Transformers

Transformers are small (or big) transformations that are applied to your GPX track after it has been uploaded. This allows Fietsboek to provide some common, simple editing options, without users having to do that themselves.

All transformers are optional and disabled by default. You can enable transformers when uploading a track on the bottom of the page. You can also enable transformers for already uploaded tracks in the editing view.

Note

When enabling transformers for already existing tracks, your browser might not show the changed track. Try force-refreshing (Crtl + F5) the page so that it reloads the GPX from the server.

In other applications, transformers are sometimes called “filters”. That term however has many different meanings (like the filters on the “Browse” page), and as such, Fietsboek calls them transformers.

Keep in mind that the transformers provide a “quick and convenient” way to apply a predefined set of changes to a track. If you need to do fine-grained edits to a GPX file, you need to use a different tool and edit the file before uploading it to Fietsboek.

Fix Null Elevation

The fix null elevation transformer removes points at the start and end of a track that have a “wrong” elevation. This helps to avoid issues when GPX trackers don’t have elevation data yet and fill in 0, leading to wrong uphill calculations and wrong diagrams:

An elevation graph that starts at 0 and makes a jump to 165.

Activating the transformer will produce the following track:

The same track, but with a fixed elevation graph that starts at 165.

The transformer considers “wrong” elevation to be either points that have an elevation of 0, or points that have a slope of more than 100% to the next point.

To fix those points, the transformer will find the first correct point, and copy its elevation to the wrong points.

Fix Elevation Jumps

The fix elevation jumps transformer eliminates big elevation jumps in the middle of a track. This is useful to deal with “stitched” GPX files, where the elevation is consistent within a single track, but the absolute value might not be correct (e.g. if the device recalibrates):

The elevation profile having a big jump in the middle.

In this track, the device was re-calibrated mid-track. The transformer will adjust the elevation values:

The same elevation profile with the jump removed.

The detection of jumps work similarly to the fix null elevation transformer, with the difference that it works in the middle of tracks. It will consider the earlier points as anchor, and then adjust the later points such that the first point after the jump has the same elevation as the last point before the jump.

Remove Breaks

The remove breaks transformer removes longer breaks of inactivity by deleting the points and shifting the following points back in time. This is useful e.g. if you are waiting at a single spot for a while, and you would like that to be removed for a cleaner log.

Note that this transformer modifies the track’s timings. Therefore, the recording will end earlier than it did in reality, and the stopped time will be reduced.

A break is removed if the speed is below 1 kilometer per hour (approx. 0.28 meters per second) for more than 5 minutes.