Investigation of Terrain Database Resolution Requirements (1992)
Research Objectives
Determine pilot preferences for terrain data resolution on electronic
terrain situational awareness displays. Vertical contour spacing as
well as horizontal resolution were studied. In addition, two display
formats were used: one showing terrain contours relative to Mean Sea
Level (MSL), and one showing terrain contours relative to ownship
altitude.
MSL Terrain Situational Awareness Display
(click on picture for full size)
Relative Terrain Situational Awareness (click on picture for full size)
Approach
Active line pilots interactively configured the horizontal and vertical
resolution levels of a terrain situational awareness display using the
MIT Advanced Cockpit Simulator. Flat, moderate, and steep terrain were
shown in plan view at 10, 40, and 160 nmi ranges on the Electronic
Horizontal Situation Indicator. Subjects configured the horizontal and
vertical resolution of the terrain data to preferred levels. The
aicraft's heading was then changed, and the pilots were timed to
determine if the route of flight was clear of hazardous terrain. The
subjects then estimated the minimum terrain clearance or the distance to
the hazardous region as appropriate.
Accomplishments
Pilots generally chose the highest available horizontal resolution, and
preferred 500' or 1000' contour spacing intervals. The mean response
time for subjects to determine whether the route of flight was clear of
terrain was significantly lower when using the ownship-relative display
as opposed to the MSL-relative display. Pilot preferences favored the
ownship-relative display over the MSL-relative display. There was no
significant increase in errors where subjects misread the display as
resolution was decreased.
Horizontal Reolution Preferences
Coutour Spacing Preferences
Response Time Results
Significance
Display reading error rates were not significantly correlated with the
resolution levels selected by pilots in this study, suggesting that
limits on resolution levels will be set by mission requirements and not
by human-factors issues. Strong preferences for 500' and 1000' contour
spacing suggest that these vertical resolution levels should be
available to the flight crew. The faster response times observed with
the ownship-relative display indicates that this display may be more
effective at providing pilots with an intuitive depiction of terrain
hazards than the MSL-relative display, at least in straight, level
flight situations. The MSL-relative display does have merit for uses
such as strategic planning for engine-out forced descents.
Publications
"Part-Task Simulator Evaluations of Advanced Terrain
Displays", SAE Aerotech '93 paper 932570, Costa Mesa, CA, September,
1993.
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