What is, "Motion Calibration" and why is it always running?

I think I might be able to answer this now, although it may be a little late in coming. The reason this setting was introduced was probably not to determine how many steps you take, but to correlate it more specifically to your distance. It must have been introduced when Apple started work on the Watch and realized they couldn't put GPS into it to measure distance running.

Instead, blurbs on Apple's site say that the watch learns what your stride is based on a few runs with your iPhone. Because there is no third-party app the Watch can tap into in order to measure this, this setting must have been placed there in order for a user to be able to have these measurements ready for when they do purchase and pair their Watch with their iPhone. The Watch would then be immediately able to access both walking and running distance that had been measured more accurately by the iPhone for months. If you deactivate it, you can still get a very accurate step count, but the distance is a guesstimate based on your height. With Location Services enabled, Apple can measure distance much better, and this aids the fitness experience in the Apple Watch.

No, the M8 co-processor is very power efficient.

Go through this online help:

https://help.apple.com/iphone/8/

Not helpful. Doesn't have anything to do with "motion calibration" in location services running 24 hours a day.

Another thread at motion calibration is asking this same question, so far without an answer.

Motion Calibration is used by the new processor chip to gather movement metrics. For example, how many steps you take or stairs you climb. If you are not interested in any of the health apps collecting your data then you can disable this feature.

Open up the compass app and recalibrate it. That should prevent motion calibration from using your location too often.

The only features i have enabled under System Services is 'Find my iPhone, Location Based Alerts and Motion Calibration. I also chose not to share my location. You can disable that from Settings/Privacy/Location Services/Share My Location. See if that helps out.

I have done compass calibration but still seeing Motion Calibration constantly using location services.

You're right. I noticed that too. :/

Well iOS 8.0.2 was just released so I'm downloading it now and hoping it fixes the issue 🙂

Apparently Apple stores up to 7 days of your motion data like walking/running distance, steps taken and flights climbed. All of that information was automatically synced to the Health app after I upgraded to 8.0.2. That would explain the constant GPS use. I'd just disable it if you have no use for the Health app.

II'm not sure if this is an ios 8 bug or not, but the solution proposed in this thread worked for me:

iPhone 6 Motion Calibration Always Using Location Services

Just turn 'locations services' off and on again and it fixes the problem! It's been doing it all week on my iPhone 6+ but doesn't seem to have had much impact on battery.

I think that when the icon is active this can indicate a wide variety of enabled location services, from full GPS tracking, to just using wifi / cellular signals to get a rough estimate. It could perhaps even have just even been a bug that showed the icon whenever the m8 was active.

anyway, this made the icon go away, and my health kit data is still appearing and being tracked.

Are you connected to wifi? I've noticed that my gps indicator is on due to the motion calibration whenever I am not connected to wifi.

I know the phone's ability to determine your location is more accurate when you're connected to wifi. If you're not connected to wifi it may need to run the gps more often to accurately determine your location.