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Ascension Technology

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Ascension Technology Corporation
Information
Industry Motion tracking, electromagnetic tracking, medical device components
Founded 1986
Founder Ernest B. Blood, Jack Scully
Headquarters Shelburne, Vermont, United States (2015); earlier the Burlington area and Milton, Vermont
Notable Personnel Ernest Blood (president), Jack Scully (vice president)
Products Bird, Flock of Birds, SpacePad, PC/BIRD, MotionStar, MotionStar Wireless, 3D-BIRD, laserBIRD, ReActor, miniBIRD, microBIRD, 3D Guidance (trakSTAR, driveBAY)
Parent Roper Industries (from 2012; operated as a division of NDI)
Website https://www.ascension-tech.com (now redirects to NDI)


Ascension Technology Corporation was a Vermont manufacturer of motion trackers, best known for its pulsed DC magnetic trackers such as the Bird and the Flock of Birds. It was founded in 1986 by engineer Ernest "Ernie" Blood and marketer Jack Scully, two former employees of Polhemus.[1] In the 1990s its trackers were used for head tracking in virtual reality games and research systems, for motion capture in film and television animation, and in flight simulators.[2] The company later moved into electromagnetic tracking of miniature sensors inside medical instruments. In 2012 Roper Industries bought its assets, and Ascension became part of Roper's subsidiary Northern Digital Inc. (NDI).[3][4]

Reviewed 11 October 2026. Founding, founders, GEC licence and 1990 SIGGRAPH sales (Burlington Free Press 2012 reprint), patent US 4,849,692, 1994-1995 Ascension releases and spec posts, SIGGRAPH exhibitor history, archived company pages and press-release lists 2000-2015, CAVE paper quote, Liquid Image, Maelstrom, ZGDV, Virtools, Iowa State and Imprint Interactive releases, Roper 10-Q, Vermont Business Magazine, Oaklins and NDI pages. About review dates.

History

Founding

Scully began his career in marketing at Polhemus in Colchester, Vermont, whose founder Bill Polhemus had led the team that developed the first magnetic sensor for tracking a pilot's head. Blood, a young engineer recently graduated from the University of Michigan, developed the first distortion-correction matrices, software that compensated for anomalies in the magnetic field caused by the metal of the cockpit. Both moved to McDonnell Douglas when it bought Polhemus in 1983. According to Scully, the two proposed non-military uses for the sensors, starting with a head-pointing communication aid for severely disabled people, and McDonnell Douglas fired them both in January 1986.[1]

Blood and Scully could not raise venture capital in Boston. Instead they licensed Blood's patented magnetic tracker to GEC Avionics in Rochester, England, for 1.3 million US dollars, which paid for the start of the business.[1] Blood's patent application, filed on 9 October 1986 and granted on 18 July 1989 as US 4,849,692, described measuring the position and orientation of a receiver relative to a transmitter with pulsed direct current magnetic fields. Each transmitting antenna is energized in turn and the Earth's field is subtracted, with the aim of accurate measurement near metal. Ascension Technology was the original assignee.[5]

Company materials from 2000 and 2015 and the 2012 newspaper profile give 1986 as the founding year.[1][6][7] One version of the company's "About" page from 2001 instead said that it was co-founded in 1989 by Ernest Blood and Jack Scully.[2]

Virtual reality and motion capture (1990s)

Ascension's press releases said its Bird trackers had been available since 1990.[8] Scully recalled that the partners next turned to the gaming industry and sold about 200,000 US dollars' worth of trackers for virtual reality games at the SIGGRAPH show in Dallas in 1990, games in which players wore a visor and had their heads tracked by Ascension sensors. He said those games never took off because a VR game cost 50,000 US dollars against 3,000 for Pac-Man, but the sales were enough for Ascension to build up its manufacturing.[1] The company exhibited at SIGGRAPH every year from 1991 to 2004. Its 1991 listing described a family of six-degree-of-freedom tracking devices: the Bird, which measured the position and orientation of a single small receiver, the Flock of Birds, which tracked multiple receivers over extended ranges, and the Big Bird transmitter, which extended the tracking range further, especially for virtual reality.[9]

In a July 1994 release the company said that Alias, Wavefront, Autodesk and Softimage all recommended the Flock for capturing the motion of live actors, and that an actor typically wore 10 to 15 Flock receivers. The release listed motion capture credits including R/Greenberg Associates' Shell Oil advertisements, Windlight's Weldon Pond pilot for CBS and Universal Studios' Jurassic Park tour.[10] A November 1994 release called the Flock the "workhorse" for capturing human motion for computer animation and added ILM, PDI, Sony and Colossal Pictures to the list of studios that had chosen it.[11] In December 1994 Ascension started a worldwide reseller program for the Flock, with Scully naming virtual reality and performance animation as emerging markets.[12]

In 1995 the company launched two lower-cost trackers aimed at VR. SpacePad, announced in May and June 1995, used a flat transmitting antenna made of wire loops that could be laid into a game pod, a wall or a seat. It was first shown at VR World '95, where it tracked the head and hands of players of Straylight's game 3D*XTC.[8] PC/BIRD, announced in December 1995, put the electronics of a Flock-class tracker on an ISA card for personal computers, at a list price of 2,475 US dollars.[13] MotionStar, a version of the Flock of Birds for character animation, was described in the same release as an established product.[13] At SIGGRAPH 1997 Ascension showed MotionStar Wireless, which it called "the world's first magnetic tracker without trailing cables".[9] The company said MotionStar Wireless was named Innovative Product of the Year by Computer Graphics World and Virtual Reality Product of the Year by CyberEdge Journal.[2]

Scully later said that one of the first animation units went to Industrial Light & Magic. As more competitors entered motion capture, Ascension's animation business declined, and medical instrument makers began to approach the company.[1]

Diversification (2000-2006)

By 2000 Ascension described itself as a company that made only motion trackers, sold for animation, simulation, virtual reality, medicine and biomechanics. It added an orientation-only tracker, the 3D-BIRD, and an optical tracker, the laserBIRD, both introduced at SIGGRAPH 2000.[6][9] The ReActor, an active optical (infrared) motion capture system, was previewed at the Game Developers Conference in March 2001.[14] In 2002 the Vermont Department of Economic Development and the U.S. Small Business Administration named Ascension, then based in Milton, Vermont, the state's Small Business Innovator of the Year.[15]

The company's release lists for 2003 and 2004 show work in several markets at once: ReActor 2 in May 2003, the medical microBIRD tracker in January 2004 (which received an R&D 100 Award that July), laserBIRD 2 in May 2004, laserBIRD head trackers for SAABTECH and Tiger helicopter simulators, and a "3D Guidance" device shown at the RSNA radiology meeting in November 2004.[16][17] In December 2006 it introduced a Hy-BIRD tracker at the I/ITSEC simulation conference.[18]

Medical focus and acquisition

The move into medicine began when two German companies used a 25 mm Ascension sensor on an ultrasound scan head to build three-dimensional images of unborn babies. That work drew the interest of GE and Siemens, which wanted sensors small enough to fit inside instruments. Ascension then shrank its sensors from 25 mm to 0.38 mm over about five years, with funding from the National Institutes of Health and DARPA. With GE Healthcare it developed ultrasound-guided needle tracking for procedures such as liver biopsies. By May 2012, Scully said, 70 percent of the company's business was medical.[1]

Roper Industries acquired the assets of Ascension Technology Corporation on 31 May 2012 and reported the business in its Medical and Scientific Imaging segment.[3] NDI, which Roper already owned, announced the deal in late July 2012 without disclosing terms. Ascension was to operate as a division of NDI and stay in Vermont, where it made its magnetic sensors; Scully became its managing director.[4] Oaklins, which advised the sellers, listed the transaction at 19 million US dollars.[19] In 2015 the company described itself as a maker of electromagnetic tracking systems for the medical OEM and medical simulation markets, based in Shelburne, Vermont, and best known for its 3D Guidance product suite, which included the driveBAY and trakSTAR systems.[7]

NDI's corporate history says the Ascension acquisition gave NDI a location in Shelburne, Vermont, and that its electromagnetic product range came to include the 3D Guidance line.[20] As of October 2026 the ascension-tech.com domain redirects to NDI's website, and NDI sells 3D Guidance with trakSTAR (desktop) and driveBAY (embedded) electronics units.[21]

Technology

Ascension's Bird-family magnetic trackers used pulsed DC fields, while Polhemus devices used AC magnetic fields.[13] In a 1995 explanation, the company said the Flock of Birds transmitter drove three orthogonal coils with square-wave pulses. Three orthogonal sensing coils in the receiver measured each pulse, and the nine measurements plus three background readings gave a six-degree-of-freedom solution. Ascension said this approach was less affected by eddy currents induced in nearby conductive metal. The same explanation listed the low-cost SpacePad among AC-based magnetic trackers.[22] Like other magnetic trackers, the systems needed no line of sight between transmitter and receiver, which the company presented as an advantage over trackers that had to keep a clear line of sight.[13]

Ascension published these Flock of Birds specifications in January 1995:[23]

Parameter Flock of Birds (1995 specification)
Translation range Plus or minus 3 ft (8 ft optional) in any direction
Angular range Plus or minus 180 degrees azimuth and roll, plus or minus 90 degrees elevation
Translation accuracy 0.1 in RMS
Angular accuracy 0.5 degrees RMS
Update rate Up to 144 measurements per second
Interface RS-232C up to 115,200 baud, or RS-422/485 up to 310,000 baud

Products

Product First documented Type Notes
Bird 1990 Pulsed DC magnetic tracker Company said Bird trackers were available from 1990[8]
Flock of Birds 1991 (SIGGRAPH listing) Pulsed DC magnetic tracker Multiple receivers; up to 29 receivers per system by 1994[9][10]
Big Bird 1991 (SIGGRAPH listing) Extended-range transmitter Extended the tracking range of the Bird family[9]
SpacePad May 1995 Low-cost magnetic tracker (AC-based) Flat wire-loop antenna; OEM pricing from 995 US dollars for one receiver[8][22]
PC/BIRD December 1995 Magnetic tracker on an ISA card List price 2,475 US dollars[13]
MotionStar By 1995 Magnetic motion capture system Flock-based system for character animation[13]
MotionStar Wireless 1997 (SIGGRAPH) Wireless magnetic motion capture Battery-powered backpack sent sensor data by radio to a base station[9][24]
3D-BIRD 2000 (SIGGRAPH) Orientation tracker For simulators and virtual environments[9][25]
laserBIRD 2000 (SIGGRAPH) Optical tracker For environments where magnetic, acoustic and inertial trackers could not be used[9][25]
ReActor 2001 Active optical (infrared) motion capture Previewed at GDC in March 2001; ReActor 2 in May 2003[14][16]
miniBIRD By 2001 Magnetic tracker with miniature sensors Sensors as small as 5 mm wide for medical imaging[25]
3D Navigator March 2004 Wireless magnetic tracker for CAVEs Head tracker and hand-held "Wanda" controller[26]
microBIRD January 2004 Miniature medical magnetic tracker R&D 100 Award, July 2004[17]
3D Guidance (trakSTAR, driveBAY) 2004 (RSNA device); suite by 2015 Medical electromagnetic tracking Sold by NDI as of 2026[17][7][21]

XR work

Ascension's trackers appear in several early virtual reality systems. The 1993 SIGGRAPH paper describing the CAVE at the University of Illinois at Chicago's Electronic Visualization Laboratory stated that the user's head and hand were tracked with "Polhemus or Ascension tethered electromagnetic sensors".[27] In March 2004 Ascension released 3D Navigator, a wireless tracker for CAVEs and large projection displays. Its press release quoted Carolina Cruz-Neira, then associate director of Iowa State University's virtual reality center, as saying that Ascension's improved wireless DC magnetic tracking was part of the success of the university's six-sided projection system.[26] In September 2004 Virtools added support for Ascension's laserBIRD, MotionStar, Nest of Birds, pciBIRD and Flock of Birds to its VR Pack software.[28]

Its low-cost trackers were used in location-based VR entertainment; in 2001 Ascension said SpacePad was used in VR games at location-based entertainment centers and arcades, including by Disney.[25] Liquid Image's QuickSilver VR entertainment system, based on Duke Nukem 3D and priced at 25,000 US dollars, included two MRG4 head-mounted displays, two PCs and two Ascension SpacePad trackers. The company's DukeTrak driver also supported the PC/BIRD.[29][30] In 2003 Ascension said that Maelstrom Virtual Productions of Leicester, England, used SpacePad in touring VR games: a penalty-kick soccer game with a tracked foot sensor and a cricket game, made for Channel 4 and the England and Wales Cricket Board, in which a real bat was tracked.[31]

The company also supplied trackers for medical augmented reality and VR therapy projects. In January 2003 Ascension and the Computer Graphics Center (ZGDV) in Darmstadt demonstrated the Medarpa medical augmented reality system at the Medicine Meets Virtual Reality conference. Medarpa used a semi-transparent display to overlay previously acquired medical images on the patient, and a miniBIRD 800 tracked the patient and the instruments.[32] In January 2007 Ascension said that Imprint Interactive of Seattle was using the Flock of Birds as the head tracker in VR exposure therapy simulations for post-traumatic stress disorder, built to support research by Hunter Hoffman of the University of Washington and by researchers of the Pacific Telehealth and Technology Hui at Tripler Army Medical Center in Honolulu.[18]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Dan D'Ambrosio (2012-05-03). "The end of open surgery: Ascension Technology in Milton is poised to ride the wave of minimally invasive techniques". Burlington Free Press (reprint hosted by Ascension Technology, archived). https://web.archive.org/web/20141201011632/http://www.ascension-tech.com:80/docs/2012/BurlingtonFreePress2012.pdf. Retrieved 2026-10-11.
  2. ↑ 2.0 2.1 2.2 "About Ascension Technology". Ascension Technology Corporation (archived). 2001. https://web.archive.org/web/20010424163703/http://www.ascension-tech.com:80/about/. Retrieved 2026-10-11.
  3. ↑ 3.0 3.1 "Roper Industries, Inc. Form 10-Q for the quarterly period ended June 30, 2012". U.S. Securities and Exchange Commission (EDGAR). Roper Industries. 2012. https://www.sec.gov/Archives/edgar/data/0000882835/000088283512000034/q2_2012-10q.htm. Retrieved 2026-10-11.
  4. ↑ 4.0 4.1 "Ascension Technology of Milton acquired by Roper Industries". Vermont Business Magazine. 2012-08-28. https://vermontbiz.com/node/188588. Retrieved 2026-10-11.
  5. ↑ Ernest B. Blood (1989-07-18). "US4849692A - Device for quantitatively measuring the relative position and orientation of two bodies in the presence of metals utilizing direct current magnetic fields". Google Patents. https://patents.google.com/patent/US4849692. Retrieved 2026-10-11.
  6. ↑ 6.0 6.1 "Company Background". Ascension Technology Corporation (archived). 2000. https://web.archive.org/web/20000929145626/http://www.ascension-tech.com:80/background/background.htm. Retrieved 2026-10-11.
  7. ↑ 7.0 7.1 7.2 "About Us". Ascension Technology Corp (archived). 2015. https://web.archive.org/web/20150327151908/http://www.ascension-tech.com:80/about-atc/. Retrieved 2026-10-11.
  8. ↑ 8.0 8.1 8.2 8.3 "New VR Tracker Blasts Off; Ascension Launches Revolutionary New Tracker for Virtual Reality Games/Experiences". sci.virtual-worlds archive. Ascension Technology Corporation. 1995-05-22. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/Ascension-SpacePad. Retrieved 2026-10-11.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 "Ascension Technology Corporation". ACM SIGGRAPH History Archive. ACM SIGGRAPH. https://history.siggraph.org/?p=183738. Retrieved 2026-10-11.
  10. ↑ 10.0 10.1 "Ascension's Flock of Birds Chosen for Motion Capture in Major Exhibits at SIGGRAPH '94". sci.virtual-worlds archive. Ascension Technology Corporation. 1994-07-08. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/Ascension-Flock. Retrieved 2026-10-11.
  11. ↑ "Ascension's Flock of Birds Chosen for Motion Capture Virtual Reality by Major Animation Studios and Movie Makers". sci.virtual-worlds archive. Ascension Technology Corporation. 1994-11-23. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/Ascension-Meckler95. Retrieved 2026-10-11.
  12. ↑ "Ascension Expands Distribution of Flock of Birds". sci.virtual-worlds archive. Ascension Technology Corporation. 1994-12-19. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/Ascension-12.19. Retrieved 2026-10-11.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 "ANNOUNCE: Ascension's Flock on an ISA card for PCs (PC/BIRD)". sci.virtual-worlds archive. Ascension Technology Corporation. 1995-12-14. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/PC-Bird-12.95. Retrieved 2026-10-11.
  14. ↑ 14.0 14.1 "Latest Press Releases". Ascension Technology Corporation (archived). 2001. https://web.archive.org/web/20010429195241/http://www.ascension-tech.com:80/news/press/. Retrieved 2026-10-11.
  15. ↑ "Ascension Technology Corp. Named 2002 Small Business Innovator of the Year". Ascension Technology Corporation (archived). 2002-11-04. https://web.archive.org/web/20030411012633/http://www.ascension-tech.com:80/news/press_110402.php. Retrieved 2026-10-11.
  16. ↑ 16.0 16.1 "Ascension Technology Press Releases - 2003". Ascension Technology Corporation (archived). 2004. https://web.archive.org/web/20041018024030/http://www.ascension-tech.com:80/news/press2003.php. Retrieved 2026-10-11.
  17. ↑ 17.0 17.1 17.2 "Ascension Technology Press Releases - 2004". Ascension Technology Corporation (archived). 2005. https://web.archive.org/web/20050216155938/http://ascension-tech.com:80/news/press2004.php. Retrieved 2026-10-11.
  18. ↑ 18.0 18.1 "Ascension's Flock of Birds at the Frontier with New Virtual Reality Applications". Ascension Technology Corporation (archived). 2007-01-19. https://web.archive.org/web/20070205073818/http://ascension-tech.com:80/news/press_011907.php. Retrieved 2026-10-11.
  19. ↑ "Ascension Technology Corporation has been acquired by Roper Industries, Inc.". Oaklins. 2012-07. https://oaklins.com/us/en/deals/29388. Retrieved 2026-10-11.
  20. ↑ "Our History". NDI (Northern Digital Inc.). https://www.ndigital.com/about/history/. Retrieved 2026-10-11.
  21. ↑ 21.0 21.1 "3D Guidance EM Tracking - Transmitters and Sensors". NDI (Northern Digital Inc.). https://www.ndigital.com/3dguidance/. Retrieved 2026-10-11.
  22. ↑ 22.0 22.1 Steve Work (1995-06-06). "Re: TECH: Tracking Person's Movement". sci.virtual-worlds archive. Ascension Technology Corporation. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/Ascension-Flock-of-Birds. Retrieved 2026-10-11.
  23. ↑ Steve Work (1995-01-06). "Re: TECH: Polhemus 3Space sensor". sci.virtual-worlds archive. Ascension Technology Corporation. https://ftp.ludd.ltu.se/pub/misc/virtual-worlds/commercial/Ascension/Ascension-Flock.txt. Retrieved 2026-10-11.
  24. ↑ "MotionStar Wireless". Ascension Technology Corporation (archived). 2000. https://web.archive.org/web/20000229222634/http://www.ascension-tech.com:80/products/mswireless/mswireless.htm. Retrieved 2026-10-11.
  25. ↑ 25.0 25.1 25.2 25.3 "Products". Ascension Technology Corporation (archived). 2001. https://web.archive.org/web/20010215021842/http://www.ascension-tech.com:80/products/. Retrieved 2026-10-11.
  26. ↑ 26.0 26.1 "Ascension Launches Advanced Wireless Tracking Solution for Immersive Environments". Ascension Technology Corporation (archived). 2004-03-18. https://web.archive.org/web/20040408032605/http://www.ascension-tech.com:80/news/press_031804.php. Retrieved 2026-10-11.
  27. ↑ Carolina Cruz-Neira, Daniel J. Sandin, Thomas A. DeFanti (1993). "Surround-Screen Projection-Based Virtual Reality: The Design and Implementation of the CAVE". Proceedings of SIGGRAPH '93. ACM. https://doi.org/10.1145/166117.166134. Retrieved 2026-10-11.
  28. ↑ "Ascension and Virtools Announce Strategic Virtual Reality Partnership". Ascension Technology Corporation (archived). 2004-09-10. https://web.archive.org/web/20041018030459/http://www.ascension-tech.com:80/news/press_091004.php. Retrieved 2026-10-11.
  29. ↑ "QuickSilver VR". Liquid Image Corporation (archived). 1999-01-27. https://web.archive.org/web/19990127091202/http://www.liquidimage.ca:80/qsvr.html. Retrieved 2026-10-11.
  30. ↑ "Duke Nukem 3D DukeTrak 6DoF Software Driver". Liquid Image Corporation (archived). 1999-04-17. https://web.archive.org/web/19990417052311/http://www.liquidimage.ca:80/dukedrv.html. Retrieved 2026-10-11.
  31. ↑ "Ascension's SpacePad Provides Tracking Solution for Innovative New Immersive Games". Ascension Technology Corporation (archived). 2003-06-17. https://web.archive.org/web/20030802141251/http://www.ascension-tech.com:80/news/press_061703.php. Retrieved 2026-10-11.
  32. ↑ "Ascension and ZGDV to Demo Medical Augmented Reality System at MMVR". Ascension Technology Corporation (archived). 2003-01-07. https://web.archive.org/web/20030203151243/http://www.ascension-tech.com:80/news/press_010703.php. Retrieved 2026-10-11.
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