How fractal complexity distorts distance and elevation gain in trail and mountain running: The case for course measurement standardization
Journal
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology
ISSN
1754-3371
Date Issued
2025-05-21
Author(s)
Raimundo Sanchez
Pascal E Egli
Kilian Jornet
Michael Duggan
Type
journal-article
Abstract
This study investigates how fractal complexity affects Trail and mountain running (TMR) race course measurements at varying GPS resolutions and emphasizes the need for standardized course measurement protocols. GPX files from 34 UTMB World Series race courses, including final events in Chamonix, were analyzed. Horizontal distance, elevation gain, km-effort, and fractal complexity were computed at varying GPS spatial resolutions (0.2–100 m). Elevation data were refined using a 20-cm resolution Digital Elevation Model (DEM) to ensure consistency across the dataset. The courses were systematically resampled and compared to assess the effects of spatial resolution on race measurements and classifications. The findings reveal that a decrease in GPS spatial resolution significantly reduces measured distances and elevation gains. Discrepancies in kilometer-effort reached up to 14% (mean = 7.0%, SD = 3.8%), horizontal distance up to 6.3% (mean = 2.9%, SD = 1.5%), and elevation gain up to 32% (mean = 14.0%, SD = 9.5%). Adopting a 1-m resolution, chosen for its practical balance between capturing terrain complexity at a human scale and computational efficiency, would enhance the reliability of distance, elevation gain, and km-effort calculations, ensuring fairer race classifications and improved comparability across events.
Subjects
calibration
;
curricula
;
distance measurement
;
course measurement
;
digital elevation model
;
elevation data
;
fractal complexity
;
gps accuracy
;
measurement protocol
;
mountain running
;
race classification
;
spatial resolution
;
trail running
;
fractals
;
course measurement
;
gps accuracy
;
mountain running
;
race classification
;
trail running