[SOLVED] A few newbie questions about cycle tracks in OSM


When downloading the GPX files of cycle tracks available in OSM through WayMarkedTrails, I notice a few oddities:

  • No timestamps

  • Some segments (trkseg) go backwards

  • The tracks aren’t in the right order, ie. not continuous

  • A lot of segments only contain a few points, ie. they could be merged into a single segment

I’d like to know why that is, and what I can do to get a clean route.

Thank you.

If you look at last week’s questions, you will find I gave quite a detailed explanation of what is going on with cycle routes on OSM. However:

What would a time stamp mean. OSM is a description of the world at the current point in time. If you want the tool to assume some arbitrary start time and date,a and a particular cycling speed, you should raise that as a feature request against WayMarkedTrails.

Unless you tell us which route you were trying to output, I can’t be sure if whether the backwards sections are a bug in WayMarkedTrails, or an error in the data entered into OSM.

As to mis-ordering, whilst it is best practice to define a route relation in the right order, one cannot physically do that if there are one way sections. Also it is not uncommon to define a route with forks, although defining multiple routes and a route_master relation is probably better, not that that would help you, as it is the route_master that is really what would be named on the map. WayMarkedTrails should be taking your nominated starting and end points and finding a sorting a path between them.

I don’t know what constitutes a segment in WayMarkedTrails, but OSM routes are lists of ways. Every different road will be a way, but many roads are further split because they have different attributes. If you want WayMarkedTrails to merge multiple ways, you should raise a feature request, against WayMarkedTrails.

Looking at your question from last week, one of the routes you seem to be interested in is: https://www.openstreetmap.org/relation/416471

Firstly, could I ask anyone in DWG or the French community reading this to check the sourcing of the is route, as quoting a URL as a source rings alarm bells, especially when the only copyright notices on that source say reproduction is forbidden. Normally, approved sources for OSM will have short names that can be found in the wiki.

That route definition has a branch, at the bottom, which means it is impossible to define a single ordering for the route. It also has one way sections, e.g. https://www.openstreetmap.org/way/294310647 which again mean there is no single unique path (unless you define the direction of travel).

It is actually sorted quite well, so should be easy to fix up into the correct order, except for the branch at the bottom. There are conventions as to the correct order for one way sections: list everything in the forwards direction, in forwards order, then everything in the reverse direction but in reverse order of traversal.

As an example of a sorting error that does exist, https://www.openstreetmap.org/way/294310647 and the next way with the same name are in the wrong relative order. (Also, if I understand the name correctly, it is wrong. I think it says tow path, which is a description, not a name. If that is the case, it should not have a name tag.

What has really gone wrong here though is that, in three places, someone has added whole routes, not just the ways that make up the route. That is not allowed by the wiki, and nor do either JOSM or the www.openstreetmap.org seem to understand that. The sub-routes aren’t even in their correct relative positions in the overall route.

Although I could fix these, I’m concerned that I might be compounding copyright violation by doing so.

In case anyone hasn’t seen it, have a look at the “I’ve seen a problem; what should I do?” section of http://wiki.osmfoundation.org/wiki/Data_Working_Group .

Basically if you can, try and ask the mapper themselves (via changeset discussion comment) about the potential problem - ask them what the source is (in their own language if possible). They may be able to explain why its addition is valid, or might not know what sources are valid. If that doesn’t work or isn’t possible please contact the Data Working Group, preferably by email on data@osmfoundation.org.

Posting comments to a seemingly unrelated forum question is akin to “on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying ‘Beware of the Leopard’” (c) Douglas Adams.

I suggest using a better combination of tools to produce a useable track.
I use gpsies.com, and there are many other worthwhile choices too, and it gives me the ability to make my tracks using a multiple lists of osm type maps plus google maps.
Because my use is always cycling or hiking, I normally use with GraphHopper and Sigma Cycle + Hike Bike Hills + Waymarked Trails selected as a guide. I can then start plotting my track initially with ‘Follow roads’ selected and use the osm ways for the route. For parts of the route which are inadequately mapped or if I go off-track I can deselect ‘Follow roads’ and plot that choice.
Or I can use the Google routing engine and a choice of the Google maps offered for sections of the track.
Finally I can add waypoints along the route and save the track for download to my gps.
This gives you far more options than just trying to download a route from from one map. It is often helpful to have other maps with way-marked trails or other in the browser to assist this process.
As you suggest it would be much better if you could more readily download a useful tracks from some sites and we all hope for improvement in this area.
just my 2c

Unfortunately, whenever I look closely at the map, which tends to happen with the questions here, I tend to find things that look as though someone was more enthusiastic about getting them on the map that about copyright compliance. If I followed them all up, I would be spending a lot more time researching the source, finding the changeset (this relation is on version 209, so a simple request for the history exceeds the limits of the web site), and generally building the case than actually answering the question.

The real choice is between flagging the issue here and ignoring it.

(However, in this case, I’ve used the API to find the changeset and have now added a comment, albeit in English, as my ability to write French is rather worse than my ability to read it.)

Thanks much for the infos, and sorry for posting twice.

In this particular case, I wasn’t interested in plotting my own routes, but rather downloading official routes as seen on OpenCycleMap.

So the bottom line is: Those routes as seen through Waymarked Trails are usable, but aren’t always as clean as well-done routes available from eg. tourist information offices or serious contributors to OSM. Caveat emptor.