IPhone – How precisely can I track distances using the iPhone accelerometer

The Nike+ GPS with a foot sensor has two sorts of input and can be more reliable than apps that only rely on GPS.

The main sources of foot sensor measurement error are:

• an odd gait (which will throw off the foot accelerometer - even when calibrated)
• incorrectly calibrated foot sensor
• your run routine typically covers several uneven stride lengths

You might be better with a foot sensor over a pure GPS application, but it's hard to tell in general.

I find the hassle of a foot pod not worth the extra accuracy and use GPS only apps. The best for me is made by Abvio. Their GPS apps are superb and allow detailed control. The only downside is this adds complexity to the UI and you need to know a little to operate the tuning controls properly. (I chose the Runmeter over Cyclemeter or Walkmeter since I like a red color and the shoe icon's looks - they are all exactly the same engine and you can use all of the settings on any app - you don't need more than one to get all the route types.)

The developer is very responsive to email support - I was getting errors on my motorcycle settings and they guided me to get the accuracy I wanted since each activity type has some assumptions that can cause errors for some users.

Depending on where and how you jog - this app allows you to tune and filter the raw GPS data to your liking. Since you can recreate this one path again and again, you should be able to get things dialed assuming it's not a problem with jogging in a canyon or under heavy tree / large buildings where interference and multipath effects will render all GPS faulty.

No. The app doesn't currently have an override and simply takes the distance units from the system settings.

It surely would be nice to have finer control, but the code isn't there to make a change today.