Why does the GPS distance not match the distance tracked on my local stride sensor or speed/cadence sensor?

GPS and independently tracked local sensor data should be very close, but if there is a discrepancy the sensor data is the most accurate. The GPS function on a smartphone can detect your location +/- 10 meters and then determines distance traveled based on changes in location. Trees, buildings, steep environments, and heavy cloud cover can distort GPS signals, resulting in errors in recorded distance and discrepancies between it and local data.