Updating GPX Trackpoints

Project Leader: Bob Palin, Utah Coordinator, bobp@discoverytrail.org

Terminology:

  • Trail – on the ADT a Trail is a continuous section of the ADT within a state, some states have more than one trail, Colorado has three, the northern route in CO, the southern route in CO and the western part of the route in CO. There are currently 20 Trails on the ADT. In this usage ADT Trails are not related to the various hiking trails that the ADT uses.
  • Segment – Each Trail consists of multiple Segments, a Segment usually travels between significant locations, cities, or geographically significant points, etc. Some Segments are ‘alternate’ segments which provide a route avoiding some obstacle to a type of travel. Bicycle routes for instance avoid places where bicycles are not allowed or where it would be impractical to ride. There are currently 153 segments on the ADT.
  • Waypoint – each segment consists of multiple Waypoints, a waypoint is a significant point on the ADT, though the significance can vary greatly from the St Louis Arch to a cairn on a mountain! (The latter may be more important when you are trying to find your way over a mountain in the clouds…) Waypoints are intended to help navigate and also provide information about their location, they are represented in the GPX as real GPS waypoints, each waypoint is also listed in the Turn By Turn documents (TBT). There are currently 4,200 waypoints on the ADT
  • Tracks – tracks are strictly a GPX item, there is one track for each segment.
  • Trackpoints – each track consists of many Trackpoints, trackpoints are simply points that get joined together to make up a line representing the ADT on a map. They are created either by recording with a GPS unit or by drawing with GPS mapping software. They are similar to waypoints but only have location and elevation information. There are currently 122,000 trackpoints on the ADT.

The Issue

In the ADT GPX files there are two sets of information, the Waypoints and the Trackpoints, they are not specifically related in any way so they can, and have, diverged over time which leads to navigation problems.

The Solution

The new database of 2020 gives us a chance to connect the two sets of data, each waypoint will be associated with a trackpoint east and west of it. Unfortunately deciding which trackpoints belong to which waypoint is a complicated task that can only really be achieved manually. With over 4,000 waypoints it is daunting project that we can only hope to finish in 2020 through the help of volunteers. It’s a rather tedious job, though you do get to look at a lot of maps and learn about the ADT.

A system has been created where people can easily find waypoints that are not yet integrated into the tracks and enter the information needed to do that by looking at a map showing the track and the waypoints. We don’t provide the map, we provide a small GPX file that can be displayed on the GPS program of your choice.

There can be a lot of trackpoints (blue) between each waypoint (purple). Displayed on Viking GPS (free)

One issue you may come across is a grouping of redundant trackpoints, this is usually an artifact of the the GPS recording. It’s good to minimize the number of trackpoints so two of these three could be deleted. Be careful though that none of the deleted points are ‘attached’ to waypoints!

Pointless trackoints