Preliminary Evaluations of Advanced Terrain Depiction Methods (1991)
Research Objectives
1. Determine effectiveness of current terrain depiction methods.
2. Evaluate two candidate advanced electronic terrain displays.
3. Evaluate a proof-of-concept graphical Ground Proximity Warning System
(GPWS).
Spot Elevation Display (click on picture for full size)
Contour Display (click on picture for full size)
Approach
Two part-task simulator studies were performed using the MIT
Advanced Cockpit Simulator. In the first study, active line pilots
from autoflight equipped aircraft flew approaches using paper and
electronic prototype instrument approach charts which depicted terrain
using current spot elevation symbology. ATC vectors through terrain
were issued in several approaches, and pilot awareness of the terrain
hazard was monitored. In the second study, pilots used either an
electronic spot elevation terrain display or an electronic smoothed
contour terrain display during approach. Vectors into terrain were
again issued, and pilot awareness was observed. In addition, a
proof-of-concept graphical GPWS display was shown to the subjects to
obtain their comments.
Accomplishments
Two distinct modes of terrain information use were identified: Terrain
Situational Awareness involves terrain depiction on large range scales
(above 10 nmi) and is used for strategic planning purposes, while
Terrain Alerting depicts terrain on small range scales (< 10 nmi) when
immediate maneuvering is required to avoid a hazard. In the first
study, pilots successfully detected and avoided terrain hazards in only
3 out of 52 cases (6%). This low hazard recognition rate is thought to
be due to high levels of confidence in ATC clearances and highlighted
the fact that current terrain depiction methods appear to be inadequate.
In the second study, hazard recognition rates for the spot elevation
display (20%) and the smoothed contour display (25%) were comparable
when pilots assumed that ATC was providing adequate terrain clearance.
Once the pilots were aware that they could not rely on ATC to provide
terrain separation, the hazard recognition rate increased to 62% for the
spot elevation display and 93% for the contour display. Pilots were
unanimously in favor of the contour display, and were receptive to a
graphical GPWS system.
Hazard Recognition Rate
Effect of Aircraft Symbol on Hazard Recognition
Significance
The lack of effective terrain information in the cockpit combined with
the high-quality ATC system in the U.S. seems to have led pilots to
abrogate the responsibility of terrain clearance to ATC. Current spot
elevation symbology was found to be less effective in presenting terrain
hazards to pilots than a smoothed contour presentation. Advanced
terrain displays appear to be an effective means by which flight crews
can monitor terrain separation without reliance on ATC.
Publications
"An Exploratory Study of Plan-View Terrain Displays for
Air Carrier Operations", The International Journal of Aviation
Psychology, 3(1), pp 39-54, 1993.
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