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Does anyone know of any iPhone app that tracks distance accurately ? I tried a couple and I'm amazed how lousy they are (some are reporting distances over twice as much etc)

Basically I would be using it when I'm jogging around the neighbourhood (non-linear distance of course). I want to measure the distance I have jogged.

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What apps have you tried? It sounds a bit unlikely that a GPS based one could be 100% off. Also what's the inaccuracy measured in meters? –  Gerry Sep 7 '11 at 16:53
    
My wife uses Runkeeper and Wahoo simultaneously, and they report different distances for the same run (as much as 10% different). How do you know which one is correct? You know what they say about a man with two watches? –  Paul Tomblin Jun 17 at 12:52
    
@PaulTomblin, Uhm.. what? –  Pacerier Jun 17 at 17:03
    
If you have one watch, you assume the time it's telling you is correct. If you have two and they disagree, you don't know which is right, or indeed if either of them is right. So gaining a second watch makes you less certain of the time rather than more certain. –  Paul Tomblin Jun 17 at 17:06
    
@PaulTomblin, Why can't you take the center? That's bound to be more accurate than either one. –  Pacerier Jun 17 at 19:02

7 Answers 7

up vote 4 down vote accepted

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.

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I've been very pleased with RunKeeper on my iPhone 4, and my wife has been very disappointed with it on her 3Gs. We can only conclude that the GPS gear on the 4 is better than the 3Gs, though I don't recall that being in any of the marketing goods.

When we run together, her phone routinely shorts us by maybe .1 mile every mile or so. But mine seems dead accurate. Same app, same version.

The conclusion is, the app doesn't have that much to do with the accuracy of the captured distance.

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+1 for runkeeper. I use it when cycling, hiking etc, and it's been fantastic. iPhone 4 only for me tho, I dont have a 3GS. –  Nic Wise Sep 12 '11 at 17:15

This may be one of those questions where there is not a definitive answer.

While it is up to each app developer to know how to better track, add and store each translation delta, how to determine the delta itself is up to the hardware, not the app. Location-aware apps use the same location-aware hardware and iOS' internal libraries via the Core Location API's.

What this means is that not because an app is lousy in your neighborhood, that means that it will consistently be lousy everywhere else. It ultimately depends on how much information Core Location has available: Your phone will try and use triangulation to determine your translation deltas by looking at where things like cell phone towers and Wi-Fi hotspots are located. If all of this fails, then it will rely on the actual GPS-provided location.

Again, this is all independent of which app you are using. So if you are in a location where there are not many Wi-Fi hotspots or where cell phone towers are not within reasonable reach, then you may want to use the Nike+ app--the one that does not use Core Location. This app requires you to have a Nike+ shoe with a transmitter. I have both apps and the shows with the transmitter and they measure distances around my neighborhood in a reasonably similar way. Hope this helps.

UPDATE:

A good source to understand how the iPhone location services work is by reading this article. I was wrong in stating that GPS is a fallback mechanism. Instead, the Wi-Fi and cellphone tower data assist the device in getting an initial location faster, before starting the actual GPS tracking. The reason for this is that the initial tracking is the most time and resource consuming operation. So GPS is still used at the end, just not right away.

I believe the original point still holds: As the article states, your actual location may determine how well the device performs when using location hardware services. And because that is beyond the control of individual apps, I think that the same app may not perform the same way when compared to other apps in the same place versus a different place. That is why I think that this question cannot have a definitive answer that tells us that an app is truly always better than another one.

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I think you are wrong in believing GPS is the fallback, as it should be checking the GPS first. Do you have a source to your claims? –  Gerry Sep 7 '11 at 16:49
    
My source was what I remembered from having read this article: macworld.com/article/159528/2011/04/…. I am wrong in that GPS is a true fallback. The Wi-Fi and cellphone tower data assists the device in getting an initial location faster, before starting the actual GPS tracking. The reason for this is that the initial tracking is the most time and resource consuming operation. So GPS is still used at the end, just not right away. Hope this clarifies the technical aspect. –  Christian Correa Sep 7 '11 at 18:32
    
My understanding is that when a program asks LocationServices for locations, it specifies how accurate it needs that information, and then LocationServices determines whether it needs to fire up the GPS or if the wifi/cell data is accurate enough. So maybe the reason we're seeing different distances from two apps running simultaneously has to do with how accurate the data they're asking LocationServices for is? –  Paul Tomblin Jun 17 at 12:50

My app of choice when it comes to GPS tracking is Kinetic GPS (iTunes link). From my answer to this question:

It's described as a swiss army knife for GPS tracking and I tend to agree. I had originally bought it to track backwoods bike rides but quickly found myself using it for all kinds of tracking: walks, runs, even car drives.

They have a modular approach to configuring the application. You can slice and view the data in all kinds of ways thanks to the pluggable interface. Analyze it over time for peaks, overlay it on a map. Very cool stuff.

And important to me: you can export your data in one of three common formats.

I use it to map the mountain bike trails in my neighbourhood and find its accuracy is excellent, even at higher speeds, as long as it has a strong enough signal from the cell towers (the satellite signals in the trees tend to fall off pretty quickly). When I get to the fringe service areas its accuracy drops off. But that would be the case for any GPS app.

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I have used Cyclemeter (equivalent to Runmeter) a lot when riding, and have played with a few other GPS loggers. The problem with all these apps is not that they are inaccurate themselves; it is that they are reliant on the underlying iOS Location Services, which is what reports your current position to all those apps. Sometimes the GPS system on your phone just freaks out for a few seconds (or more) and you wind up with some very unrealistic data. I know that the Abvio apps will report how much time of your workout is spent with an unreliable signal (Location Services reports the radius of confidence along with your current location to the apps—sometimes that radius is measured in kilometers). I know that dealing with dodgy data consumes a lot of development resources for the companies producing these workout-loggers. In short, I'd say "don't blame the apps."

There are a number of apps, including Runkeeper and Kinetic, that can interface with ANT+ devices through a gadget called a Fisica dongle. This would let you monitor heart rate and footfalls, which (I think) could be used by these apps as a reality check on your GPS track.

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I'm not a jogger, but I've made fairly good experience with RunKeeper for cycling. It's not extremely accurate either, but it was always sufficient for me. The free Light version will be fine for almost all uses.

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If you want to check if it fits your needs, I use Motion X GPS Lite (which, like most of the Lite apps, it's free).

Main limit of the Lite version is being able to save only 1 track at time. Which is enough for me. However, the PRO version is available on iTunes Store.

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weird it's only for hungarian –  Pacerier Sep 8 '11 at 6:13
    
You're right, I am sorry. I downloaded it years ago and I thought it was still available worldwide so I linked the result from a Google Search ... It seems they pulled the Lite version from other stores and left only the MotionX GPS "standard". –  maggix Sep 9 '11 at 16:23

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