Optimize power consumption during trips

[shankari]

We already use geofencing to minimize power consumption when the user is not taking a trip. However, once we have exited the geofence, we read the location and the activity continuously. This leads to excessive power drain in situations where the user is travelling all day.

We should tune the location and activity detection parameters during trips by tweaking the time and distance parameters to get the location less frequently during long trips and more frequently during short trips. For example if an automobile is driving at freeway speeds, we can turn off tracking until the next exit (Kalman filter?)

[shankari]

One initial implementation might be to set a distance filter based on the speed. Basically, we want to get data roughly every 30 seconds apart.

This is particularly important because the iPhone does not have a time based filter on the location tracking - only distance. So we need to simulate a time filter based on the distance filter and the speed.

Question: Why can't we just use a fixed distance filter? Why do we need to have an adaptive filter? Claim the issue to get the answer :)