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Design considerations for a helmet-mounted synthetic degraded visual environment display

Piloting helicopters in degraded visual environments (DVE) remains one of the major challenges for the next years. While some research concentrated on the specialized problem of brownout landing, low visibility conditions in general cover a broader range of scenarios that further includes night, glare, fog and mist, as well as combinations of those. Project ALLFlight is DLR's initiative to diminish the problems of piloting helicopters under such circumstances. A possible solution comprises the use of sensors that are able to sense the environment even if the pilot cannot effectively see anything. As part of the project display symbologies are being developed to enable the pilot to make use of the rather abstract and noisy sensor data. In a first stage sensor data from very different sensors is fused. This step contains a classification of points into ground points and obstacle points. In a second step the result is augmented with ground data bases. Based on an earlier implementation of a synthetic head-down display an implementation for a head-tracked, helmet-mounted system is being developed. Since color is presently not yet an option for head-up displays, alternative symbologies have to be considered, including variations in transparency, density of terrain displays and size and shape variations for obstacle representation. In this paper we present the basic techniques used for obstacle and ground separation. We choose a set of possibilities for the pilot display and detail the implementation.