What to do if there is a significant distance error or no trajectory after outdoor sports? Why does the Xiaomi Smart Band 9 outdoor sports require maintaining a Bluetooth connection on the phone?

Please upgrade to version 1.1.122 and above.
Due to the lack of independent positioning function, the positioning information and trajectory data of the band come from the mobile phone. Therefore, this type of outdoor sports requires opening the mobile phone's positioning information and connecting it to the mobile phone for use.
For your reference, here are the methods to enable mobile location information:
1. Before using the band for outdoor activities, on the Android phone, you should select the positioning permission of the Mi Fitness APP as [Allow] or [While Using the App], and turn on [Enable Background Unrestricted] on the Device interface. Otherwise, there will be no movement trajectory and the distance will be inaccurate after the exercise ends. When the positioning permission is set to [While Using the App], or when the Mi Fitness APP is in the background, there will be a large error in outdoor exercise distance or there will be no trajectory after the exercise ends.
2. Before using the band for outdoor activities, on the iOS phone, you should select the positioning permission of the Mi Fitness APP as [Allow]. And go to [Settings] >> [Mi Fitness] >> turn on [Background App Refresh], or there will be no movement trajectory and the distance will be inaccurate after the exercise ends.
When the positioning information of the mobile phone is turned on normally and the track is displayed in the exercise record of the Mi Fitness APP, but the distance still deviates, you can zoom in on the track of the exercise record to see if there is a long straight line in the exercise track. This phenomenon could be caused by obstructions around, resulting in deviations in the positioning information of the mobile phone, which in turn causes deviations in the distance calculation of the band.