During the 2026 Chicago Marathon, runners noticed discrepancies between the official race distance and their GPS watches, partly due to city skyscrapers interfering with satellite signals.
GPS discrepancies in marathon
During the Chicago Marathon on Sunday, October 11, 2026, many participants noticed a noticeable difference between the official race distance of 42.195 kilometers and the distance shown on their GPS watches. Impact of urban architecture
Among the reasons for this discrepancy, the skyscrapers in the city center were a major factor, as they can interfere with satellite signals used by GPS devices. Race management challenges
This interference sometimes caused issues for race organizers, including difficulties in accurately tracking runners and ensuring fair competition. Runner experiences vary
Some athletes completed what they believed to be the full marathon distance, only to find out later that their GPS devices had recorded a shorter or longer distance due to signal disruptions. Official course remains unchanged
Despite these issues, the official course remains exactly 42.195 kilometers, as measured by the race organizers using traditional methods to ensure compliance with international standards.
