps computed beforehand by a large
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on the aircraft was set to a fixed angle and made horizontal scans of the land in front. The timing of the return signal indicated the range to the landform and produced an
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Newer
Russian cruise missiles, such as Kh-101 and Kh-555 are likely to have TERCOM navigation, but little information is available about these missiles
599:"Image Processing For Tomahawk Scene Matching". Johns Hopkins APL Technical Digest, Volume 15, Number 3. Geoffrey B. Irani and James P. Christ.
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taken by satellites or aircraft with information received from the onboard active radar regarding target topography, for terminal guidance.
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allows much larger areas of landscape contour data to be acquired for comparison with the stored contour data.
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In the missile, a similar radar produced the same signal. A second system scanned the frames of film against a
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signals drove corrections in the autopilot needed to bring the missile back onto its programmed flight path.
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of the terrain that is compared with measurements made during flight by an on-board
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CSS-N-8 Saccade (China) – it is unclear if this missile employs TERCOM navigation
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Yet another way to navigate a cruise missile is by using a
615:, Section 16.5.3 of Fundamentals of Naval Weapons Systems
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The cruise missiles that employ a TERCOM system include:
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stored and periodically used to update a conventional
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was the earliest known TERCOM system. In August 1952,
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initiated the mating of the
Goodyear ATRAN with the
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484:anti-ship & land attack cruise missile (China)
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398:digitized scene-mapping area correlator (DSMAC)
319:, for TERCOM-Aided Inertial Navigation System.
365:DSMAC, Digital Scene Matching Area Correlator
244:Automatic Terrain Recognition And Navigation
537:(anti-ship and land attack missile, Norway)
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141:, is a navigation system used primarily by
226:Learn how and when to remove this message
122:Learn how and when to remove this message
189:This section includes a list of general
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531:(Pakistan) air-launched cruise missile
446:Missiles that employ TERCOM navigation
360:Comparison with other guidance systems
543:(air-launched cruise missile, Turkey)
525:(Pakistan) land attack cruise missile
559:and cruise missile variants, Russia)
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60:adding citations to reliable sources
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195:it lacks sufficient corresponding
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456:Supersonic Low Altitude Missile
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557:short-range ballistic missile
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240:Goodyear Aircraft Corporation
439:satellite positioning system
371:Automatic target recognition
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629:November 18, 2001, at the
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494:AS-15 Kent (Soviet Union)
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172:Optical contour matching
135:Terrain contour matching
210:more precise citations.
167:Digital elevation model
624:Info at aeronautics.ru
350:digital elevation maps
656:Aerospace engineering
549:1/2/3 cruise missiles
651:Aircraft instruments
619:More info at fas.org
535:Naval Strike Missile
433:Satellite navigation
252:Air Materiel Command
56:improve this article
505:NATO reporting name
492:NATO reporting name
423:active radar homing
271:amplitude modulated
386:mainframe computer
354:side-looking radar
313:inertial platform
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49:verification
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511:Hyunmoo III
470:AGM-129 ACM
411:Pershing II
248:MGM-13 Mace
216:August 2024
208:introducing
161:Description
147:contour map
640:Categories
587:References
419:OTR-23 Oka
369:See also:
323:Advantages
275:35 mm film
191:references
165:See also:
112:April 2020
82:newspapers
503:or YJ-82
282:photocell
627:Archived
570:See also
547:HongNiao
421:used an
71:"TERCOM"
581:TERPROM
519:(China)
490:Granat
464:AGM-86B
458:project
409:MGM-31
242:ATRAN (
204:improve
96:scholar
193:, but
139:TERCOM
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529:Ra'ad
523:Babur
517:DH-10
501:C-802
488:Kh-55
482:C-602
317:TAINS
306:TAINS
267:radar
137:, or
103:JSTOR
89:books
18:DSMAC
394:CCDs
238:The
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343:GPS
58:by
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