Anyone who has used a phone GPS app to track a ride or run will be familiar with the problem of rogue data points, which are created where the GPS signal is temporarily lost. Where this happens “bridging” data points may be created by the app, to “track” the missing section. While these rogue points have little impact on the overall time and average speeds for the session, they may suggest you have travelled into some distinctly odd places (I apparently did a pirouette in the rock face of a tunnel once, and on another occasion appeared to cycle backwards and forwards across a bay); they also tend to produce impossibly high top speeds (121.5 km/h is challenging on a cycle on a flat road).
While it is not worth worrying about minor discrepancies, any major oddity could be worth addressing. So I searched the interweb for a utility which edits GPX files (the export format typically used by tracking systems) to remove the rogue data points, and produce a more accurate record.
I found what I was looking for (GPS Track Editor: a free utility which does what I need – more about that in a separate post), but also came across an online service which offers some added extras.
MyGPSFiles also offers a means of editing imported GPX files, but it can also generate a “replay” of the imported track in a quasi-3D format, using a Google Earth plugin.
Intrigued I imported the GPX file for Day 2 of the Great Taste Trail, and, after a couple of false starts and refinements of the system settings, generated a 10 minute replay of the ride. The replay also includes an “Elevation profile” with a moving marker, which enhances the understanding of the trace.
Note that this does have some limitations: the motion is jerky (a result of the periodic GPS sampling) and the Google Earth 3D rendering is variable – particularly in more obscure parts of Tasman Bay – but the end result is readily followed, and does prompt memories.
For example, sorting through Dale’s photos I came across one with a couple of horse riders approaching us, and a second (immediately after this) travelling along a coastal track. For the life of me I could not place either – until I followed the replay of the track in MyGPSFiles. Both were taken shortly after leaving Mapua following breakfast, where the trail takes a sharp right around the edge of a plantation and heads back to the coast.
MyGPSFiles does allow these 3D tracks to be shared for up to 30 days, but does not currently allow them to be saved permanently. That limitation is readily overcome by using a screen recording facility. The addition of some on-screen markers, and library music clips, and we have a lasting memento of the trip.