Contents: Recording a track

What’s a track?
Track point interval and nesting
Tracking affects battery life
Pause and resume tracking

What’s a track?

A ‘track’ is a series of points, recorded at frequent intervals by your GPS device, of your activity. eg A walk or bike ride.  Every track point recorded will include its location, date, time of day and elevation.

All good GPS handhelds will record a ‘track’. It is an electronic breadcrumb trail of your route.

Typically, you’ll see a track appear on the screen as it’s being recorded although you may have the option to keep it hidden. You don’t see the individual points, just a continuous line, your ‘track’.

Track point interval and nesting

A more sophisticated tracker will allow you to adjust how often the points are recorded.  They may be recorded after a fixed distance, a fixed time or a combination of both. Some will have an ‘automatic’ option which will attempt to make sensible decisions about when to record a track point, based on your motion. It might not record any points if you’re motionless, record points more frequently if you start moving fast and maybe record fewer points on a long straight section.

If you’re walking, it makes sense to record a track point based on a fixed distance. Then having a long lunch shouldn’t generate lots of unnecessary track points, all in the same place. Every 10m will give an accurate record of your day. That’s 1000 track points for every 10km you walk. Many Garmin handhelds have a limit of 10,000, that’s 100km. You’ll need to be very fast walker to fill that up in a day. Phones won’t be subject to the same limitations.

Recording a track point every 25m will still provide a pretty good track. 25m is only 1mm on a 1:25,000 scale map. A larger interval should stop any extra track points being recorded just because GPS isn’t perfect. eg If you sat still for half an hour eating your lunch and left a tracker running that was using a 1 metre tracking interval. It would likely record lots of different track points all in roughly the same place. A 25m interval should stop that happening.

If you do use a short track point interval like 1 second then be aware that normal inaccuracies inherent in an ordinary GNSS receivers will result in slightly different locations whilst you’re still. The resulting track will look a bit like a birds nest where you stopped. For that reason this effect is sometimes called ‘nesting’. Nesting could add significant distance to a track, so if you want an accurate record of your day distance-wise, then pause the track recording when you stop for any length of time.

If your app only allows the time interval to be adjusted then a track point every 10 seconds should provide a good record. The only way to avoid extra points being recorded over lunch is to pause the track, if that’s possible.

If you’re recording a track with a view to adding a new path or feature to OpenStreetMap then ideally, the track should be as accurate as possible. If you’ve got a dedicated handheld you should switch on everything that helps with accuracy. Multiple GNSS satellite constellations, dual-frequency, WAAS and EGNOS. A 1 second interval is a good idea. My little Garmin eTrex has a minimum distance interval of 0.01 km or 10 metres. However, the time interval setting allows for track points to be recorded every second, better. Just be aware that many Garmins won’t record more than 10,000 track points in a single track. eg That’s true of the eTrex, 64 and 65 series. If you do use a 1 second interval then you can only record a continuous track for just over 2 hours 46mins.

Many phone apps won’t offer any options and you get what you’re given. eg Outdooractive and OS Maps. Opening the recorded track files in a text editor should give you some clues as to how often track points are recorded.

Tracking affects battery life

Tracking can hit the battery on a smartphone hard. An app can’t record track points without using the GNSS receiver constantly and that uses a significant amount of power. The GNSS receiver will draw power even when the phone is in standby, with the screen off and the phone in your pocket. Phones vary hugely in how they perform. I wouldn’t recommend tracking with a phone anywhere that you need good navigation to stay safe, unless you’ve thoroughly tested it and are confident the battery will last.

Good phone tracking apps should be designed so that putting the phone in standby doesn’t stop the tracking. eg With Locus Map 4, even if you accidentally close the app, the tracking will continue unaffected. You must open the app again to stop the tracking.

Displaying a track on screen uses a little more battery than not showing it. If you don’t need to see it and can switch it off, then do.

If track points are recorded based on time interval then choosing an interval of a minute or more should allow the GPS receiver to be off some of the time. Your track won’t be so detailed but it will save battery. Only some phone apps provide any control over track point interval.

Dedicated handhelds and watches typically do much better whilst tracking and it’s not such a problem for the battery.

Pause and resume tracking

You could just start tracking at the beginning of the day and forget about it. At the end of the day stop the tracking, name and save the file. It’s simple, it works and you can forget about it.

However, your phone app or device will likely have an option to ‘pause’ the tracking. Pausing when you’re stopped could help with battery life and avoids false distance being added by ‘nesting’. If you were recording a track point every 2 seconds and then stopped for half an hour, the GPS receiver would waste battery recording 900 points in roughly one place. Pausing would be a good idea but it’s easy to forget to ‘resume’ (I find). When you do ‘resume’ a paused track, the newer track points are added to the same track. At the end of the day a single track file is produced.