Avionics News June 2017 - 18

SEEING THE (INVISIBLE) LIGHT
Continued from page 17

displays - and at costs that put a form of this tool within
reach of ever more aviators.
SVS: An almost all-seeing eye
The synthetic vision system portrays terrain and
known obstacles rendered on a display through the
computer magic of fast digital processing running on
a mass of inexpensive computer memory to replay,
correctly oriented, detailed images of landscape and
other objects. The SVS image derives from details
gathered in earth scans amassed throughout years of
various satellite passes employing varying technologies.
As satellite-scan resolution capabilities increased, the
depth of the data deepened, yielding ever larger numbers
of smaller grid points, both laterally and vertically.
GPS position information provides the reference
point for the Earth view; track and velocity inform the
perspectives of the image's angle of view and speed
across the display.
The results become conformal images of the landscape
- ahead, left, right, behind and below the aircraft.
The view is dynamic - that is, processors render these
images as fluid, moving views passing beneath the
aircraft at a rate proportional to its ground speed. The
landscape images appear in full, lush colors, neither the
wire-frame graphics of years past nor the monochromatic
real-world-in-infrared images produced by infrared
sensors for display by EVS.
These two truly complementary technologies deliver
more than their individual parts - that is, they are
additive in value when both are available, particularly
when combined on a single screen as available in some
high-end avionics packages.
But even alone, the utility and capabilities of both
continue to expand, with the technologies becoming
more available and more useful to the pilots flying
behind the image. And they both work in-flight and on
the ground.
Pilots must know the limitations:
The complementary capabilities and
limitations of EVS and SVS
As with so many aviation tools, vision-enhancing and
vision-synthesizing tools each suffer some limitations.
Truly complementary tools, each retains its individual
utility - but the key to their safe use grows out of
understanding those limitations. One has limited vision;
the other sees only what it remembers.
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avionics news

june

2017

EVS boasts one trait that makes it a desirable flying
companion: real-world, real-time vision - or as-it-isnow, real-time immediacy. If it shows up on an EVS
display, it's there - or was only moments earlier.
Conversely, SVS doesn't truly see so much as it
shows. And what it shows exists only in its database. If a
fence, wall, building or tree didn't exist at the time of the
landscape scan in use, it won't - can't, actually - show
up in an SVS image.
But SVS is immune to all forms of atmospheric
contamination known to thwart the view of an EVS
sensor because it isn't "seeing" the world through a
sensor. It's simply replaying the world from computer
memory. Think of all those Level D flight simulators
"flying" in buildings at flight-training companies.
A deer on the runway should show on an EVS display,
even in pitch-dark conditions - but SVS can't "see" a
deer that wasn't there during the last scan. This leaves
Bambi invisible to an SVS user.
But in conditions that neutralize the ability of an EVS
sensor to see beyond its lens, SVS continues to display
its view of the world as stored in its database.
It's that "permanent VFR view" that drives the
popularity growth of SVS - also with its widespread
availability and relative affordability. Options available
for both EVS and SVS are numerous.
EVS options
Gulfstream Aerospace recognized early on the value of
EVS, earning the first approval for civil aircraft in 2001
when the Federal Aviation Administration approved the
technology for use in the then-top-line Gulfstream V. In
the years since, the technology has moved up and down
the general aviation fleets.
AEA member Astronics AES offers arguably the
widest range of EVS products for general aviation, a line
called Max-Viz.
Astronics Max-Viz EVS packages are available for
turbine and piston, fixed- and rotary-wing aircraft. The
systems' infrared sensors, sensor-signal processing,
and advanced cockpit display show terrain, runways,
taxiways, aircraft and obstacles in poor visibility
conditions - even in light fog, haze, smoke, smog, light
precipitation and darkness.
Max-Viz EVS became an early option in the SR line
of single-engine piston aircraft, and Cirrus Aircraft
continues to offer the equipment in its latest generation
SR20 and SR22 equipped with the Garmin Perspective
by Cirrus version of the G1000 NXi panel.
Astronics Max-Viz EVS systems also are in use
on aircraft from AgustaWestland, Textron Aviation

Table of Contents for the Digital Edition of Avionics News June 2017