Airport Traffic Control Tower
Siting Criteria: Visibility Siting
Analyses
William “Kip” Krebs and Glen Hewitt
ATO-P R&D Human Factors
[email protected] or [email protected]
Acknowledgements
The valuable contributions supporting this effort from the
following people are appreciated:
•
•
•
•
•
•
•
•
•
•
•
John Aschenbach
Rodman Bourne
Roger Bawgus
Dave Cloutier
Ronald Driggers
Bernie Garbowski
Rob Heckart
William Kaplan
Scott Iwamoto
Steven Murrill
Doug Norvell
• Kathy Peterson
• William Vaughan
• Atlantic City ATCT
Controllers
• Newark ATCT Controllers
• O’Hare ATCT Controllers
• Tulsa ATCT Controllers
• Las Vegas ATCT
Controllers
Visibility Siting Proposed Analyses:
Tower Siting Order Inputs
Object Distance and Discrimination: ATCT distance from critical airport
locations and ATCT height must support requirements for object visibility
from the ATCT cab. An Object Discrimination Analysis shall be performed to
assess observers’ probability of detection and recognition of an object on the
airport surface according to the criteria below
Observation
Capability
Requirements
Detection
Recognition
Observation
Description
Ability to notice the presence of an
object on the airport surface without
regard to the class, type, or model
(e.g., an object such as an aircraft or
vehicle). The observer knows
something is present but cannot
recognize or identify the object.
Ability to discriminate a class of
objects (e.g., a class of aircraft such
as single engine general aviation
aircraft).
Front View Probability
Criteria1 Minimum
95.5%
11.5%
Visibility Siting Proposed Analyses:
Tower Siting Order Inputs
Line of Sight (LOS) Angle of Incidence: ATCT distance from critical airport
locations and ATCT height must support requirements for viewing distant objects on
the airport movement areas, taxiways, and non-movement areas from the ATCT cab.
A LOS Angle of Incidence Analysis shall be performed as described in Appendix 5,
Section 2 to assess the angle at which the observers’ view of a distant object
intersects with the airport surface in accordance with the criterion below:
LOS Viewing Criteria
LOS Viewing Angle of Incidence
Minimum
Equal to or greater than 0.80 degrees
Two-Point Lateral Discrimination: Critical points of the airport surface operations
should be separated by sufficient distance to ensure that two objects at distant key
locations provide the observer sufficient lateral discrimination. The observer’s
viewing angle between the two points should be laterally separated by 0.13 degrees
(8 minutes) or greater.
The Impact of ATC Tower Height on
Visibility:
A First-Order Analysis
Steven Murrill and Ronald Driggers
(Army Research Laboratory - Adelphi, MD)
Problem Statement: What improvement in visibility
(detection, recognition, identification) can be gained by
increasing the height of an airport traffic control (ATC)
tower?
Visibility Analysis Tool
US Army developed a target acquisition sensor model to predict
soldiers’ ability to correctly detect, recognize, and identify
military targets. The model is based on over 50 years of electrooptic sensor, human performance, and vision research.
Human performance predictions are based on numerous human
performance field and laboratory tests.
Model Assumptions
Army’s Target Acquisition Model can be found at
http://www.hf.faa.gov/krebs/docs/ArmyTarget.pdf
Detection: Ability to notice the presence of an object on
the airport surface without regard to the class, type, or
model (e.g., an object such as an aircraft or vehicle). The
observer knows something is present but cannot recognize
or identify the object.
Recognition: Ability to discriminate a class of objects (e.g.,
a class of aircraft such as single engine general aviation
aircraft).
Identification: Ability to discriminate objects within a class
(e.g., C-172)
Model Assumptions
• Generate probability of discrimination curves using:
– Standard Target Transfer Probability Function (TTPF)1
– Modified Johnson’s discrimination criteria
– Effective number of spatial cycles on target (aircraft)
calculated by scaling the human eye’s Contrast Transfer
Function2 (CTFeye) by the atmospheric (optical) turbulence
modulation transfer function3 (MTFturb) at each range.
– A constant contrast transfer value for all ranges.
• Assess impact of tower height on visibility from the probability
of discrimination curves.
U.S. Army Night Vision Lab’s model
2 Barton’s model
3 Norm Kopeika’s turbulence model and the Tatarski height scaling model
1
Visibility Analysis Tool
Placed Model on Internet
Tool can be found at http://www.hf.faa.gov/visibility
Impact on Current and Proposed Towers
Object Discrimination
Object Discrimination (Detection)
Human Factors Tower Metric
(probability of detecting a front-view dodge caravan)
100
98
Probability of Detection
96
5 proposed towers (IAD, STL, CLE, ATL, IND) fall below criterion
94
12 current towers (IND, COU, DPA, GPT, FFZ, HVN, CLE, DET, JFK, MKL, FLL, STL) fall below criterion
92
90
88
86
Current Towers (Level 7 or greater)
Proposed Towers
84
82
80
78
0
20
40
60
80
100
120
140
160
180
200
Towers
Current Towers: provided by Tom Hilquest, Proposed Towers provided by AFTIL
Line of Sight Angle of Incidence:
Visual Perception Study
William K. Krebs and Glen Hewitt
(FAA ATO-P R&D Human Factors)
Problem Statement: What improvement in an observer’s
perspective of the airport surface (as represented by the
ATCT line of sight (LOS) angle of incidence to designated
key points on the airport surface) can be gained by
increasing the height of an air traffic control (ATC) tower?
Methods
Participants
• 11 male and 1 female tower airport traffic controller
specialists (TUL, ORD, ACY, NEW) volunteered to
participate in the LOS study.
• Average age was 46.3 years with a standard deviation of
8.8. Average operational airport tower experience was
17.4 years with a standard deviation of 9.3.
• Observers participation was approximately 1 hour in the
AFTIL simulation cab.
• Observers signed informed consent.
Methods
AFTIL Tower Cab
• Observers performed common ATC visual tasks at different
tower heights while positioned in a 3600 tower cab software
simulation. Observers were positioned 23’ from the screen.
• Realistic airport scenes were simulated using 1 (need to
verify) meter resolution images.
• Image generation was set at 64 pixels per inch on the
screen which is equivalent to 20/40 visual acuity.
• Key-points were located within 10,000’ of the observer to
ensure maximum number of polygons assigned to each
object.
Methods
Stimuli
Airport
Name
Key Point
Distance to
Key Point
(feet)
Tower Heights (feet)
values below were not corrected for key point elevation
Number of
Observations
Per Question
Per Height
RIC
Rwy 34
Threshold
9590
40, 94, 140, 186, 232, 277, 323, 369, 415, 461
39, 90, 100, 123, 143, 160, 170, 206, 290, 374
9
3
MEM
Rwy 36R
Threshold
9809
119, 158, 197, 236, 275, 315, 354, 393, 432, 471
120, 140, 150, 179, 210, 265, 280, 307, 351, 436
9
3
LGA
Rwy 31
Threshold
4350
129, 130, 140, 160, 167, 205, 213, 243, 281, 319
3
FWA
Rwy 05
Threshold
8960
153, 175, 216, 240, 294, 372, 450, 529, 607, 686
3
MMU
Rwy 23
Threshold
4907
84, 108, 122, 151, 165, 194, 237, 280, 323, 366
3
MSP
Rwy 30R
Threshold
9665
58, 103, 148, 193, 238, 284, 329, 374, 419, 464
9
CPS
Rwy 30R
Threshold
7063
30, 64, 99, 133, 167, 202, 236, 270, 305, 339
9
OSH2
Rwy 36
Threshold
6550
45, 75, 105, 136, 166, 196, 226, 257, 287, 317
9
Methods
Procedure
• Each observer was exposed to five towers at ten different
tower heights. Observer’s task was to visually scan a
designated distant “key point” on the airport surface and
rate his ability to (1) distinguish boundaries of the
movement areas and (2) identify position of target at the
airport’s key point.
• MD-80 was located on the key-point.
• Participants vocally responded using a 6-point Likert Scale.
• Airport towers were blocked and tower height was
randomized for each subject. To avoid order effects, each
participant received a different order of airport towers and
tower heights.
Methods
6-Point Likert Scale
Question 1: How well can you distinguish boundaries of the movement areas?
0
1
2
3
4
5
Can not see
runways or
taxiways.
Can see target
area. Can not
discriminate
boundaries of
runways or
taxiways.
Can discriminate
boundaries of
most of runways
and taxiways; but
provides no
distance
information.
Can discriminate
boundaries of all
runways and
taxiways, but
unable to estimate
distances between
movement areas.
Can discriminate
boundaries of
runways and
taxiways, and
provides some
information about
distances between
movement areas.
Can discriminate
boundaries of
runways and
taxiways, and can
readily estimate
distances between
movement areas.
Question 2: How well can you identify position of target at the airport’s key point?
0
1
2
3
4
5
Unable to
determine any
information about
target’s position
Can see target
object. Unable to
determine any
information about
the target position
relative to key
point or
movement areas.
Able to
determine the
general target
position relative
to key point, but
unable to
determine if
target is on or off
movement area.
Able to determine
that target position
is in general
vicinity of key
point, but unable
to estimate
distances of target
within movement
area.
Able to determine
that target
position is near
key point, and
provides some
information about
distances of target
within movement
area.
Able to determine
the exact target
position relative to
key point. Able to
readily estimate
distances of target
within movement
area.
LOS Angle of Incidence Study
Question 1: How well can you distinguish boundaries of the movement areas?
6 point Likert Scale, TUL,ORD,ACY,NEW controllers (n=12), Subject rating ≥ 2
Tower air traffic controllers response to the distant key point - “Can discriminate boundaries of most of runways
and taxiways; but provides no distance information.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 0.481.
LOS Angle of Incidence Study
Question 2: How well can you identify position of target at the airport’s key point?
6 point Likert Scale, ORD,ACY,NEW controllers (n=9), Subject rating ≥ 3
Tower air traffic controllers response to the distant key point - “Able to determine that target position is in general vicinity of
key point, but unable to estimate distances of target within movement area.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 0.799.
Line of Sight Angle of Incidence
Method and Results
Question 1: How well can you distinguish boundaries of the movement areas?
0
1
2 = (0.48 degrees)
3
4
5
Can not see
runways or
taxiways.
Can see target
area. Can not
discriminate
boundaries of
runways or
taxiways.
Can discriminate
boundaries of most of
runways and taxiways;
but provides no
distance information.
Can discriminate
boundaries of all
runways and
taxiways, but
unable to estimate
distances between
movement areas.
Can discriminate
boundaries of
runways and
taxiways, and
provides some
information about
distances between
movement areas.
Can discriminate
boundaries of runways
and taxiways, and can
readily estimate
distances between
movement areas.
Question 2: How well can you identify position of target at the airport’s key point?
0
1
2
3 = (0.80 degrees)
4
5
Unable to
determine any
information about
target’s position
Can see target
object. Unable to
determine any
information about
the target position
relative to key
point or movement
areas.
Able to determine
the general target
position relative
to key point, but
unable to
determine if
target is on or off
movement area.
Able to determine that
target position is in
general vicinity of key
point, but unable to
estimate distances of
target within
movement area.
Able to determine
that target
position is near
key point, and
provides some
information about
distances of target
within movement
area.
Able to determine the
exact target position
relative to key point.
Able to readily
estimate distances of
target within
movement area.
Line of Sight Angle of Incidence Criterion established at 0.80 degrees
Impact on Current and Proposed Towers
Line of Sight Angle of Incidence
Line of Sight Angle of Incidence
Human Factors Tower Siting Metric
(subtracted 27 feet for all towers)
Proposed Towers
Current Towers (Level 7 or greater)
Line of Sight Angle of Incidence
3
2
1
0.80 degrees
0.58 degrees
0
2005Tower Order .8 deg criteria
1972 Tower Order 35' criteria
0.8 degrees (48 min) LOS criterion
0.58 degrees (35 min) LOS criterion
102 (52%) current towers below criterion
58 (30%) current towers below criterion
1 proposed tower below criterion
3 proposed towers below criterion
-1
0
20
40
60
80
100
120
140
160
180
200
Towers
Current Towers: provided by Tom Hilquest, Proposed Towers provided by AFTIL
Impact on Current and Proposed Towers
Line of Sight Angle of Incidence
Line of Sight Angle of Incidence
Human Factors Tower Siting Metric
(subtracted 27 feet for all towers below 130 feet)
4
Proposed Towers
Current Towers (Level 7 or greater)
Line of Sight Angle of Incidence
3
2
1
0.80 degrees
0.58 degrees
2005Tower Order .8 deg criteria
0
1972 Tower Order 35' criteria
0.8 degrees (48 min) LOS criterion
0.58 degrees (35 min) LOS criterion
50 (26%) current towers below criterion
17 (9%) current towers below criterion
1 proposed tower below criterion
3 proposed towers below criterion
-1
0
20
40
60
80
100
120
140
160
180
200
Towers
Current Towers: provided by Tom Hilquest, Proposed Towers provided by AFTIL
Two-Point Discrimination
Purpose: Quantify the impact of tower location on observers’
ability to discriminate two distinctly spatially separate points
on the airport surface.
Criterion: 8 minutes
Calculate angle
Backup Slides
LOS Angle of Incidence Study
Question 1: How well can you distinguish boundaries of the movement areas?
6 point Likert Scale, TUL, ORD,ACY,NEW controllers (n=12), Subject rating ≥ 3
Tower air traffic controllers response to the distant key point - “Can discriminate boundaries of all runways and taxiways,
but unable to estimate distances between movement areas.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 1.067.
LOS Angle of Incidence Study
Question 1: How well can you distinguish boundaries of the movement areas?
6 point Likert Scale, TUL,ORD,ACY,NEW controllers (n=12), Subject rating ≥ 4
Tower air traffic controllers response to the distant key point - “Can discriminate boundaries of runways and taxiways, and
provides some information about distances between movement areas.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 1.428.
LOS Angle of Incidence Study
Question 1: How well can you distinguish boundaries of the movement areas?
6 point Likert Scale, TUL,ORD,ACY,NEW controllers (n=12), Subject rating = 5
Tower air traffic controllers response to the distant key point - “Can discriminate boundaries of runways and taxiways,
and can readily estimate distances between movement areas.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 2.177.
LOS Angle of Incidence Study
Question 2: How well can you identify position of target at the airport’s key point?
6 point Likert Scale, ORD,ACY,NEW controllers (n=9), Subject rating ≥ 2
Tower air traffic controllers response to the distant key point - “Able to determine the general target position relative to key
point, but unable to determine if target is on or off movement area.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be.
LOS Angle of Incidence Study
Question 2: How well can you identify position of target at the airport’s key point?
6 point Likert Scale, ORD,ACY,NEW controllers (n=9), Subject rating ≥ 4
Tower air traffic controllers response to the distant key point - “Able to determine that target position is near key point, and
provides some information about distances of target within movement area.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 2.177.
LOS Angle of Incidence Study
Question 2: How well can you identify position of target at the airport’s key point?
6 point Likert Scale, ORD,ACY,NEW controllers (n=9), Subject rating = 5
Tower air traffic controllers response to the distant key point - “Able to determine the exact target position relative to key
point. Able to readily estimate distances of target within movement area.”
Based on this response criteria, the minimum tower observation to key point line of sight angle should be 2.187.