GPX track extensions
QLandkarte GT is able to process data in extensions fields of track points in GPX file. Those extensions fields can be displayed
- in the tabular view of the track edit dialog,
- as time series graphs, and
- as tooltips of a track point in the map display
This page contains the user documentation. The GPX track extensions Internals page contains related documentation for QLandkarte GT software developers.
GPX Extensions file format
A GPX file is based on the XML standard which encloses information enclosed in tags like this:
GPX provides a lot of tags to store GPS data, such as position, elevation and many more. Furthermore you can add even more data with the “extensions” tag. Arbitrary tags can then be placed inside the extension tag:
<extensions> <name>value</name> </extensions>
The content of your extension can be what ever you like, whether text or numbers. So it is possible to give a wide range of additional information to every track point in the GPX file.
Here is an example for a track point extended with arbitrary extensions:
<trkpt lat="49.0441283333333" lon="12.098445"> <ele>329.5</ele> <time>2010-04-11T17:02:44Z</time> <extensions> <nmea:UTC>2010-04-11T17:02:44Z</nmea:UTC> <nmea:gps_speed>18.5714444444444</nmea:gps_speed> <nmea:baro_ele>331.6224</nmea:baro_ele> <nmea:ele_diff>-2.12</nmea:ele_diff> <nmea:gps_head>337.5</nmea:gps_head> <nmea:compass_head>296.4</nmea:compass_head> <nmea:head_diff>41.10</nmea:head_diff> <nmea:gps_err_hor>6.4</nmea:gps_err_hor> <nmea:gps_err_ver>7.2</nmea:gps_err_ver> <nmea:gps_err_sph>9.7</nmea:gps_err_sph> </extensions> </trkpt>
If you use the extensions with namespaces (such as “nmea:” in the above example) they should be defined in the header section of your GPX file like this:
<?xml version="1.0"?> <gpx version="1.1" creator="nmea2gpx" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:nmea="http://qlgt.org/nmea" xmlns="http://www.topografix.com/GPX/1/1" xmlns:gpxx="http://www.garmin.com/xmlschemas/GpxExtensions/v3" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd">
Display in Track Edit Dialog
QLGT will display any extension it finds in a GPX file in the track edit dialogue. Select which extension to show in the tracklist in the settings tab:
Extensions are listed in the track list view as columns which can be moved and sorted:
Display as Time Series Graph
To view the extensions as a plot over the time, simply click on the extensions button
Any extension with valid content (i.e. content that can be plotted over time or distance) will then appear as a tab in the plot window above the track editor. Like the other graphs, they can be zoomed in and out of.
Display as Tooltip in Map Display
The extensions data can also be displayed in the hovering info box that appears when you move your cursor over a track point