So one of our reader asked us this question the other day: Why do smartphone apps that use your location drain the battery immediately whereas some sportwatches can track GPS for hours with smaller batteries?
GPS Satellites send a relatively small amount of information to your GPS device, but they send it at a very low rate, 50bps (bits per second).
Your watch or purpose built GPS device has a small processor that can easily handle tracking and processing this data while consuming very little energy.
Your phone likely has a powerful, dual core processor that can’t go to sleep while you’re using GPS because it’s processing this tiny amount of data. It’s like using a 50 ton crane to move an car engine a few feet, a task that could easily be performed by a small pneumatic lift.
Poorly designed apps can add to this wasted load by keeping a bunch of other processes running as well, like checking for input from the microphone, downloading map data, etc. A well designed app can reduce the amount of wasteful processing when the screen is off, and ease the processing burden of GPS data as well. I’ve used fitness trackers on my phone for 8 hour bike rides, with the speaker calling out information every 5 miles, and the phone usually overheats long before the battery dies.