You may have noticed that several apps running on the same phone might give slightly different distances. This is due to the way how apps handle GPS inaccuracies.
The most naive approach is to sum up the distances between locations that the GPS reports. Due to noise in GPS this locations can jump left and right of the actual path you take resulting in a distance that is longer than the real distance. Most of the GPS apps have some sort of filtering built-in to make distance more accurate but some don't.
The result are different distances reported by different apps.
With Argus we strive to provide the best accuracy. We filter the GPS signal so it makes sense. For example if GPS tells us that you are jumping from one side of the road to the other side every 5 seconds we'll assume that this due to GPS noise and not because you like to jump in front of cars. This sometimes means(especially when GPS signal is low) that the distance in Argus is shorter than in other apps. Especially if they use a more naive approach to calculate distance.
Tracking on a treadmill:
We calculate distance on a treadmill based on the number of steps you take. We recommend that you calibrate your running stride length in Settings if the distance reported in Argus is different than the one on the treadmill.
In general calculating distance from number of steps during a run varies widely from person to person and even in the same run session for the same person when you get tired. Runners tend to have a constant running cadence (steps per minute) and vary intensity and pace by adjusting their stride length. For that reason distance calculated from steps will never be 100% accurate but you could make it better by changing the stride settings to fit your average stride.