<s>
An	O
external	B-Application
vision	I-Application
system	I-Application
(	O
XVS	O
)	O
refers	O
to	O
any	O
of	O
several	O
methods	O
to	O
provide	O
the	O
pilot	O
of	O
an	O
aircraft	O
with	O
a	O
means	O
to	O
see	O
outside	O
the	O
aircraft	O
where	O
traditional	O
windscreens	O
may	O
not	O
be	O
feasible	O
due	O
to	O
the	O
aircraft	O
configuration	O
.	O
</s>
<s>
An	O
XVS	O
would	O
consist	O
of	O
external	O
sensors	B-Application
,	O
primarily	O
video	O
imagery	O
,	O
which	O
is	O
provided	O
to	O
the	O
pilot(s )	O
in	O
real	B-General_Concept
time	O
via	O
one	O
or	O
more	O
displays	O
intended	O
to	O
augment	O
or	O
replace	O
the	O
windscreen	O
.	O
</s>
<s>
Both	O
enhanced	B-Device
vision	I-Device
systems	I-Device
(	O
EVS	O
)	O
and	O
synthetic	B-General_Concept
vision	I-General_Concept
system	I-General_Concept
(	O
SVS	O
)	O
have	O
become	O
standard	O
equipment	O
on	O
many	O
larger	O
business	O
jets	O
such	O
as	O
those	O
manufactured	O
by	O
Gulfstream	O
,	O
Bombardier	O
,	O
Dassault	O
,	O
and	O
most	O
recently	O
,	O
Embraer	O
.	O
</s>
<s>
However	O
,	O
EVS	O
typically	O
provides	O
the	O
pilot(s )	O
with	O
an	O
infrared	O
video	O
image	O
,	O
usually	O
displayed	O
on	O
the	O
head-up	B-Application
display	I-Application
(	O
HUD	B-Application
)	O
,	O
which	O
overlays	O
the	O
pilot	O
view	O
of	O
the	O
outside	O
world	O
through	O
the	O
windscreen	O
.	O
</s>
<s>
SVS	O
can	O
also	O
be	O
displayed	O
conformally	O
on	O
the	O
HUD	B-Application
,	O
but	O
it	O
is	O
not	O
real	B-General_Concept
time	O
in	O
that	O
anything	O
that	O
is	O
not	O
part	O
of	O
the	O
static	O
terrain	O
database	O
cannot	O
be	O
displayed	O
.	O
</s>
<s>
Both	O
EVS	O
and	O
SVS	O
are	O
primarily	O
intended	O
to	O
improve	O
situational	O
awareness	O
of	O
the	O
flight	O
deck	O
crew	O
,	O
especially	O
at	O
night	O
and	O
in	O
poor	O
visibility	B-Application
weather	O
conditions	O
such	O
as	O
rain	O
,	O
snow	O
,	O
fog	O
,	O
or	O
smoke	O
.	O
</s>
<s>
XVS	O
is	O
different	O
in	O
that	O
it	O
is	O
intended	O
to	O
provide	O
the	O
flight	O
deck	O
crew	O
a	O
real	B-General_Concept
time	O
view	O
of	O
the	O
outside	O
world	O
in	O
visual	O
meteorological	O
conditions	O
(	O
VMC	O
)	O
.	O
</s>
