Human Factors in Information Displays
I. Key Idea: Display Design Process
A. The display design process should begin with:
1. Cognitive Task Analysis: Systematic analysis of the psychological factors that affect an operator’s performance in a situation.
2. Information Needs Analysis: Analysis of what information the operator needs to accomplish the task.
II. Fundamental Principles of Information Displays
A. Principle of Need
1. Give operators what they need to know, when they need it.
2. Corollary: If the information isn’t needed, don’t provide it.
3. Example (classic): Map of the London Underground
i. Actual Geography
a. Contains more information than subway user typically needs; additional information makes literal display hard to use
ii. Schematic Representation
a. Real world distorted and additional information eliminated so that users have information they need and only that
B. Principle of Legibility
1. In general, dimensions of information ~ dimensions of representation
2. Visual Displays
i. Display size
a. large enough for details to be easily resolved
ii. Contrast & Brightness
a. adequate for all levels of illumination and glare
iii. Color
a. distinct differences for different information
3. Auditory Displays
i. Loudness
a. loud enough to be easily heard over ambient noise
ii. Clarity
a. static low enough to make sounds/speech distinct
iii. Frequency
a. distinct differences for different information
4. Example: National Weather Service (NWS) Map Clutter
i. Black & White map attempts to display too much information on a single display with only one dimension of variation
ii. Map clarified by elimination of information and addition of color
C. Principle of Display Integration/Proximity
1. When mental integration or comparison is required, displays should be proximally located.
2. Aviation Examples
i. Primary Flight Instruments
a. Originally, instruments were placed anywhere there was space
b. Modern (post-WW II) arrangement places basic six instruments used for primary flight control together in a standard arrangement
ii. Standard Instrument Navigation Instruments
a. To navigate, need information about current position and direction relative to known position(s)
b. Directional Gyroscope (DG) displays heading information
c. VOR/Localizer Indicator displays deviation from selected course to/from radio beacon
d. DME displays distance to radio beacon
e. Instrument Landing System (ILS) requires display of altitude (glide slope) information
iii. Horizontal Situation Indicator
a. Combines information from DG and VOR/LOC indicator
b. May also incorporate information from DME
c. May also incorporate glide slope information
iv. Instrument Landing System
v. Standard Instrument Navigation Instruments
D. Principle of Pictorial Realism
1. Representation should resemble information it depicts.
2. Examples
i. Physical resemblance
a. Old style attitude indicator (AI) had completely symbolic display
b. New style attitude indicator (AI) depicts sky as blue, ground as brown
ii. Metaphorical resemblance
a. Depth display Tufte (1993)
b. Using stark color contrast to show altitude/depth yields a garish, unnatural display that is difficult to interpret
c. Using subtle, natural colors (shades of blue for depth, brown for altitude) yields display that is easy to interpret
E. Principle of the Moving Part
1. If it moves in the real world (or the operator’s mental model of the world) it should move in the display.
2. AI with moving airplane and fixed world easier to use, yields fewer errors, easier to learn than AI with moving world and fixed airplane (Roscoe, 1968)
F. Principle of Predictive Aiding
1. When the operator must anticipate future states, the display should indicate those states whenever the prediction is reasonably accurate.
2. Example: Flight Director
i. Displays current state of aircraft (as in traditional AI) and how aircraft should be maneuvered (place wedge in chevrons) to produce desired state
G. Principle of Discriminability
1. Different types of information should be easily discriminable.
2. Example: Weather depiction problem
i. Turbulence, Storm, Icing displays use same colors to display different information – intensity in some cases, probability in others
III. Summary Examples
A. TCAS
1. Integrated information
2. Pictorial representation of 3D location of targets relative to aircraft
3. Trend information for predictive aiding
4. Auditory warnings
5. Auditory resolutions
B. ATC Display
1. Integrated display
2. Trend information
3. But is 2 dimensional representation with 3rd dimension digital
C. Airbus PFD
1. Integrated information
2. But:
i. Speed tape on right
ii. Altitude tape on left
iii. Pitch up (towards higher numbers) for speed to go down.
iv. Ground moves, aircraft is stable
D. Cirrus General Aviation Instrument Panel
1. Legible
2. Pictorial
3. Discriminable
4. Integrated information displays
i. Moving map
5. But
i. No predictive aiding
ii. Standard inverse moving AI
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