Climbing Route Difficulty Grade Prediction and Explanation

This article focuses on sport climbing and on the design of innovative tools for supporting climbers to browse and search routes to climb. The difficulty of a route, its grade, is normally assessed by expert climbers, named route setters. A regular climber, after trying a route, may perceive it more or less difficult than the route setter. It is important to estimate this climber's perceived difficulty of the routes in order to suggest the routes that have a target perceived difficulty as expected by the climber. We develop a knowledge-based approach that uses domain-specific features to train a predictive model. Additionally, the problem is modeled as a rating prediction task in a recommender system, using a matrix factorization approach with a custom normalization solution. The knowledge-based approach enables us to develop a grade prediction explanation functionality. In off-line experiments, we demonstrate improvements over a baseline. Moreover, we show how the proposed techniques can be exploited in an app developed by a major company offering information services to the sport climbing market.