Synthetic vision system
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A synthetic vision system (SVS) is an aircraft display system that shows the pilot a computer-generated picture of the terrain, obstacles and airports outside the aircraft, drawn from onboard databases and the aircraft's own position and attitude rather than from a camera or other imaging sensor. The U.S. Federal Aviation Administration (FAA) defines synthetic vision as "a computer-generated image of the external scene topography from the perspective of the flightdeck that is derived from aircraft attitude, high-precision navigation solution, and database of terrain, obstacles and relevant cultural features", and a synthetic vision system as "an electronic means to display a synthetic vision image of the external scene topography to the flightcrew".[1] The aim is to give the crew the visual cues they would have on a clear day, whatever the actual weather or lighting.[2]
FAA-certified synthetic vision displays were available in business jets and in general aviation avionics by 2008,[3][4] and in 2011 NASA researchers described synthetic and enhanced vision as "emerging as standard equipage on today's flight deck".[5] FAA guidance covers synthetic vision on head-down primary and secondary flight displays as well as on head-up displays.[6][7] On a head-up display or a head-tracked head-worn display, the scene can be drawn conformally, lined up with the pilot's real view of the world; the FAA requires that synthetic vision on a head-up display not give a distorted, non-conformal view of the external scene.[6] NASA researchers were testing head-worn synthetic vision displays by 2007,[8] and a 2023 German Aerospace Center (DLR) study by Johannes Maria Ernst built a simulated, fully virtual helicopter cockpit in which a non-see-through virtual reality headset replaces the pilot's view of the outside world.[9] Ernst notes that augmented reality "has long since become an everyday occurrence on modern flight decks, for example in the form of head-up displays".[9]
Definition and components
In FAA guidance, synthetic vision draws its picture "relative to terrain and airport within the limits of the navigation source capabilities (position, altitude, heading, track, and the database limitations)". The FAA lists four elements of an installed SVS: the display, the system interface, a database of terrain and obstacles, and the sources that provide the aircraft's altitude, attitude and position.[7] NASA describes the display as one in which the view of the outside world comes from "melding computer-generated external topography scenes from on-board databases with flight display symbologies and other information obtained from on-board sensors, data links, and navigation systems". Position normally comes from GPS, possibly with augmentation such as the Wide Area Augmentation System, blended with an inertial navigation or inertial reference system.[2] Honeywell, for example, describes its SmartView SVS as synthesizing "flight information from multiple onboard databases, GPS and inertial reference systems into a complete, easy-to-understand 3-D rendering of the forward terrain".[10]
The FAA distinguishes two viewpoints. An egocentric display shows the scene from the flight deck, usually on the primary flight display; an exocentric display shows it from a point outside the aircraft, "like a 'bird's eye' view of a moving map display", usually on a secondary display.[7] Moving objects that are not in the stored database, such as other traffic, can be added from surveillance sources such as TCAS and ADS-B, and unmapped obstacles from onboard sensors such as weather radar.[2]
Terrain databases
Synthetic vision terrain is usually referenced to Digital Terrain Elevation Data (DTED), from which a digital elevation model (DEM) is built for rendering. AC 20-167A gives the three DTED levels for reference:[7]
| DTED level | Post spacing | Nominal ground distance |
|---|---|---|
| Level 0 | 30 arc seconds | about 1 kilometer |
| Level 1 | 3 arc seconds | about 100 meters |
| Level 2 | 1 arc second | about 30 meters |
According to the same circular, NASA experiments found that a 30 arc second database "rounds off" peaks and fills in valleys, so peaks look less hazardous than they are. Pilots preferred 1 and 3 arc second terrain, but even a 30 arc second display gave more situation awareness than conventional instruments, and the FAA had treated 30 arc seconds as the minimum. AC 20-167A said new systems "should meet 15 arc sec or better", and the current AC 20-185A keeps the recommendation as 15 equatorial arc-seconds or better.[7][6] NASA's review cites reliable GPS positioning and precise digital terrain models, including data from the February 2000 Shuttle Radar Topography Mission, as what made the approach potentially capable of all-weather performance at low cost.[2]
Relationship to enhanced and combined vision
Synthetic vision is one of several aircraft vision systems that regulators group together. The difference is where the picture comes from: a database for synthetic vision, an imaging sensor for enhanced vision, or both.[7][9]
| System | Image source | Notes |
|---|---|---|
| Synthetic vision system (SVS) | Stored terrain, obstacle and airport databases plus aircraft position and attitude | Range is not limited by weather, but the picture is only as current and accurate as the database and navigation solution[2][9] |
| Enhanced vision system (EVS) | Imaging sensors such as forward-looking infrared, millimeter wave radiometry or radar, or low-light image intensification | Gives situation awareness but no credit toward operations under 14 CFR 91.176 (a) and (b)[7] |
| Enhanced flight vision system (EFVS) | Imaging sensors, shown with flight information and symbology on a head-up display or equivalent display | Defined in 14 CFR 1.1; the head-up presentation is required by 14 CFR 91.176[7] |
| Combined vision system (CVS) | Synthetic vision combined with EVS or EFVS imagery on one display | In the FAA's example, an approach shows mostly the synthetic picture, then transitions smoothly to sensor imagery near the runway[7] |
| Synthetic vision guidance system (SVGS) | SVS scene plus extra symbology, integrity monitors and annunciations | Supports special authorization Category I ILS approaches to 150 ft height above touchdown[6] |
| Aircraft state awareness SVS (ASA-SVS) | Perspective synthetic terrain with overlaid primary flight display symbology | Intended to reduce the risk of loss of control in flight[6] |
Each source has weaknesses. A database shows the world as it was when the data were collected, and a synthetic image is only correctly placed if position and attitude are correct; a sensor sees current conditions but has limited range, and its picture depends on the atmosphere.[9] NASA notes that sensor images are monochrome and that high-frequency radars and infrared sensors lose range in heavy rain and some fog types, while synthetic displays are "unlimited in range" and "unaffected by atmospheric conditions".[2]
History
Early display research
Rudimentary perspective displays of the airport environment, showing only a runway outline and a horizon line, were called "contact analog" displays in 1969 flight display research. Early versions were limited to line segments drawn by stroke generators; raster graphics later allowed filled polygons and "pictorial displays" of airports and surrounding terrain, and texturing, in some concepts with aerial or satellite photography, gave more realistic scenes. NASA's review notes that the term itself was used loosely for years: an FAA flight test program in 1992 called the "Synthetic Vision Technology Demonstration" actually evaluated millimeter wave and infrared sensors, which would now be called enhanced vision. The research community later settled on "synthetic vision" for views rendered from a geospatial database and "enhanced vision" for imaging sensor displays.[2]
According to NASA, a precursor study to its synthetic vision program, performed in 1994, found that pilots flying approaches with synthetic or enhanced vision imagery could not reliably spot navigation errors, database errors or runway incursions on their own, and concluded that "SVS concepts should not be implemented without incorporating image processing decision aiding".[2]
NASA Synthetic Vision Systems Project
NASA's Synthetic Vision Systems Project, part of its Aviation Safety Program, ran officially from 1 October 1999 to 30 September 2005, with planning workshops starting in 1997. Its aim was to remove low visibility as a cause of accidents for transport aircraft, business jets, rotorcraft and general aviation. NASA cited Boeing data showing that over 30 percent of fatal commercial accidents worldwide were controlled flight into terrain. Industry partners under cooperative research agreements included Rockwell Collins, Jeppesen, Boeing, BAE Systems, Avidyne and Rannoch, and Gulfstream was among the contractors.[2]
| Date | Location | Aircraft | Focus |
|---|---|---|---|
| September 1999 | Asheville, North Carolina | USAF Total In-Flight Simulator (Convair 580) | SVS primary flight display compared side by side with a color TV camera view |
| October 2000 | Dallas/Fort Worth, Texas | NASA Langley ARIES Boeing 757-200 | Night operations with SVS head-up and head-down displays; runway incursion prevention |
| October 2001 | Eagle County, Colorado | NASA Langley ARIES Boeing 757 | Day operations with SVS head-up and head-down displays compared with conventional displays |
| August-October 2002 | Newport News and Roanoke, Virginia | NASA Langley Cessna 206-H | Terrain texture and DEM resolution variations |
| July-August 2003 | California and Nevada | NASA Ames DC-8 | Database integrity monitoring and LiDAR elevation data collection |
| July-September 2004 | Reno, Nevada, and Wallops, Virginia | Gulfstream G-V | Integrated SVS for flight and surface operations |
| August-September 2005 | Roanoke, Virginia | NASA Langley Cessna 206-H | Whether SVS displays could make instrument conditions resemble visual flight |
Flight tests under direct NASA control, from NASA/TP-2008-215130.[2]
The project also folded in a "pathway" or "highway in the sky" display that draws the intended flight path as a 3D tunnel over the synthetic terrain, and a Runway Incursion Prevention System for airport surface operations.[2]
Certification and adoption
In February 2008, Aviation Today reported that the FAA had approved Gulfstream's Synthetic Vision-Primary Flight Display (SV-PFD) during late 2007 and early 2008 for the G350, G450, G500 and G550 business jets. The SV-PFD shows three-dimensional color terrain using data from Honeywell's Enhanced Ground Proximity Warning System, and the magazine described Gulfstream as the first Part 25 aircraft manufacturer to receive FAA certification for a synthetic vision system.[3] Garmin's Synthetic Vision Technology (SVT) for the G1000 integrated flight deck was certified in 2008; Garmin later said it could be installed on nearly every G1000 system ever delivered through a software update, with no change to the equipment configuration, provided the system had been kept up to date.[4] By 2013, Avionics magazine reported that Rockwell Collins was the only SVS supplier to have certified synthetic vision on a head-up display, on the Bombardier Global Express platform.[11]
FAA guidance for these systems has been revised several times:
| Document | Date | Scope |
|---|---|---|
| AC 20-167 | 22 June 2010 | Airworthiness approval of EVS, SVS, CVS and EFVS equipment[7] |
| AC 20-185 | 17 December 2015 | Airworthiness approval of synthetic vision guidance systems[6] |
| AC 20-167A | 6 December 2016 | Replaced AC 20-167; referenced in the preamble of the December 2016 EFVS final rule[7][1] |
| AC 20-185A | 27 January 2021 | Replaced AC 20-185; consolidated all synthetic vision guidance (SVS, SVGS and the new ASA-SVS)[6] |
| AC 20-167B | 8 September 2025 | Covers EVS, EFVS and CVS only; SVS material moved to AC 20-185A[1] |
Head-worn and helmet-mounted synthetic vision
NASA identified the two major limitations of head-up displays for ground operations as their monochrome form and their "limited, fixed field of regard".[8] Because a synthetic scene is rendered from a virtual camera that software can point anywhere, a synthetic vision image on a head-worn display coupled to a head tracker can follow the pilot's head with an "unlimited field-of-regard", something a fixed imaging sensor cannot do without multiple tiled sensors or a turret.[8][5]
NASA research
NASA Langley tested this idea for airport taxi operations in two simulator experiments reported in 2007. The head-worn display was an 800 x 600 pixel, full-color, see-through display refreshing at 60 Hz, worn by the captain over the right eye so it could be seen by glancing up, with an optical head tracker. Sixteen airline crews took part in the first experiment and twelve in the second, taxiing a simulated Boeing 757 at Chicago O'Hare. The fully integrated head-worn concept, which combined a conformal 3D synthetic view of the airport surface with taxi route and guidance information, gave better path performance than paper charts alone. Pilots rated it the same as a head-up display concept for situation awareness and workload, but there were more than twice as many taxi incursion events with the head-up display as with the head-worn display.[8]
A 2011 follow-up evaluated a head-tracked head-worn display with synthetic and enhanced vision for closely spaced parallel approaches to San Francisco and for taxiing at O'Hare. In low visibility, pilots rated the head-worn display as equivalent, for situation awareness and mental workload, to flying with an unlimited out-the-window view.[5] A 2015 NASA review of three decades of its helmet-mounted and head-worn display work concluded that a small, sunglasses-type form factor would be acceptable to commercial pilots, and that "HUD equivalence" was the likely economic route to bringing head-worn displays onto commercial and business flight decks.[12]
Certified head-wearable displays
In July 2015, Elbit Systems and ATR agreed to offer the ClearVision enhanced flight vision system with the SKYLENS wearable display on ATR 42-600 and 72-600 turboprops, with SKYLENS replacing the conventional head-up display in that configuration.[13] In March 2020, AIN reported that EASA had approved Universal Avionics' ClearVision system with the SkyLens head-wearable display on the ATR 72/42.[14] In December 2023, Universal Avionics announced an FAA supplemental type certificate for the system on the Boeing 737NG, marketed as AerAware through a partnership with AerSale, with SkyLens displays for both pilots. The company said the system brings synthetic and enhanced vision together in a user-controlled combined vision system and gives "a 3D and 180-degree panoramic view of the outside world showing terrain, obstacles, airports, and runways", and that the display's "unlimited field of regard" lets pilots turn their heads while keeping flight information in view.[15]
Helicopters and virtual cockpits
Helicopter crews flying close to the ground in degraded visual environments such as brownout are another target.[9] Patrizia Knabl and Helmut Többen published symbology for a 3D conformal synthetic vision helmet-mounted display for such operations in 2013.[16] A 2023 DLR dissertation by Johannes Maria Ernst proposed a "virtual cockpit continuum" running from a conventional flight deck, through partially virtual cockpits in which see-through head-mounted displays add symbology to the real view, to a fully virtual cockpit in which a non-see-through head-mounted display replaces both the out-the-window view and the instruments. In pilot studies for offshore helicopter operations, a fully virtual cockpit with an enhanced exocentric view improved spatial awareness and hover precision in confined areas, and one study replaced the real sea with a synthetic ocean surface designed to give better visual cues. The DLR simulator's head-mounted display graphics were built in Unity and had been used with the Oculus Rift CV1, HTC Vive Pro and Meta 2 headsets; the see-through virtual cockpit symbology was evaluated with the flight-certified Elbit JedEye helmet-mounted display, which at the time ran on separate legacy software. Ernst notes that a fully virtual cockpit depends entirely on its data sources: anything the sensors and databases do not capture, the pilot cannot see.[9]
Research findings
Human factors studies have compared synthetic vision with conventional flight instruments. In a University of Iowa simulator study published in 2004, 12 pilots hand-flew fairly difficult approaches into Eagle County, Colorado; the authors reported that the synthetic vision displays were "superior to the conventional displays for the majority of the measures", which covered flight technical error, situation awareness, workload and eye movements.[17] Alexander, Wickens and Hardy found in two simulator experiments that tunnel-in-the-sky guidance on a synthetic vision display gave better path tracking and lower workload than a "follow-me aircraft" symbol, that making the tunnel brighter degraded traffic awareness through clutter and attentional tunneling, and that a 60 degree geometric field of view generally beat 30 degrees, while display size had no effect.[18]
In an appendix on small-airplane (part 23) systems used only for situation awareness, the 2016 FAA guidance warned that "synthetic vision may be so compelling that pilots may try to use it beyond the intended function". It noted that current systems may lack the depth and distance cues needed for terrain avoidance, that a small display can compress the scene and mislead altitude and range judgments, and that GPS, database and barometric altimetry errors add up. It recommended a terrain warning function, a complementary plan-view map, and an audio callout near approach minimums, since pilots may "see" the runway on the synthetic display and continue below minimums.[7] For helicopter displays, Ernst reviews work showing that terrain database registration errors and aircraft position inaccuracy can misplace conformal symbology, and describes fusing database terrain with real-time lidar or radar data as the common way to resolve database inaccuracies and add hazards that are not in the database.[9]
Operational status
Current FAA guidance describes a basic SVS as providing "only a supplemental view of the external scene" and states that it "cannot be used in lieu of natural vision".[6] Operational credit requires a more capable system. AC 20-185A covers a synthetic vision guidance system meeting RTCA DO-359 (May 2015) for special authorization Category I ILS approaches down to 150 ft height above touchdown, with separate operational approval from FAA Flight Standards. The same circular added the aircraft state awareness SVS described in RTCA DO-371, intended for full-time display on the head-down primary flight display; DO-371 also covers head-up presentation as a supplement, but the FAA says its standards are not sufficient to replace the head-down version with a head-up one.[6]
See also
References
- ↑ 1.0 1.1 1.2 "AC 20-167B: Airworthiness Approval of Enhanced Vision System, Enhanced Flight Vision System, and Combined Vision System Equipment". Advisory Circular. Federal Aviation Administration. 2025-09-08. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-167B.pdf. Retrieved 2026-10-06.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Russell V. Parrish, Randall E. Bailey, Lynda J. Kramer, Denise R. Jones, Steven D. Young, Jarvis J. Arthur III, Lawrence J. Prinzel III, Louis J. Glaab, Steven D. Harrah (2008-05). "Aspects of Synthetic Vision Display Systems and the Best Practices of the NASA's SVS Project (NASA/TP-2008-215130)". NASA Technical Reports Server. NASA Langley Research Center. https://ntrs.nasa.gov/api/citations/20080018605/downloads/20080018605.pdf. Retrieved 2026-10-06.
- ↑ 3.0 3.1 Tish Drake (2008-02-05). "FAA Certifies Gulfstream Synthetic Vision System". Aviation Today. https://www.aviationtoday.com/2008/02/05/faa-certifies-gulfstream-synthetic-vision-system/. Retrieved 2026-10-06.
- ↑ 4.0 4.1 "Garmin Celebrates the Tenth Anniversary of G1000". Garmin Newsroom. Garmin. 2014-06-25. https://www.garmin.com/en-US/newsroom/press-release/aviation/2014-garmin-celebrates-the-tenth-anniversary-of-g1000/. Retrieved 2026-10-06.
- ↑ 5.0 5.1 5.2 Jarvis J. Arthur III, Lawrence J. Prinzel III, Steven P. Williams, Randall E. Bailey, Kevin J. Shelton, R. Mike Norman (2011-05). "Enhanced/synthetic vision and head-worn display technologies for terminal maneuvering area NextGen operations". Proceedings of SPIE, vol. 8042, Display Technologies and Applications for Defense, Security, and Avionics V; and Enhanced and Synthetic Vision 2011, 80420Q. doi:10.1117/12.883036. https://ntrs.nasa.gov/api/citations/20110011177/downloads/20110011177.pdf. Retrieved 2026-10-06.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 "AC 20-185A: Airworthiness Approval of Synthetic Vision Systems, Synthetic Vision Guidance Systems and Aircraft State Awareness Synthetic Vision Systems". Advisory Circular. Federal Aviation Administration. 2021-01-27. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-185A.pdf. Retrieved 2026-10-06.
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 "AC 20-167A: Airworthiness Approval of Enhanced Vision System, Synthetic Vision System, Combined Vision System, and Enhanced Flight Vision System Equipment". Advisory Circular. Federal Aviation Administration. 2016-12-06. https://www.faa.gov/documentlibrary/media/advisory_circular/ac_20-167a.pdf. Retrieved 2026-10-06.
- ↑ 8.0 8.1 8.2 8.3 J. J. Arthur III, Lawrence Prinzel III, Kevin Shelton, Lynda J. Kramer, Steven P. Williams, Randall E. Bailey, Robert M. Norman (2007-04). "Design and testing of an unlimited field-of-regard synthetic vision head-worn display for commercial aircraft surface operations". Proceedings of SPIE, vol. 6559, Enhanced and Synthetic Vision 2007, 65590E. doi:10.1117/12.719695. https://ntrs.nasa.gov/api/citations/20070018771/downloads/20070018771.pdf. Retrieved 2026-10-06.
- ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 Johannes Maria Ernst (2023). "Creating a Virtual Helicopter Cockpit with an Immersive Head-Mounted Display (DLR-Forschungsbericht 2023-21)". Deutsches Zentrum für Luft- und Raumfahrt, Institut für Flugführung, Braunschweig. doi:10.57676/t3x1-2x64. https://elib.dlr.de/200023/1/DLR_FB_2023_21_JohannesMariaErnst_VirtualCockpit_compressed.pdf. Retrieved 2026-10-06.
- ↑ "SmartView Synthetic Vision System (SVS)". Honeywell Aerospace. Honeywell. https://www.honeywellaerospace.com/us/en/products-and-services/products/cabin-and-cockpit/avionics/synthetic-vision-systems/smartview-synthetic-vision-system-svs. Retrieved 2026-10-06.
- ↑ Ed McKenna (2013-02-01). "Product Focus: Synthetic Vision Systems". Avionics (Aviation Today). https://www.aviationtoday.com/2013/02/01/product-focus-synthetic-vision-systems/. Retrieved 2026-10-06.
- ↑ Jarvis J. Arthur III, Randall E. Bailey, Steven P. Williams, Lawrence J. Prinzel III, Kevin J. Shelton, Denise R. Jones, Vincent Houston (2015-04). "A Review of Head-Worn Display Research at NASA Langley Research Center". NASA Technical Reports Server (SPIE Defense, Security, and Sensing 2015). https://ntrs.nasa.gov/citations/20150010966. Retrieved 2026-10-06.
- ↑ "Elbit Systems and ATR Sign an Agreement for the Integration of ClearVision EFVS with the New SKYLENS Wearable Display Onboard ATR -600s Aircraft". ATR. ATR and Elbit Systems. 2015-07-06. https://www.atr-aircraft.com/wp-content/uploads/2020/07/atr_elbit_en_2__1339.pdf. Retrieved 2026-10-06.
- ↑ Matt Thurber (2020-03-18). "Head-wearable Display Obtains First Certification". AIN Online. https://www.ainonline.com/aviation-news/business-aviation/2020-03-18/head-wearable-display-obtains-first-certification. Retrieved 2026-10-06.
- ↑ "Universal Avionics Receives FAA Approval for ClearVision under AerAware on the Boeing 737NG". Universal Avionics. 2023-12-12. https://universalavionics.com/press-releases/universal-avionics-receives-faa-approval-for-clearvision-under-aeraware-on-the-boeing-737ng. Retrieved 2026-10-06.
- ↑ Patrizia Knabl, Helmut Többen (2013). "Symbology Development for a 3D Conformal Synthetic Vision Helmet-Mounted Display for Helicopter Operations in Degraded Visual Environment". Engineering Psychology and Cognitive Ergonomics (Lecture Notes in Computer Science), Springer, pp. 232-241. doi:10.1007/978-3-642-39360-0_26. https://doi.org/10.1007/978-3-642-39360-0_26. Retrieved 2026-10-06.
- ↑ Thomas Schnell, Yongjin Kwon, Sohel Merchant, Timothy Etherington (2004-02). "Improved Flight Technical Performance in Flight Decks Equipped With Synthetic Vision Information System Displays". The International Journal of Aviation Psychology, vol. 14, no. 1, pp. 79-102. doi:10.1207/s15327108ijap1401_5. https://doi.org/10.1207/s15327108ijap1401_5. Retrieved 2026-10-06.
- ↑ Amy L. Alexander, Christopher D. Wickens, Thomas J. Hardy (2005-12). "Synthetic Vision Systems: The Effects of Guidance Symbology, Display Size, and Field of View". Human Factors, vol. 47, no. 4, pp. 693-707. doi:10.1518/001872005775571005. https://doi.org/10.1518/001872005775571005. Retrieved 2026-10-06.