<s>
Air	B-Application
traffic	I-Application
control	I-Application
(	O
ATC	O
)	O
is	O
a	O
service	O
provided	O
by	O
ground-based	O
air	B-Application
traffic	I-Application
controllers	I-Application
(	O
also	O
called	O
control	O
tower	O
operators	O
(	O
CTO	O
)	O
)	O
who	O
direct	O
aircraft	O
on	O
the	O
ground	O
and	O
through	O
a	O
given	O
section	O
of	O
controlled	O
airspace	O
,	O
and	O
can	O
provide	O
advisory	O
services	O
to	O
aircraft	O
in	O
non-controlled	O
airspace	O
.	O
</s>
<s>
The	O
primary	O
purpose	O
of	O
ATC	O
worldwide	O
is	O
to	O
prevent	O
collisions	O
,	O
organize	O
and	O
expedite	O
the	O
flow	O
of	O
air	B-Application
traffic	I-Application
,	O
and	O
provide	O
information	O
and	O
other	O
support	O
for	O
pilots	O
.	O
</s>
<s>
Air	B-Application
traffic	I-Application
controllers	I-Application
monitor	O
the	O
location	O
of	O
aircraft	O
in	O
their	O
assigned	O
airspace	O
by	O
radar	B-Application
and	O
communicate	O
with	O
the	O
pilots	O
by	O
radio	O
.	O
</s>
<s>
Pursuant	O
to	O
requirements	O
of	O
the	O
International	B-General_Concept
Civil	I-General_Concept
Aviation	I-General_Concept
Organization	I-General_Concept
(	O
ICAO	O
)	O
,	O
ATC	O
operations	O
are	O
conducted	O
either	O
in	O
the	O
English	O
language	O
or	O
the	O
language	O
used	O
by	O
the	O
station	O
on	O
the	O
ground	O
.	O
</s>
<s>
In	O
1920	O
,	O
Croydon	O
Airport	O
,	O
London	O
,	O
was	O
the	O
first	O
airport	O
in	O
the	O
world	O
to	O
introduce	O
air	B-Application
traffic	I-Application
control	I-Application
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
air	B-Application
traffic	I-Application
control	I-Application
developed	O
three	O
divisions	O
.	O
</s>
<s>
The	O
first	O
airport	B-Application
traffic	I-Application
control	I-Application
tower	I-Application
,	O
regulating	O
arrivals	O
,	O
departures	O
and	O
surface	O
movement	O
of	O
aircraft	O
at	O
a	O
specific	O
airport	O
,	O
opened	O
in	O
Cleveland	O
in	O
1930	O
.	O
</s>
<s>
Approach/departure	O
control	O
facilities	O
were	O
created	O
after	O
adoption	O
of	O
radar	B-Application
in	O
the	O
1950s	O
to	O
monitor	O
and	O
control	O
the	O
busy	O
airspace	O
around	O
larger	O
airports	O
.	O
</s>
<s>
Air	B-Application
traffic	I-Application
controllers	I-Application
are	O
responsible	O
for	O
the	O
separation	O
and	O
efficient	O
movement	O
of	O
aircraft	O
and	O
vehicles	O
operating	O
on	O
the	O
taxiways	O
and	O
runways	O
of	O
the	O
airport	O
itself	O
,	O
and	O
aircraft	O
in	O
the	O
air	O
near	O
the	O
airport	O
,	O
generally	O
5	O
to	O
10	O
nautical	O
miles	O
(	O
9	O
to	O
18km	O
)	O
depending	O
on	O
the	O
airport	O
procedures	O
.	O
</s>
<s>
Surveillance	O
displays	O
are	O
also	O
available	O
to	O
controllers	O
at	O
larger	O
airports	O
to	O
assist	O
with	O
controlling	O
air	B-Application
traffic	I-Application
.	O
</s>
<s>
Controllers	O
may	O
use	O
a	O
radar	B-Application
system	I-Application
called	O
secondary	O
surveillance	O
radar	B-Application
for	O
airborne	O
traffic	O
approaching	O
and	O
departing	O
.	O
</s>
<s>
In	O
adverse	O
weather	O
conditions	O
,	O
the	O
tower	O
controllers	O
may	O
also	O
use	O
surface	O
movement	O
radar	B-Application
(	O
SMR	O
)	O
,	O
surface	O
movement	O
guidance	O
and	O
control	O
system	O
(	O
SMGCS	O
)	O
,	O
or	O
advanced	O
surface	O
movement	O
guidance	O
and	O
control	O
system	O
(	O
ASMGCS	O
)	O
to	O
control	O
traffic	O
on	O
the	O
maneuvering	O
area	O
(	O
taxiways	O
and	O
runway	O
)	O
.	O
</s>
<s>
The	O
areas	O
of	O
responsibility	O
for	O
tower	O
controllers	O
fall	O
into	O
three	O
general	O
operational	O
disciplines	O
:	O
local	O
control	O
or	O
air	B-Application
control	I-Application
,	O
ground	O
control	O
,	O
and	O
flight	O
data/clearance	O
delivery	O
—	O
other	O
categories	O
,	O
such	O
as	O
airport	O
apron	O
control	O
or	O
ground	O
movement	O
planner	O
,	O
may	O
exist	O
at	O
extremely	O
busy	O
airports	O
.	O
</s>
<s>
Remote	O
and	O
virtual	O
tower	O
(	O
RVT	O
)	O
is	O
a	O
system	O
based	O
on	O
air	B-Application
traffic	I-Application
controllers	I-Application
being	O
located	O
somewhere	O
other	O
than	O
at	O
the	O
local	O
airport	O
tower	O
and	O
still	O
able	O
to	O
provide	O
air	B-Application
traffic	I-Application
control	I-Application
services	O
.	O
</s>
<s>
Displays	O
for	O
the	O
air	B-Application
traffic	I-Application
controllers	I-Application
may	O
be	O
live	O
video	O
,	O
synthetic	O
images	O
based	O
on	O
surveillance	O
sensor	O
data	O
,	O
or	O
both	O
.	O
</s>
<s>
Some	O
busier	O
airports	O
have	O
surface	O
movement	O
radar	B-Application
(	O
SMR	O
)	O
,	O
such	O
as	O
ASDE-3	O
,	O
AMASS	O
,	O
or	O
ASDE-X	O
,	O
designed	O
to	O
display	O
aircraft	O
and	O
vehicles	O
on	O
the	O
ground	O
.	O
</s>
<s>
Newer	O
systems	O
include	O
the	O
capability	O
to	O
display	O
higher-quality	O
mapping	O
,	O
radar	B-Application
targets	O
,	O
data	O
blocks	O
,	O
and	O
safety	O
alerts	O
,	O
and	O
to	O
interface	O
with	O
other	O
systems	O
such	O
as	O
digital	O
flight	O
strips	O
.	O
</s>
<s>
Air	B-Application
control	I-Application
(	O
known	O
to	O
pilots	O
as	O
or	O
)	O
is	O
responsible	O
for	O
the	O
active	O
runway	O
surfaces	O
.	O
</s>
<s>
Air	B-Application
control	I-Application
clears	O
aircraft	O
for	O
takeoff	O
or	O
landing	O
,	O
ensuring	O
that	O
prescribed	O
runway	O
separation	O
will	O
exist	O
at	O
all	O
times	O
.	O
</s>
<s>
Within	O
the	O
tower	O
,	O
a	O
highly	O
disciplined	O
communications	O
process	O
between	O
the	O
air	B-Application
control	I-Application
and	O
ground	O
control	O
is	O
an	O
absolute	O
necessity	O
.	O
</s>
<s>
Air	B-Application
control	I-Application
must	O
ensure	O
that	O
ground	O
control	O
is	O
aware	O
of	O
any	O
operations	O
that	O
will	O
impact	O
the	O
taxiways	O
,	O
and	O
work	O
with	O
the	O
approach	O
radar	B-Application
controllers	O
to	O
create	O
in	O
the	O
arrival	O
traffic	O
to	O
allow	O
taxiing	O
traffic	O
to	O
cross	O
runways	O
and	O
to	O
allow	O
departing	O
aircraft	O
to	O
take	O
off	O
.	O
</s>
<s>
Crew	B-Error_Name
resource	I-Error_Name
management	I-Error_Name
(	O
CRM	O
)	O
procedures	O
are	O
often	O
used	O
to	O
ensure	O
this	O
communication	O
process	O
is	O
efficient	O
and	O
clear	O
.	O
</s>
<s>
Clearance	O
delivery	O
or	O
,	O
at	O
busy	O
airports	O
,	O
(	O
GMP	O
)	O
or	O
(	O
TMC	O
)	O
will	O
,	O
if	O
necessary	O
,	O
coordinate	O
with	O
the	O
relevant	O
radar	B-Application
center	O
or	O
flow	O
control	O
unit	O
to	O
obtain	O
releases	O
for	O
aircraft	O
.	O
</s>
<s>
This	O
information	O
is	O
also	O
coordinated	O
with	O
the	O
relevant	O
radar	B-Application
center	O
or	O
flow	O
control	O
unit	O
and	O
ground	O
control	O
to	O
ensure	O
that	O
the	O
aircraft	O
reaches	O
the	O
runway	O
in	O
time	O
to	O
meet	O
the	O
time	O
restriction	O
provided	O
by	O
the	O
relevant	O
unit	O
.	O
</s>
<s>
Many	O
airports	O
have	O
a	O
radar	B-Application
control	O
facility	O
that	O
is	O
associated	O
with	O
the	O
airport	O
.	O
</s>
<s>
In	O
most	O
countries	O
,	O
this	O
is	O
referred	O
to	O
as	O
terminal	O
control	O
and	O
abbreviated	O
to	O
TMC	O
;	O
in	O
the	O
U.S.	O
,	O
it	O
is	O
referred	O
to	O
as	O
a	O
TRACON	O
(	O
terminal	B-Application
radar	I-Application
approach	I-Application
control	I-Application
)	O
.	O
</s>
<s>
Not	O
all	O
airports	O
have	O
a	O
radar	B-Application
approach	O
or	O
terminal	O
control	O
available	O
.	O
</s>
<s>
At	O
some	O
of	O
these	O
airports	O
,	O
the	O
tower	O
may	O
provide	O
a	O
non-radar	O
procedural	O
approach	O
service	O
to	O
arriving	O
aircraft	O
handed	O
over	O
from	O
a	O
radar	B-Application
unit	O
before	O
they	O
are	O
visual	O
to	O
land	O
.	O
</s>
<s>
Some	O
units	O
also	O
have	O
a	O
dedicated	O
approach	O
unit	O
which	O
can	O
provide	O
the	O
procedural	O
approach	O
service	O
either	O
all	O
the	O
time	O
or	O
for	O
any	O
periods	O
of	O
radar	B-Application
outage	O
for	O
any	O
reason	O
.	O
</s>
<s>
Air	B-Application
traffic	I-Application
controllers	I-Application
have	O
different	O
responsibilities	O
to	O
aircraft	O
operating	O
under	O
the	O
different	O
sets	O
of	O
rules	O
.	O
</s>
<s>
En-route	O
air	B-Application
traffic	I-Application
controllers	I-Application
issue	O
clearances	O
and	O
instructions	O
for	O
airborne	O
aircraft	O
,	O
and	O
pilots	O
are	O
required	O
to	O
comply	O
with	O
these	O
instructions	O
.	O
</s>
<s>
En-route	O
controllers	O
also	O
provide	O
air	B-Application
traffic	I-Application
control	I-Application
services	O
to	O
many	O
smaller	O
airports	O
around	O
the	O
country	O
,	O
including	O
clearance	O
off	O
of	O
the	O
ground	O
and	O
clearance	O
for	O
approach	O
to	O
an	O
airport	O
.	O
</s>
<s>
En-route	O
air	B-Application
traffic	I-Application
controllers	I-Application
work	O
in	O
facilities	O
called	O
air	B-Application
traffic	I-Application
control	I-Application
centers	O
,	O
each	O
of	O
which	O
is	O
commonly	O
referred	O
to	O
as	O
a	O
"	O
center	O
"	O
.	O
</s>
<s>
In	O
some	O
cases	O
this	O
"	O
hand-off	O
"	O
process	O
involves	O
a	O
transfer	O
of	O
identification	O
and	O
details	O
between	O
controllers	O
so	O
that	O
air	B-Application
traffic	I-Application
control	I-Application
services	O
can	O
be	O
provided	O
in	O
a	O
seamless	O
manner	O
;	O
in	O
other	O
cases	O
local	O
agreements	O
may	O
allow	O
"	O
silent	O
handovers	O
"	O
such	O
that	O
the	O
receiving	O
center	O
does	O
not	O
require	O
any	O
co-ordination	O
if	O
traffic	O
is	O
presented	O
in	O
an	O
agreed	O
manner	O
.	O
</s>
<s>
Since	O
centers	O
control	O
a	O
large	O
airspace	O
area	O
,	O
they	O
will	O
typically	O
use	O
long	O
range	O
radar	B-Application
that	O
has	O
the	O
capability	O
,	O
at	O
higher	O
altitudes	O
,	O
to	O
see	O
aircraft	O
within	O
of	O
the	O
radar	B-Application
antenna	O
.	O
</s>
<s>
They	O
may	O
also	O
use	O
radar	B-Application
data	O
to	O
control	O
when	O
it	O
provides	O
a	O
better	O
"	O
picture	O
"	O
of	O
the	O
traffic	O
or	O
when	O
it	O
can	O
fill	O
in	O
a	O
portion	O
of	O
the	O
area	O
not	O
covered	O
by	O
the	O
long	O
range	O
radar	B-Application
.	O
</s>
<s>
In	O
the	O
U.S.	O
system	O
,	O
at	O
higher	O
altitudes	O
,	O
over	O
90%	O
of	O
the	O
U.S.	O
airspace	O
is	O
covered	O
by	O
radar	B-Application
and	O
often	O
by	O
multiple	O
radar	B-Application
systems	I-Application
;	O
however	O
,	O
coverage	O
may	O
be	O
inconsistent	O
at	O
lower	O
altitudes	O
used	O
by	O
aircraft	O
due	O
to	O
high	O
terrain	O
or	O
distance	O
from	O
radar	B-Application
facilities	O
.	O
</s>
<s>
A	O
center	O
may	O
require	O
numerous	O
radar	B-Application
systems	I-Application
to	O
cover	O
the	O
airspace	O
assigned	O
to	O
them	O
,	O
and	O
may	O
also	O
rely	O
on	O
pilot	O
position	O
reports	O
from	O
aircraft	O
flying	O
below	O
the	O
floor	O
of	O
radar	B-Application
coverage	O
.	O
</s>
<s>
To	O
address	O
this	O
,	O
automation	O
systems	O
have	O
been	O
designed	O
that	O
consolidate	O
the	O
radar	B-Application
data	O
for	O
the	O
controller	O
.	O
</s>
<s>
This	O
consolidation	O
includes	O
eliminating	O
duplicate	O
radar	B-Application
returns	O
,	O
ensuring	O
the	O
best	O
radar	B-Application
for	O
each	O
geographical	O
area	O
is	O
providing	O
the	O
data	O
,	O
and	O
displaying	O
the	O
data	O
in	O
an	O
effective	O
format	O
.	O
</s>
<s>
Because	O
there	O
are	O
no	O
radar	B-Application
systems	I-Application
available	O
for	O
oceanic	O
control	O
,	O
oceanic	O
controllers	O
provide	O
ATC	O
services	O
using	O
procedural	O
control	O
.	O
</s>
<s>
have	O
implemented	O
automatic	B-Application
dependent	I-Application
surveillance	I-Application
–	I-Application
broadcast	I-Application
(	O
ADS-B	B-Application
)	O
as	O
part	O
of	O
their	O
surveillance	O
capability	O
.	O
</s>
<s>
This	O
new	O
technology	O
reverses	O
the	O
radar	B-Application
concept	O
.	O
</s>
<s>
Instead	O
of	O
radar	B-Application
"	O
finding	O
"	O
a	O
target	O
by	O
interrogating	O
the	O
transponder	B-Architecture
,	O
the	O
ADS-B	B-Application
equipped	O
aircraft	O
sends	O
a	O
position	O
report	O
as	O
determined	O
by	O
the	O
navigation	O
equipment	O
on	O
board	O
the	O
aircraft	O
.	O
</s>
<s>
ADS-C	O
is	O
another	O
mode	O
of	O
automatic	B-Application
dependent	I-Application
surveillance	I-Application
,	O
however	O
ADS-C	O
operates	O
in	O
the	O
"	O
contract	O
"	O
mode	O
where	O
the	O
aircraft	O
reports	O
a	O
position	O
,	O
automatically	O
or	O
initiated	O
by	O
the	O
pilot	O
,	O
based	O
on	O
a	O
predetermined	O
time	O
interval	O
.	O
</s>
<s>
ADS-C	O
is	O
significant	O
because	O
it	O
can	O
be	O
used	O
where	O
it	O
is	O
not	O
possible	O
to	O
locate	O
the	O
infrastructure	O
for	O
a	O
radar	B-Application
system	I-Application
(	O
e.g.	O
,	O
over	O
water	O
)	O
.	O
</s>
<s>
Computerized	O
radar	B-Application
displays	O
are	O
now	O
being	O
designed	O
to	O
accept	O
ADS-C	O
inputs	O
as	O
part	O
of	O
the	O
display	O
.	O
</s>
<s>
Precision	O
approach	O
radars	B-Application
(	O
PAR	O
)	O
are	O
commonly	O
used	O
by	O
military	O
controllers	O
of	O
air	O
forces	O
of	O
several	O
countries	O
,	O
to	O
assist	O
the	O
pilot	O
in	O
final	O
phases	O
of	O
landing	O
in	O
places	O
where	O
instrument	O
landing	O
system	O
and	O
other	O
sophisticated	O
airborne	O
equipment	O
are	O
unavailable	O
to	O
assist	O
the	O
pilots	O
in	O
marginal	O
or	O
near	O
zero	O
visibility	O
conditions	O
.	O
</s>
<s>
A	O
radar	B-Application
archive	O
system	O
(	O
RAS	O
)	O
keeps	O
an	O
electronic	O
record	O
of	O
all	O
radar	B-Application
information	O
,	O
preserving	O
it	O
for	O
a	O
few	O
weeks	O
.	O
</s>
<s>
When	O
an	O
aircraft	O
has	O
'	O
disappeared	O
 '	O
from	O
radar	B-Application
screens	O
,	O
a	O
controller	O
can	O
review	O
the	O
last	O
radar	B-Application
returns	O
from	O
the	O
aircraft	O
to	O
determine	O
its	O
likely	O
position	O
.	O
</s>
<s>
RAS	O
is	O
also	O
useful	O
to	O
technicians	O
who	O
are	O
maintaining	O
radar	B-Application
systems	I-Application
.	O
</s>
<s>
The	O
mapping	O
of	O
flights	O
in	O
real-time	O
is	O
based	O
on	O
the	O
air	B-Application
traffic	I-Application
control	I-Application
system	I-Application
,	O
and	O
volunteer	O
ADS-B	B-Application
receivers	O
.	O
</s>
<s>
Subsequently	O
,	O
NBAA	O
advocated	O
the	O
broad-scale	O
dissemination	O
of	O
air	B-Application
traffic	I-Application
data	O
.	O
</s>
<s>
Stand-alone	O
programs	O
are	O
also	O
available	O
for	O
displaying	O
the	O
geographic	O
location	O
of	O
airborne	O
IFR	O
(	O
instrument	O
flight	O
rules	O
)	O
air	B-Application
traffic	I-Application
anywhere	O
in	O
the	O
FAA	O
air	B-Application
traffic	I-Application
system	O
.	O
</s>
<s>
The	O
programs	O
can	O
overlay	O
air	B-Application
traffic	I-Application
with	O
a	O
wide	O
selection	O
of	O
maps	O
such	O
as	O
,	O
geo-political	O
boundaries	O
,	O
air	B-Application
traffic	I-Application
control	I-Application
center	O
boundaries	O
,	O
high	O
altitude	O
jet	O
routes	O
,	O
satellite	O
cloud	O
and	O
radar	B-Application
imagery	O
.	O
</s>
<s>
The	O
day-to-day	O
problems	O
faced	O
by	O
the	O
air	B-Application
traffic	I-Application
control	I-Application
system	I-Application
are	O
primarily	O
related	O
to	O
the	O
volume	O
of	O
air	B-Application
traffic	I-Application
demand	O
placed	O
on	O
the	O
system	O
and	O
weather	O
.	O
</s>
<s>
Air	B-Application
traffic	I-Application
control	I-Application
errors	O
occur	O
when	O
the	O
separation	O
(	O
either	O
vertical	O
or	O
horizontal	O
)	O
between	O
airborne	O
aircraft	O
falls	O
below	O
the	O
minimum	O
prescribed	O
separation	O
set	O
(	O
for	O
the	O
domestic	O
United	O
States	O
)	O
by	O
the	O
US	O
Federal	O
Aviation	O
Administration	O
.	O
</s>
<s>
However	O
,	O
at	O
some	O
ACCs	O
,	O
air	B-Application
traffic	I-Application
controllers	I-Application
still	O
record	O
data	O
for	O
each	O
flight	O
on	O
strips	O
of	O
paper	O
and	O
personally	O
coordinate	O
their	O
paths	O
.	O
</s>
<s>
A	O
prerequisite	O
to	O
safe	O
air	B-Application
traffic	I-Application
separation	O
is	O
the	O
assignment	O
and	O
use	O
of	O
distinctive	O
call	O
signs	O
.	O
</s>
<s>
As	O
such	O
they	O
appear	O
on	O
flight	O
plans	O
and	O
ATC	O
radar	B-Application
labels	O
.	O
</s>
<s>
There	O
are	O
also	O
the	O
audio	O
or	O
Radiotelephony	O
callsigns	O
used	O
on	O
the	O
radio	O
contact	O
between	O
pilots	O
and	O
air	B-Application
traffic	I-Application
control	I-Application
.	O
</s>
<s>
The	O
IATA	O
callsigns	O
are	O
currently	O
used	O
in	O
aerodromes	O
on	O
the	O
announcement	O
tables	O
but	O
are	O
no	O
longer	O
used	O
in	O
air	B-Application
traffic	I-Application
control	I-Application
.	O
</s>
<s>
Additionally	O
,	O
it	O
is	O
the	O
right	O
of	O
the	O
air	B-Application
traffic	I-Application
controller	I-Application
to	O
change	O
the	O
'	O
audio	O
 '	O
callsign	O
for	O
the	O
period	O
the	O
flight	O
is	O
in	O
his	O
sector	O
if	O
there	O
is	O
a	O
risk	O
of	O
confusion	O
,	O
usually	O
choosing	O
the	O
tail	O
number	O
instead	O
.	O
</s>
<s>
Many	O
technologies	O
are	O
used	O
in	O
air	B-Application
traffic	I-Application
control	I-Application
systems	I-Application
.	O
</s>
<s>
Primary	O
and	O
secondary	O
radar	B-Application
are	O
used	O
to	O
enhance	O
a	O
controller	O
's	O
situation	O
awareness	O
within	O
his	O
assigned	O
airspace	O
–	O
all	O
types	O
of	O
aircraft	O
send	O
back	O
primary	O
echoes	O
of	O
varying	O
sizes	O
to	O
controllers	O
 '	O
screens	O
as	O
radar	B-Application
energy	O
is	O
bounced	O
off	O
their	O
skins	O
,	O
and	O
transponder-equipped	O
aircraft	O
reply	O
to	O
secondary	O
radar	B-Application
interrogations	O
by	O
giving	O
an	O
ID	O
(	O
Mode	O
A	O
)	O
,	O
an	O
altitude	O
(	O
Mode	B-Architecture
C	I-Architecture
)	O
and/or	O
a	O
unique	O
callsign	O
(	O
Mode	O
S	O
)	O
.	O
</s>
<s>
Certain	O
types	O
of	O
weather	O
may	O
also	O
register	O
on	O
the	O
radar	B-Application
screen	O
.	O
</s>
<s>
These	O
inputs	O
,	O
added	O
to	O
data	O
from	O
other	O
radars	B-Application
,	O
are	O
correlated	O
to	O
build	O
the	O
air	O
situation	O
.	O
</s>
<s>
Some	O
basic	O
processing	O
occurs	O
on	O
the	O
radar	B-Application
tracks	O
,	O
such	O
as	O
calculating	O
ground	O
speed	O
and	O
magnetic	O
headings	O
.	O
</s>
<s>
All	O
this	O
information	O
is	O
distributed	O
to	O
modern	O
operational	B-Device
display	I-Device
systems	I-Device
,	O
making	O
it	O
available	O
to	O
controllers	O
.	O
</s>
<s>
MTCD	O
)	O
,	O
and	O
distributes	O
such	O
processed	O
information	O
to	O
all	O
the	O
stakeholders	O
(	O
air	B-Application
traffic	I-Application
controllers	I-Application
,	O
collateral	O
centers	O
,	O
airports	O
,	O
etc	O
.	O
</s>
<s>
the	O
airline	O
,	O
ground	O
handling	O
and	O
air	B-Application
traffic	I-Application
control	I-Application
(	O
ATC	O
)	O
)	O
.	O
</s>
<s>
Mode	O
S	O
:	O
provides	O
a	O
data	O
downlink	O
of	O
flight	O
parameters	O
via	O
secondary	O
surveillance	O
radars	B-Application
allowing	O
radar	B-Application
processing	O
systems	O
and	O
therefore	O
controllers	O
to	O
see	O
various	O
data	O
on	O
a	O
flight	O
,	O
including	O
airframe	O
unique	O
id	O
(	O
24-bits	O
encoded	O
)	O
,	O
indicated	O
airspeed	O
and	O
flight	O
director	O
selected	O
level	O
,	O
amongst	O
others	O
.	O
</s>
<s>
CPDLC	B-Device
:	O
controller-pilot	B-Device
data	I-Device
link	I-Device
communications	I-Device
–	O
allows	O
digital	O
messages	O
to	O
be	O
sent	O
between	O
controllers	O
and	O
pilots	O
,	O
avoiding	O
the	O
need	O
to	O
use	O
radiotelephony	O
.	O
</s>
<s>
It	O
is	O
especially	O
useful	O
in	O
areas	O
where	O
difficult-to-use	O
HF	B-Algorithm
radiotelephony	O
was	O
previously	O
used	O
for	O
communication	O
with	O
aircraft	O
,	O
e.g.	O
</s>
<s>
ADS-B	B-Application
:	O
automatic	B-Application
dependent	I-Application
surveillance	I-Application
broadcast	I-Application
–	O
provides	O
a	O
data	O
downlink	O
of	O
various	O
flight	O
parameters	O
to	O
air	B-Application
traffic	I-Application
control	I-Application
systems	I-Application
via	O
the	O
transponder	B-Architecture
(	O
1090MHz	O
)	O
and	O
reception	O
of	O
those	O
data	O
by	O
other	O
aircraft	O
in	O
the	O
vicinity	O
.	O
</s>
<s>
The	O
most	O
important	O
is	O
the	O
aircraft	O
's	O
latitude	O
,	O
longitude	O
and	O
level	O
:	O
such	O
data	O
can	O
be	O
utilized	O
to	O
create	O
a	O
radar-like	O
display	O
of	O
aircraft	O
for	O
controllers	O
and	O
thus	O
allows	O
a	O
form	O
of	O
pseudo-radar	O
control	O
to	O
be	O
done	O
in	O
areas	O
where	O
the	O
installation	O
of	O
radar	B-Application
is	O
either	O
prohibitive	O
on	O
the	O
grounds	O
of	O
low	O
traffic	O
levels	O
,	O
or	O
technically	O
not	O
feasible	O
(	O
e.g.	O
</s>
<s>
The	O
electronic	O
flight	O
strip	O
system	O
(	O
e-strip	B-Application
)	O
:	O
</s>
<s>
E-strips	B-Application
allows	O
controllers	O
to	O
manage	O
electronic	O
flight	O
data	O
online	O
without	O
paper	O
strips	O
,	O
reducing	O
the	O
need	O
for	O
manual	O
functions	O
,	O
creating	O
new	O
tools	O
and	O
reducing	O
the	O
ATCO	O
's	O
workload	O
.	O
</s>
<s>
DECEA	O
in	O
Brazil	O
is	O
the	O
world	O
's	O
largest	O
user	O
of	O
tower	O
e-strips	B-Application
system	O
,	O
ranging	O
from	O
very	O
small	O
airports	O
up	O
to	O
the	O
busiest	O
ones	O
,	O
taking	O
the	O
advantage	O
of	O
real	O
time	O
information	O
and	O
data	O
collection	O
from	O
each	O
of	O
more	O
than	O
150	O
sites	O
for	O
use	O
in	O
air	B-Application
traffic	I-Application
flow	O
management	O
(	O
ATFM	O
)	O
,	O
billing	O
and	O
statistics	O
.	O
</s>
<s>
Communication	O
navigation	O
surveillance	O
/	O
air	B-Application
traffic	I-Application
management	O
(	O
CNS/ATM	O
)	O
systems	O
are	O
communications	O
,	O
navigation	O
,	O
and	O
surveillance	O
systems	O
,	O
employing	O
digital	O
technologies	O
,	O
including	O
satellite	O
systems	O
together	O
with	O
various	O
levels	O
of	O
automation	O
,	O
applied	O
in	O
support	O
of	O
a	O
seamless	O
global	O
air	B-Application
traffic	I-Application
management	O
system	O
.	O
</s>
<s>
Free	O
flight	O
is	O
a	O
developing	O
air	B-Application
traffic	I-Application
control	I-Application
method	O
that	O
uses	O
no	O
centralized	O
control	O
(	O
e.g.	O
</s>
<s>
air	B-Application
traffic	I-Application
controllers	I-Application
)	O
.	O
</s>
<s>
In	O
Europe	O
,	O
the	O
SESAR	O
(	O
Single	O
European	O
Sky	O
ATM	O
Research	O
)	O
programme	O
plans	O
to	O
develop	O
new	O
methods	O
,	O
technologies	O
,	O
procedures	O
,	O
and	O
systems	O
to	O
accommodate	O
future	O
(	O
2020	O
and	O
beyond	O
)	O
air	B-Application
traffic	I-Application
needs	O
.	O
</s>
<s>
Single	O
air-traffic	B-Application
control	I-Application
services	O
in	O
continent-sized	O
America	O
and	O
China	O
does	O
not	O
alleviate	O
congestion	O
.	O
</s>
<s>
Air	B-Application
traffic	I-Application
control	I-Application
privatization	O
has	O
been	O
successful	O
in	O
Canada	O
with	O
the	O
creation	O
of	O
Nav	O
Canada	O
,	O
a	O
private	O
nonprofit	O
organization	O
which	O
has	O
reduced	O
costs	O
and	O
has	O
allowed	O
new	O
technologies	O
to	O
be	O
deployed	O
faster	O
due	O
to	O
the	O
elimination	O
of	O
much	O
of	O
the	O
bureaucratic	O
red	O
tape	O
.	O
</s>
<s>
Also	O
within	O
each	O
zone	O
are	O
portions	O
of	O
airspace	O
,	O
about	O
50	O
miles	O
(	O
80.5	O
km	O
)	O
in	O
diameter	O
,	O
called	O
TRACON	O
(	O
Terminal	B-Application
Radar	I-Application
Approach	I-Application
Control	I-Application
)	O
airspaces	O
.	O
</s>
<s>
FAA	O
control	O
tower	O
operators	O
(	O
CTO	O
)	O
/	O
air	B-Application
traffic	I-Application
controllers	I-Application
use	O
FAA	O
Order	O
7110.65	O
as	O
the	O
authority	O
for	O
all	O
procedures	O
regarding	O
air	B-Application
traffic	I-Application
.	O
</s>
