For me, markers are just one of the many visual clues available to see where the path is. I don’t see why we would want to have a key for path_visibility_if_there_were_no_markers for a marked trail. What is the usefulness of having this information? What’s the use case?
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As an American, I will admit I only learned about the SAC_scale because I saw the tags on hiking paths in Cyprus.
Keep in mind that OSM tagss doesn’t have the same meaning as the word use as key. This discussion can certainly not be summarised by a single word. Take ‘landuse’ for instance.
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As a humorous aside, this is like the old joke by Henny Youngman (20th century comedian):
“Take my wife…PLEASE!”
There’s a whole tome on OSM’s landuse=* waiting to be written, as indeed, it is a fairly complex topic. (Meanwhile, our wiki is pretty darn good).
To wit (and fully agreeing with @yvecai), keys in OSM are not what they appear to be as their literal meaning in English: OSM keys can be quite a bit more complex than that. (landuse=* certainly is).
So is trail_visibility!
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All of these keys have unintuitive names. I didn’t know trailblazing had a literal meaning related to hiking until I read the OSM wiki.
As a European I only learned about the SAC scale (that is, the Swiss scale) when I started learning about OSM. The scales differ between countries, and sometimes even within a country. For example I think most people who have hiked in Austria will know blue, red and black paths because that’s what’s on the signs. These are the same colours as for ski pistes, and this is probably not a coincidence. Even people who don’t ski usually know what a black piste is! So the colours are pretty intuitive and probably more widely known.
This is so interesting! So the word trail has different meanings even in different parts of the US.
Maybe unintuitive names are good. If sac_scale was hiking_difficulty=none/easy/intermediate/hard etc. then people would use it without reading the Wiki at all, instead the cryptic name encourages people to look up the intended meaning.
For what it’s worth I agree with the proposed changes but they only make sense if there is consensus on them.
There’s been multiple use cases lined above - for abandoned trails where path visibility and cairning are both poor to intermediate, or for ones where cairns/markers can be seasonally covered etc.
If current trail_visibility as a whole (mix of trail surface and makers) is all we need, then why do we have a separate trailblazed:visibility? Why is the visibility of markers in and of themselves important, but an actual physical path/trail unimportant??
Your argumentation would support the removal of trailblazed and trailblazed:visibility unless you can make a case for why they are more important than there being a physical visible trail surface as they are currently included in trail_visibility. Currently trailblazed:visibility is essentially trailblazed:visibility_if_there_is_no_trail
On my phone so no code wraps, but the point should still stand. At the very least it seems like if we’re keeping trailblazed having a trail_surface_visibility seems reasonable.
Apps rely
The issue is that the evolved usage and meaning don’t reflect the intention of the name (as per the creator as documented above) . It was meant to be the visibility of the trail itself, but including markers in it has morphed into a mix of both - so the current usage is the opposite of how it was created and IMO that deserves some clarification if it’s going to kept as is.
It is in no way different in Austria, neighbour to Switzerland. Nobody cares about SAC Scale. Apart from some OSM nerds. I bet, the Germans care no less. Both OEAV und DAV have a three grades system: blue=easy, red=intermediate, black=hard.
Only recently, some suggested to go with the Swiss in avalanche warnings. People in charge all declined - Much too complicated!
It’s a word that is used casually. I don’t think that I’m going for a hike on a highway=path in the forest, I think of a trail. In areas where terrain will hold a physical visible trail people will think of the trail as that mark on the terrain - in areas where the terrain doesn’t support that and a trail is only a set of markers, people will visualize what a trail means differently.
When I’m hiking on an abandoned or informal trail and it fades into invisibility I think of it as the trail not existing anymore. Sometimes (like where the John Muir Trail in Center Basin was before the early 1930s) a single track trail still is highly visible and easily followable, except in sections where there is more water and vegetation. I tend to dislike backcountry cairns (not those used on formally maintained paths) but built a large one where the trail disappeared for a few hundred feet / hundred meters near a stream crossing. In that case in OSM speak the path would still be visible, even if to me the trail is non-existent, and me creating a cairn to bridge that gap would make the trail visibility there excellent or good as the rest of it is easily followable.
It’s non-intuitive, but it’s also not entirely clear from a documentation standpoint that trail_visibility actually means trail_plus_marker_visibilty or path_visibility unless you read that markers can effect excellent or good. According the spec as markers do not contribute to intermediate, bad, horrible, or no.
A trail/path with no visible trail surface and trailblazed:visibility=intermediate should get trail_visibility=no as it is currently defined.
That’s why I suggested making trail_surface_visibility earlier to match the existing trailblazed:visibility (and the original intent of trail_visibility) and being more explicit with how trail_visibility is a mix of both markers and surface (which would mean adding marker information to intermediate, bad, horrible, & no) whether or not an alias of path_visibility is made or not.
Both keys, sac_scale and trail_visibility were derived from the Hiking Scale by the SAC. trail_visibility got split out of sac_scale very late in the proposal process. From the originalist point of view, trail_visibility tags the visibility of the path, what is there on the ground - regardless of marks and blazes. Thats how it is used in the SAC document.
Remember: When we here (Switzerland, Austria, Germany) say Route, we do not think of the OSM data type ordered-relation, but we mean the itinerary. So, when we say route markers, this need not be about knowing which path to follow at a crossing: That is what guideposts are for, the marks most often are just the same 
Route markers are to tell the route, no more no less. In remote areas, where not many people pass, so no path emerges, where terrain is pathless, they are essential.
Yeah, trail_visibility is bit of a mess, it makes sense it happened late and fast. The documentation even refers to markers in an inconsistent way see more in the second half of my reply above where an intermediate or lower trailblazed:visibility doesn’t affect it, only good and excellent.
I don’t see https://wiki.openstreetmap.org/wiki/Tag:information%3Dguidepost being used anywhere in the US, but seem like they could be useful. A few days ago I had to pull up topo to help an elderly couple on a dayhike that ended up at a junction of an informal and formal trails and were confused by the lack of signage.
For a pathless, marker less route, how are route markers handled in Europe, as a node network? I’ve come across some mapped paths in the southwest (example) where the majority of it is a handful for nodes strung together that create an arbitrary path line with no real impact on terrain. While I haven’t hiked that one, my partner and I explored around one south of there (just route finding with our eyes and topo) then tried following it on the way back and ended up at a 15-20 meter rappel down a dry waterfall. We saw one or two cairns the entire time, and maybe four footsteps, so it’s someone’s informal route they are trying to share. I’ve actually got a topic on this running on the #trails channel in the OSM slack channel at the moment.
The Swiss have organized their hiking network in a node like fashion on administrative governmental level. The SwissTopo map shows only routes where there are paths on the ground. They do not show routes where there are just markers. Most of the hiking routes have paths up to the demanding_mountain_hiking sac_scale value.
Not so in Austria or Germany. Hiking paths are managed by local organisations on their own thinking. There is a bit of governance, when tourism agencies want a special seal of quality. These are all paths on the ground. Many of them show in the ÖK50, the official map of the country.
Outside of this managed network, there are lots of paths in OSM that are mountaineering routes, they do not show in any official maps. In OSM they are often tagged sac_scale T6. There are notes in the area, where people that walked by did not see the path. Of course not! This is just a route out of a guide book with hundreds of routes, some blazed, some not, that somebody happened to drop a GPX of his ramblings there. But what can you do? It follows policy up to the letter, trail_visibility=no.
PS: I once argued on the principle of reproducibility. Little interest in that. I must say, I belong to the kind of people, that see paths everywhere. Very useful in remote areas. Not helpful in discussing OSM issues.
It would be kind of disheartening to learn, that these routes can be claimed “trail_visibility=excellent|good” in case the next cairn can be seen from the current one|has to be searched out for" (possibly loosing 100m height?)
This point keeps getting brought up on this thread, but is there anyone who actually uses the tag this way, or thinks that it would be a good thing if people used it this way? Don’t people just mentally fill in the blanks?
For comparison, here is how iD shows them (differences to Wiki highlighted):
Excellent: unambiguous path or markers everywhere
Good: markers visible, sometimes require searching
Intermediate: few markers, path mostly visible
Bad: no markers, path sometimes invisible/pathless
Horrible: often pathless, some orientation skills required
No: pathless, excellent orientation skills required
Effectively the iD tagging scheme has already implemented the suggestion of
This is probably a good idea if it prevents people from tagging every marked trail as good or excellent. The way they’ve done it is not ideal if you ask me, because if you take it very literally, it implies that any path with markers needs to be at least intermediate. I’m just copying it here to show that people probably don’t take the Wiki so literally, nor should they.
A few cairns spaced far apart are only useful on a sunny day and even then the path between the cairns may not be visible and that should be taken into account. That’s why I suggested that
In the real world, ignoring for a moment what the Wiki says, isn’t it more like this?
For comparison, the Wiki page on trailblazed is very explicit that the tag should not be used on route relations. I interpreted “describes trail visibility (not route visibility)” on the trail_visibility page the same way. But it’s perfectly possible that I’m the only one who was interpreting it like this!
But… shouldn’t that be the point of complete documentation? I’m not against trail_visibility being what it is now, but IMO some explanation of it incorporating both a trail surface and markers should be up top and not just in the ratings criteria.
That depends on how well it’s cairned. Silver Creek is an abandoned trail that is somewhat well (informally or many decades ago officially) cairned although there are times when cairns have fallen over or been destroyed be deadfall etc and the trail itself will disappear for hundreds of meters / thousands of feet at a time. IMO not an issue as I’m following a creek so w/e, but I added the following to that track. I suppose in an ideal world I would have tried to find every existing patch of trail and recorded where it started and stopped and made a bunch of segments to illustrate ground truth, but it was my first time doing it and we had a lot of ground to cover with more uncertain terrain ahead.
highway=path
name=Silver Creek Trail
ref=27E63
trail_visibility=horrible
trailblazed=cairns
trailblazed:visibility=intermediate
In this case trailblazed:visibility=intermediate means “next trail marker is sometimes visible and sometimes hard to find” which is true. trail_visibility=horrible means “Often pathless” which I took at the time to be the surface/visibility of the trail/path itself.
If I had to smush them into an overall trail_visibility it wouldn’t be intermediate despite there being some cairns - which is “Path mostly visible”, I’d go with bad “Path sometimes invisible, route partly pathless”. The trail surface is horrible, markers are intermediate, the path as a whole is bad.
It’s worth pointing out that “Path sometimes invisible, route partly pathless” to me doesn’t seem to indicate that it is referring to route relations. I read it as when the path you are on is sometimes not visible the route you are on is hence pathless. There are areas with no trail surface and no markers, which makes it a pathless route at times in my mind - that’s separate from larger routing issues.
On the trail_visibility page it just says This key describes attributes regarding trail visibility (not route visibility) and orientation. Route visibility to me is different from the visibility of the trail, and that’s not explicitly referencing to route relations (which path to take from a path). As we’ve beaten to death, it’s semantics, but if there are semantic differences or lack of clarity they should be addressed directly. There’s very knowledgable people that I’ve asked for help that had a similar interpretation as me in terms of mapping intermittent trails.
One thing I find interesting is a lot of people keep saying that we don’t need a trail_surface_visibility tag because trail_visibility covers that use just fine. trailblazed:visibility also falls under trail_visibility however, and I have yet to hear a strong case made for why marker visibility is more critical than the visibility of the trail surface itself.
It’s worth pointing out that trail_visibility=no as originally intended was probably meant to be used for paths that had some markers on them, not just for trails that don’t have any visibility. That seems like a case where the shift in meaning of the key has led to unintended consequences.
IMO those should be redone as node_networks with minimal key nodes vs “paths”.
I’m personally against creating paths out of random off-trail GPX recordings. A lot of times there might be a key section to an off-trail route, but the rest is pretty open to personal route finding and can change based on snow levels, etc. Having them there as a path just promotes the creation of more informal trails/erosion and people staring at their phone instead of reading terrain. Probably around half my backpacking is pathless and markerless, but I don’t think it’s appropriate to create an OSM path out of the routes I’ve taken even if they worked well. I’ve deleted a few paths that were pathless and markerless (and happened to have poor routefinding as well) that I’ve come across.
In regards to the principle of reproducibility there’s a big difference between seeing a possible route, and seeing a trail which has been caused by repeated traffic over the same location - that’s the “ground truth” where I would draw the line at making something an informal path vs node network of loosely spread out markers. This is getting pretty off-topic however.
I’ll copy and paste from a discussion elsewhere:
Having routes be a set of numbered waypoints would have some clear upsides:
- less impact created by people focusing on an arbitrary track and creating a trail where none existed
- less confusion by people that expect a trail when it shows up in a mapping client
- clarity that it is meant to be an XC route leading to some location (usually a peak or named feature)
I can easily see this getting out of hand - if people create node networks for every possible navigable path in the backcountry (like how some people create huge cairns to regularly mark a strong flowing outlet to a lake in a remote backcountry basin) the map becomes a cluttered mess of people “finding” routes that have been used for many decades in a fairly similar fashion.
IMO most off trail passes in the Sierra only need a top, a small minority need a bottom… but where is the bottom? it’s hiking up from a lake shore or something, or would that be the nearest trail, or would it be a final push to the ridge where things are steepest and it’s most critical to be “on route”? I would put the passes that need a middle node on one hand, but I’m also experienced at routefinding and others might want a node every couple hundred of feet.
For informal routes I’d be wary of marking cairns (there’s some XC cuts, like Simpson Meadow to East Pinnacles I’ve done three times, differently, none terrible, and encountered a few cairns each time lol) - I feel like there could be a good mentality of putting a few extra nodes on a route with a description field (after this pond turn right to stay on Class 2, don’t go down the grassy ramp for Class 4) but leave someone getting from the top of the pass to that midway point on their own - they can pinball from side to side looking for easier drops on shelves, or drop down more directly if they’re comfortable with simple unexposed climbing
I destroy hundreds of (non-digital) cairns a year and make less than 5. It has to be one weak area of an otherwise strong abandoned trail, or something informal where missing that one non-intuitive spot is a genuine issue of safety. Finger Col ledge being the only Class 2 option out of a Class 4 area felt fair to me (though I knocked down random branching ones below it I built up the existing cairn by the ledge) or the two Class 3 options out of Class 4 drops on Valor Pass I chose to leave the cairns undisturbed as I didn’t encounter any for what up to that point is “walk up, nearly anywhere, from nearly anywhere on the shore of this lake”. There could literally be hundreds of routes for the same off trail pass.
I personally rarely even share waypoints when writing up an off-trail route - I normally describe it and use photos, trying to abstract my experience into something general and being clear where decisions I made felt critical vs arbitrary. For example there’s a LOT of people that always go a certain way around a backcountry lake (10422?) up into Ionian Basin because Secor wrote it that way - the opposite shore worked quite fine and was more direct. 
I think it’s time to create a topic on this, if there isn’t one existing that can be revived.
@erutan It seems you’ve been reading the original description of trail_visibility on the wiki here Key:trail_visibility - OpenStreetMap Wiki while my proposal for a clarified text is on the wiki talk page here https://wiki.openstreetmap.org/wiki/Talk:Key:trail_visibility#New_text_proposal What do you think of the revised version? Is it better? Can it be improved?
When reading the original text, the reference to both path and markers confused me (and not only me). My first idea was that it makes logical sense to split these into path visibility and markers visibility, but the discussion here convinced me it doesn’t make practical sense. A map user would like to have an idea of what to expect from a path he sees on the map before he decides to take it: how (physically) difficult it is to hike (which sac_scale describes), and how easy it is to follow (not to get lost). With trail_visibility we are trying to describe the last. Here I don’t think it makes any practical sense to separate markers from any other visual clues: anything that helps to follow the mapped trail (the thin dashed line on the map is what I mean by “path” or “trail”) should be taken into account.
Until this discussion, I didn’t know this tag existed, I’ve never added it to the map, and maybe I won’t ever. But I can imagine a hiker would like to have some info on how easy it is to follow the itinerary he planned to follow by following the trail blazes. So trailblazed:visibility only really matters when he has to make a choice between different paths, i.e. at junctions. There it could be useful info (to know how much attention he needs to pay, to know how much time he might need to spend on finding trail markers and on walking down the wrong path, etc.).
Here I don’t think it makes any practical sense to separate markers from any other visual clues: anything that helps to follow the mapped trail (the thin dashed line on the map is what I mean by “path” or “trail”) should be taken into account.
I disagree, there is a difference. If the trail visibility is good and it refers to the physical path, one will expect to see it on aerial imagery, or similarly if it is bad to not see it. People will map accordingly. It should be clear what this refers to, and there should be a way to express whether the trail is visible on the ground
Aerial imagery fails for this. A trail can be very visible on the ground, but due to trees, not very visible from aerial imagery.
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