Figure 3.

The visibility of groomed snow in low contrast conditions may be improved by combining grooms of different periodicities. (a) The same shaded snow patch as in Figure 1(c). (b) The same patch again but enlarged such that its periodicity is four times lower than in (a). (c) The simulated hybrid groom, which combines the periodicity of (a) and (b). This groom pattern should be visible across a greater range of viewing distances than either component alone. (d) Improved visibility of the hybrid groom is demonstrated after scaling the original periodicity (top panel) and the hybrid groom (bottom panel) by 50%, equivalent to doubling the viewing distance. Whereas the groomed snow is rendered invisible in the top panel, it is still visible in the bottom panel, owing to the second, lower frequency groom period. Prior to combining, snow patches in (a) and (b) were spatially filtered such that their contrast energies are contained within independent frequency bands.