Synthetic vision systems: human performance assessment of the influence of terrain density and texture

The implementation of Synthetic Vision Systems (SVS) has posed a number of design questions. One of these questions is centered on the minimum required resolution of the Digital Elevation Model (DEM) database. Although a very detailed database may be desirable from a product appeal point of view or for improved representation of the elevation information., there simply may not be enough processing power available to render the high number of polygons with a texture at a high frame rate. Also, there may be a marginal rate of return of increasing DEM resolution when it comes to pilot performance, workload and situational awareness (SA). Another important issue is the choice of texture used on the synthetic terrain images. In the past, researchers and designers have debated about the relative merits of different textures (e.g., photo-realistic, elevation coloring, checkerboard). A third issue concerns the shading model, which may influence performance or SA through the potential for depth perception cues. The Operator Performance Laboratory (OPL) at the University of Iowa conducted a series of three experiments to assess human performance as a function of DEM resolution, terrain texture and shading methods. The DEM resolutions that were studied ranged from 3 arc seconds (best resolution) to 30 arc seconds (worst resolution). Textures included wire-frame (green on black), checkerboard, elevation coloring, contour lines, photo-realistic, and a non-textured plain brown color. Shading models included no shading, Gouraud shading, and flat shading. Part I involved an image identification task, in which the ability of non-pilot participants to recognize terrain features for static (Experiment 1) and dynamic terrain images (Experiment 2) was measured. Part II (Experiment 3) measured pilot performance by cross track error when na