I rode the wrong route for a certification last year and need to fix it. Google Earth says it was about 8 m long the way actually run. Since the course was originally certified as a 5,000 meter course, can I use a percentage difference to adjust the Start? And that means NO calibration or recalibration.
Procedure: First, ride a part of the wrong route twice establishing beginning and ending points. Then ride the correct way twice. For safety sake, ride segment of wrong route one more time. If that agreed within .0008 of the worst of the first two rides then there is no reason for concern with tire expansion or deflation. Then multiply the % difference of the shorter rides by 5000 and adjust.