Synthetic Vision Technology, the Digital Terrain Database That Renders the World Inside Your Panel, and the Safety Case the CFIT Numbers Make

Controlled flight into terrain (CFIT) kills crews in airworthy aircraft flown by trained pilots. The solution required more than better technique - it required a database, satellite positioning, and a complete rethinking of what a cockpit display could show. Synthetic Vision Technology (SVT) is the result of that rethinking, and it is still evolving.

The Scale of the CFIT Problem

Through the 1980s and into the 1990s, CFIT accounted for a significant fraction of all fatal commercial aviation accidents globally. Aircraft were airworthy. Crews were current. Flights ended on hillsides because crews lacked an accurate three-dimensional picture of terrain relative to their position.

American Airlines Flight 965 became the defining case. On December 20, 1995, the crew flew a night approach into Cali, Colombia, and selected the wrong waypoint in the flight management system, placing the aircraft on a track toward mountainous terrain. The Ground Proximity Warning System (GPWS) did trigger - but with fewer than 20 seconds of reaction time. 159 of the 163 people on board were killed. That accident became the central argument for the next generation of terrain technology.

Why GPWS Wasn’t Enough

GPWS had been required on large commercial aircraft since 1975. The concept was reactive: measure rate of descent relative to the radio altimeter, check flap and gear configuration, and trigger an audio warning if terrain impact appeared imminent.

It worked. CFIT fatalities in commercial aviation fell after the mandate. But the fundamental limitation was structural - GPWS could sense the terrain directly below. It could not see the mountain ahead. The engineering community called this the look-ahead problem.

How EGPWS and TAWS Solved Look-Ahead

Engineers at AlliedSignal (later acquired by Honeywell) developed the solution through the early 1990s. Their approach combined two data streams:

A Digital Terrain Elevation Database (DTED) covering the entire globe
GPS positioning that placed the aircraft precisely in three-dimensional space

By projecting the aircraft’s flight path forward against the terrain database, the system could answer a question GPWS never could: does my projected path intersect terrain in the next 30 to 60 seconds?

The result was the Enhanced Ground Proximity Warning System (EGPWS). The FAA uses the broader term Terrain Awareness and Warning System (TAWS) for this equipment class. The FAA mandated TAWS on turbine-powered commercial aircraft in the year 2000. Boeing’s annual statistical summaries document what followed: the CFIT accident category TAWS was designed to eliminate essentially collapsed in commercial operations after the mandate took effect.

The Terrain Database Behind the Picture

The underlying data is Digital Terrain Elevation Data (DTED), sourced from organizations including the U.S. Geological Survey and the National Geospatial-Intelligence Agency. It exists at multiple resolutions:

~1 kilometer between data points at coarse resolution
~100 meters at medium resolution
~30 meters in areas with detailed survey coverage

Aviation terrain databases are built from this source material and updated on the standard 28-day aviation update cycle - the same cycle governing navigation charts and approach procedures.

From Warning to Picture: What Synthetic Vision Changed

TAWS was a genuine safety advance, but it remained an alert system. It told you terrain existed and was a threat. It did not show you the shape of the valley, the extent of the ridge, or which direction offered the most escape room. The three-dimensional mental picture of terrain around the aircraft was still something pilots had to construct from charts, briefings, and instrument cross-checks.

Garmin’s engineers, developing what became the G1000 integrated avionics suite in the early 2000s, reframed the question. They already had the terrain database. They already had GPS position. They had continuous attitude data from the Attitude and Heading Reference System (AHRS). The question became: why trigger an alarm when you can build a picture?

Synthetic Vision Technology (SVT) renders the terrain elevation database in real time as a three-dimensional perspective view on the Primary Flight Display (PFD). Instead of a featureless artificial horizon, the pilot sees rendered terrain: rolling hills in the foreground, mountain ridges in the distance, valleys falling away below the flight path. Critically, the display also renders synthetic runway depictions - perspective drawings of the actual destination runway, positioned exactly where it would appear from the aircraft’s current position.

The G1000 received certification in various aircraft in the mid-2000s, including the Cessna 172 Skyhawk and the Beechcraft Bonanza.

How the Rendering Actually Works

The avionics computer combines several data streams continuously:

GPS position (accurate to within a few meters)
Barometric and GPS altitude
Heading, pitch, and roll from the AHRS

Given that position and attitude data, the system queries the terrain database for elevation data in the surrounding area and renders it in a continuous perspective projection. When the aircraft banks left, the terrain picture shifts. When it pitches up, the horizon perspective changes. The mountain ahead fills more of the display as the aircraft closes distance. The synthetic runway grows and resolves as the aircraft descends toward it.

Modern suites - including the G3000 and G5000, found in business turboprops and light jets - extend the picture further with obstacle databases, depicting towers and structures above certain height thresholds. Universal Avionics and Honeywell have developed their own implementations for transport and business aircraft categories.

The Limitations Every SVT Pilot Must Understand

Database coverage is not uniform. In the continental United States and Western Europe, terrain data is detailed and current. In remote areas of Central Asia, sub-Saharan Africa, and parts of South America, resolution drops substantially - data points may be spaced more than a kilometer apart. A ridge 600 meters wide might not appear in the database at that resolution. The display renders normally whether the underlying data is detailed or sparse. The confidence the picture creates does not automatically match the confidence the data supports.

Man-made obstacles are an incomplete category. The obstacle database includes FAA-registered towers and structures above certain height thresholds. It does not include every power line, every guy wire, or any structure added after the last database update. Wire strikes and obstacle collisions remain hazards at the low altitudes where general aviation pilots spend most of their time.

Database currency is an active management responsibility. An SVT display renders identically whether the subscription is current or lapsed months ago. Pilots flying with expired databases face a complacency trap that the system itself cannot flag.

The deeper issue is automation complacency. Synthetic vision is a model of the real world - a very good one, but a model. The safety community has documented a consistent pattern: when a system appears to be monitoring something on a pilot’s behalf, the pilot tends to monitor it less actively. TAWS had this effect in its early adoption years. SVT has it too. The technology does not fail; the human relationship to it shifts, and that shift can erode the safety margin the technology was designed to create.

Where Synthetic Vision Is Headed: Infrastructure-Independent Approaches

The rendering problem for well-covered geographic regions is effectively solved. The frontier now is coupling the synthetic picture to flight guidance.

Garmin and others are developing SVT-enhanced visual operations and synthetic vision approaches. The concept uses the synthetic runway depiction not just as a situational awareness reference but as a stabilization aid during the visual segment of an instrument approach. As the pilot breaks out of clouds, the synthetic runway on the PFD converges with the actual runway visible through the windscreen, providing a continuous reference through the transition.

The further application - in various stages of development and regulatory discussion - would use GPS position accuracy combined with terrain database precision to support lower approach minima at airports without ILS or any ground-based precision guidance equipment. If an aircraft knows its position to within a meter or two, knows the exact three-dimensional location of the runway threshold, and can render both in a stable synthetic picture that the flight director or autopilot can reference, the core building blocks of a precision approach exist without any ground infrastructure.

The implications for general aviation are significant. Thousands of U.S. airports - and far more globally - have no precision approach equipment. Pilots flying into those airports in marginal conditions either accept higher non-precision minima or cancel. If synthetic vision-based approach guidance can be certified to precision approach standards, it brings lower minima to every GPS-equipped aircraft landing at any airport with a solid position fix and a current database. That is an infrastructure-independent path to improved access that general aviation does not currently have.

The certification work is ongoing. The FAA must be satisfied that GPS integrity, terrain database completeness, and obstacle coverage can combine to produce the same safety case as a physical glide slope transmitter. Advisory circulars are being written. Data integrity requirements are being established. The timeline is measured in years, but the direction is clear.

Why This Matters for Pilots Today

For any pilot flying glass cockpit aircraft with SVT, the operational summary is straightforward: use the picture, understand its resolution, keep databases current, and do not let the display substitute for looking outside. The system shows you a model of the world. The world is authoritative.

The technology traveled from a reactive alarm that told you a mountain existed, to a picture that showed you the mountain existed, and it is heading toward guidance that helps you navigate to the runway even when you cannot see it. That is a meaningful arc in aviation safety - and it is not finished.

Key Takeaways

CFIT - controlled flight into terrain - drove the development of terrain awareness technology after accidents like American Airlines Flight 965 (December 1995), which killed 159 of 163 people on board when GPWS could not provide adequate warning time
TAWS, mandated by the FAA in 2000, added look-ahead capability by combining GPS position with a digital terrain elevation database - and effectively eliminated CFIT as a major category in commercial aviation
Synthetic Vision Technology renders that same terrain database as a live, three-dimensional perspective view on the PFD, giving pilots a visual picture of terrain rather than an audio alarm
Key limitations include variable database resolution by region, incomplete obstacle data, and the complacency risk of treating a model as equivalent to direct observation
The next frontier is using SVT coupled with GPS precision to support lower approach minima at airports with no ground-based precision guidance - a potential infrastructure-independent upgrade for thousands of GA airports