The (In)visibility of Groomed Ski Runs.

William J Harrison

doi:10.1177/2041669519842895

Abstract

I analyse the visibility of “groomed” ski runs under different lighting conditions. A model of human contrast sensitivity predicts that the spatial period of groomed snow may render it invisible in the shade or on overcast days. I confirm this prediction with visual demonstrations and make a suggestion to improve visibility.

Highlights

Moments before I ‘‘stacked it’’1 while snowboarding on Cougar Alley, Big White Ski Resort (Canada), I appreciated that the blue run was as much a challenge for my contrast sensitivity as it was for my aching thighs
I could not establish whether this close match between the spatial frequency of groomed snow and peak contrast sensitivity was coincidental or by design: Patents only describe an operator’s ability to see outside the grooming vehicle but not the visibility of the groomed snow itself (e.g., Brandt, 1989)
The model predicts that sunlit snow is visible at all spatial scales, but that shaded snow is only visible within the midrange frequencies

Summary

Introduction

Moments before I ‘‘stacked it’’1 while snowboarding on Cougar Alley, Big White Ski Resort (Canada), I appreciated that the blue run was as much a challenge for my contrast sensitivity as it was for my aching thighs. The high contrast of groomed snow at 1.5 cyc/deg corresponds well with the peak human sensitivity to grating stimuli (e.g., Watson & Ahumada, 2005) and natural images (Bex & Makous, 2002).

Results

Conclusion