GPX (GPS Exchange Format): how to open it and how to create a route

GPX is a simple XML format for exchanging GPS data: waypoints, tracks and routes. It is understood by Garmin and Wahoo navigators, bike computers, sports watches, the OsmAnd and Komoot hiking apps, the Strava service and just about any program that works with tracks.

OpenStreetMap maps are exported to GPX in order to move features into a device or an app: points of interest become markers on the navigator screen, linear features become lines you can walk or ride along. This is the most direct path from map to device, with no converters in between.

The file is a single .gpx: point features are written as waypoints, lines and polygon outlines as tracks. The name is taken from the feature's name in OSM, and the remaining tags are folded into the description as key=value pairs. Coordinates are WGS84 with six decimal places, roughly ten centimeters on the ground.

What the format does not do: elevations at points are not filled in, area features arrive as outlines only, and a track is geometry rather than a plotted route with turns. The device will show the line on screen, but the turn-in-two-hundred-meters prompts are built by the navigator itself from its own data.