What is the Indoor option?
When the product is set to Indoor mode, it will measure indoor activity such as walking or running on a treadmill. In Indoor mode, GPS positioning is disabled and the product does not record measurements that require GPS signals, such as your workout route. The product uses the built-in stride sensor instead to record measurements.
Note: To ensure that your measurements are as accurate as possible, perform GPS positioning outside at least once before using the product indoors. Wait outside for at least 15 minutes with no obstructions overhead after you complete GPS positioning, and keep the product still as you wait. The product will compare data from the stride sensor with this GPS data to record more precise measurements.