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Measuring Running Routes

This article explore some of the most common ways for measuring how far you’ve run run
and offers advice on how to get the most accurate results.

 

Tips For Getting The Best Accuracy

If plotting a route on a map:

  • Use the satellite map view
  • Zoom in to the maximum extent
  • Plot points carefully (don’t cut corners!)
  • Plot more points around curves than on straights
  • Use the “Snap to Roads” feature for road sections

If recording a route using a GPS:

  • Get a good signal lock before you start running
  • Stop recording as soon as you stop running
  • Avoid built-up or densely wooded areas if possible
  • Check the recording on a satellite map for errors

What level of accuracy should I aim for?

Before looking at the different options for measuring routes, it is worth commenting on accuracy in general.  Whatever method of measurement you use, it is virtually impossible to measure the exact line that you took around a route.  As a result, it is not unusual to get slightly different measurements each time for the same route and a small degree of inaccuracy is inevitable.  Therefore, when reviewing the distance of a run, we suggest that you always allow for a potential inaccuracy of around 0.5% in your measurements.  So, for example, for a route that is exactly 5 miles long, the distance you ran is likely be somewhere between 4.975 miles and 5.025 miles.

Even with the most accurate measurement methods, human error tends to account for most measurement errors, normally as a result of measuring a slightly different route to the one that was run.  So, to get the best accuracy follow our suggested tips.

 

Even with the most accurate measurement methods, human error tends to account for most measurement errors.

Different Methods of Route Measurement

 

1.  Jones Counter

This is the benchmark for accurate measurement of running routes and is the method used to certify the accuracy of many UK and International races.  A Jones Counter is a small device attached to a bicycle wheel that measures distance by counting the revolutions, or partial revolutions, of the wheel.  It is calibrated for use on a specific bike using a perfectly straight calibration course.  Jones Counters normally produce measurements that are accurate to within 0.1%.  You can find out more at the UK Road Running Course Measurement site.

 

2. Online Route Mapping Tools

There are a number of online route mapping tools available on the internet, including our Route Measurer on Good Run Guide.  These work by determining the latitude and longitude coordinates of each point plotted on the map and then using a distance formula to calculate the distance between each point.

To get the most accurate measurement, we recommend using satellite maps as these are real-world images.

Different map types are normally available and it is worth bearing in mind that some map types may not match exactly the real world, as paths and roads can sometimes be moved slightly from their real-world positions to make the map easier to read.  Ordnance Survey Explorer maps are a good example of this.  To get the most accurate measurement, we recommend using satellite maps as these are real-world images.  Like GPS devices, it can be difficult to measure accurately through wooded areas, where an aerial view of the path is obscured by trees, but unlike GPS devices, accurate measurement through built-up areas should not generally be an issue.

To test the accuracy of our Route Measurer, we measured four laps of a 400m athletics track using the satellite map view (see illustration below) and repeated the exercise 20 times.  The results varied by only 0.32%, with measurements ranging from 1598.344m to 1603.518m.  On all occasions, measurements were within 0.22% of the correct length with the majority being within 0.1%.  To achieve good accuracy levels though, it is essential to plot points carefully, ideally while zoomed in to the maximum extent.

 

Route Measurer Accuracy Test

 

3.  GPS Receivers/Watches

GPS devices work by measuring the time taken for signals to be received from a network of 24 satellites in space.  They work best when they have a clear view of the sky and need to ‘lock on’ to at least 3 satellites to work out your position.  They can also work out your height above sea level in a similar way but need to lock on to at least 4 satellite signals to do this. 

Unfortunately GPS devices are not infallible.  Even with a clear view of the sky, each individual position that is recorded is typically only accurate to between 3 and 5 metres, which can add up to quite a high potential error over a long route.

 

A wide range of GPS devices are available, with prices typically ranging from about £100 to £500.   Compared with other options, this makes them expensive but they are very convenient as they do everything for you.  As well as measuring your run, they record where you ran (not where you think you ran) and provide great instant feedback.  But unfortunately GPS devices are not infallible.  Even with a clear view of the sky, each individual position that is recorded is typically only accurate to between 3 and 5 metres, which can add up to quite a high potential error over a long route.  Even greater errors can occur when recording your height above sea level. 

The biggest GPS inaccuracies tend to occur in built up or densely wooded areas, as the signal can be delayed or prevented from reaching the GPS device.  However, even in the open, devices are subject to errors from variations in atmospheric conditions.  When a GPS signal is lost altogether, it results in the last two known positions being joined with a straight line, effectively cutting off any corners in between and producing a short measurement.  When signals are reflected off buildings, straight paths can be recorded with kinks, thereby resulting in a long measurement.  To illustrate this, the following picture shows an example of a section of a route recorded by a runner using a GPS device in central London.

 

GPS Signal Errors

 

We conducted a controlled test to assess the accuracy levels of popular running GPS devices.  The test was carried out on two different open air athletics tracks, each with a clear view of the sky, using two modern GPS devices.  Two runners recorded 20 separate measurements of a 1600m route by running four 400m laps of the track.  The results varied by 7.4%, with measurements ranging from 1571.693m to 1734.660m.  Most measurements were within 4% of the correct length but the most inaccurate result was 8.4% out.   

The following picture shows an example of one of the recordings.  The runner ran around the inside lane but you can clearly see that the recorded path often deviates from the correct position by around 3 to 5 metres.

 

GPS Accuracy Test Example

 

In most circumstances though, runners usually find that the level of accuracy is satisfactory for their needs.  Our advice is to always check that the route has been correctly recorded using a satellite map view of the route.  You can then make any adjustments as required by editing the route on the map.

You can read more about GPS inaccuracies in this excellent article on the Sources of Errors in GPS.

 

4. Pedometers

Pedometers are low cost devices, normally worn around the waist, that estimate how far you’ve run by counting your steps and using an average stride length.  Because this is a fairly simplistic method of measurement, high levels of inaccuracy are not uncommon.  Ghent University carried out a study on 1000 pedometers and found that most were inaccurate.  Three in four were over 10% inaccurate one in three were more than 50% inaccurate (SOURCE: BBC Report). However, accuracy levels can be improved by running at a consistent pace and trying to maintain a consistent stride length.

 

5. Footpods

Footpods are small devices worn in or around the running shoe that measure distance by detecting the motion of your foot. They use inertial sensor technology (accelerometers) to measure the acceleration of your foot each time you take a stride, so unlike pedometers, can adjust to different stride-lengths throughout your run.  They usually transmit the data to a watch-type receiver or some other device like a mobile phone.  Some manufacturers claim accuracy levels of up to +/- 1% after calibration. We have not tested these claims ourselves but anectodal evidence does suggest that they can be surprisngly accurate.  They have the advantage of not being dependent on any signal reception but, as they don't detect your location, they can't record the route for you; they can only tell you how far it was.  Some GPS manufacturers offer footpods as an accessory that can be used together with a GPS device to measure distance indoors, or anywhere else where you can’t get a good GPS signal.  They are also often available with some heart rate monitors that don’t use GPS technology.

 

Summary

Method Accuracy Level Guide
Jones Counter +/- 0.1%
Satellite Map Measurement +/- 0.25% [1]
Foot Pod +/- 2%
GPS Device +/- 4% [2]
Pedometer +/- 10% [2]
  1. Subject to accurate plotting of points
  2. Subject to singal reception.
  3. Subject to consistent stride length.

NOTE: These are indicative levels only from our own tests and manufacturer cliams. Differing levels of accuracy can be expected for different routes in different circumstances.

There are a number of different ways to measure how far you've run and each has different advantages. For convenience, GPS devices are great as they record the route for you but even with a good signal, accuracy levels can vary and in obscured areas signal loss can create quite large measurement errors.

Footpods enable you to measure your runs in any environment as they are not dependent on satellite signals. However if you want to see your route on a map you'll need to map it separately.

Satellite map measurement is very accurate provided you take care to plot the points in the correct place! This is normally easy to do but can be problematic through wooded areas.

As a guide, the table on the right shows indicative levels of accuracy using different methods. However, as it is almost impossible to measure the exact route you actually took, we recommend you always allow for a potential error factor of at least 0.5% regardless of which method you use.

 

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