Implications of sac_scale=strolling

Road_Runner · 2024-11-18T22:10:31.979Z

This is for example 16° incline:

mapillary.com

Mapillary

Street-level imagery, powered by collaboration and computer vision.

This is 10° incline (left path):

mapillary.com

Mapillary

Street-level imagery, powered by collaboration and computer vision.

I used for both paths strolling, cause they are both walkable without obstacles and with crutches or strollers but it’s not a flat terrain.

Hungerburg · 2024-11-20T22:18:36.345Z

Road_Runner:

Perhaps we can agree on a value and record this in the definition?

The number six came from some (DIN) standards on accessibility. Those even allow ten percent for short sections (10cm on ramps/wedges?).

When sac_scale talks about terrain, I never know: do they mean the path or the surrounding terrain? Mind you, the pictures on the OSM wiki show no paths apart for the value hiking, all other grades go over pathless terrain; So likely, path and terrain synonymous.

My guess: When the sac_scale documentation talked about “slightly inclined terrain”, the path is meant. Otherwise, “falling hazards properly secured” would not mean much.

PS: Re-sharing Darum wurde die SAC-Wanderskala nach 20 Jahren überarbeitet has fresh SAC® pictures. I guess they support the single file language present since a recent change to the documentation, might be represented with width=* too? The hiking picture only presents slight incline.

Road_Runner · 2024-11-22T16:34:51.410Z

supsup:

In general I would say incline should be under 10 % or so.

I have noted this in the wiki. Seems to be a good guideline where you can still move well with strollers and crutches and there are apparently no objections to this.

rhhs · 2024-11-30T11:42:02.637Z

I think it’s not necessary or even desirable to mention incline at all. Assuming sac_scale is used for hiking, users would use a map with contour lines from which incline can be deduced. So incline can be separated out of sac_scale. In practice, there will be a correlation between sac_scale and incline (higher sac_scale paths are often steeper, and vice versa), but I can imagine that there are sac_scale=strolling that are quite steep, just like there are sac_scale=alpine_hiking paths that have no incline.

Hungerburg · 2024-11-30T21:36:01.840Z

HikingPathModestIncline1920×1080 379 KB

Brouter has detailed hill shading, but the calculations use coarse SRTM. See BRouter web client

Distance down 185m altitude lost 16m. Maximum incline 13 to 15% in short sections. Watching people walk there, some visibly breath heavier than on flat terrain. “Steep” sections quite short, obviously even such modest incline requires a bit of effort: People obviously lean forward into the “hill”. Youngsters stroll down with ease.

If I fully understand, strolling was introduced to widen applicability of sac_scale and cover the desires of people that do not want to “hike” and do not use maps with contour lines and hill shading.

rhhs · 2024-12-01T09:24:49.666Z

What I mean to say is that so far, the other sac_scale values do not take steepness into account, only technical difficulty and exposure. Maybe we should keep it that way also for the new value, and accept that “strolling” should sometimes not be taken literally. sac_scale is then like “smoothness for pedestrians”: only the roughness of the surface should be taken into account.

Vinzenz_Mai · 2024-12-01T10:20:20.822Z

supsup:

In general I would say incline should be under 10 % or so.

I’ve got the same point of view. There should be a recommandation (not a hard value) for a maximum incline. I wouldn’t see a way with an incline of 15% as “strolling” anymore. 10% for small sections could be tolerable.

rhhs:

sac_scale is then like “smoothness for pedestrians”: only the roughness of the surface should be taken into account.

I don’t see it that way. It should be taken more literally than that. It should really be pathes that are really easy to use without much effort.

rhhs · 2024-12-01T11:27:44.937Z

Vinzenz_Mai:

without much effort

What matters here is the definition of “effort”. So far it has been the effort of feet (and sometimes hands, arms, etc.) to cross the terrain safely, without taking the effort to gain or loose altitude into account.

Hungerburg · 2024-12-01T23:45:46.259Z

Personally, I’d not fight against calling walking that section of St. James Way a stroll rather than a hike. Yet, I am neither a hiker nor a stroller; I myself can cope that modest incline decently. I just observe people walking, up or down.

BTW: I also observed sac_scale=demanding_mountain_hiking getting used above sac_scale=mountain_hiking to indicate steepness of paths in mappings, where I could not see any technical difficulties. But that is just what I observed in the past, way before openstreetmap decided to deviate from the source of what the tag originally wanted to convey and instead do its own thing. So yes, I think, steepness also played in back then.

rhhs · 2024-12-02T07:08:00.688Z

Hungerburg:

I also observed sac_scale=demanding_mountain_hiking getting used above sac_scale=mountain_hiking to indicate steepness of paths in mappings, where I could not see any technical difficulties.

I think that is a tagging mistake, and I would edit it to sac_scale=mountain_hiking if hands are not needed for balance.

It’s worse when someone maps a trail as sac_scale=hiking because there is no elevation change while it is actually hard-going. We hiked the Lycian Way in Turkey last weeks, and found long sections of coastal path that were quite hard (max. 2 km/h, constantly watching your footing) but were tagged as sac_scale=hiking. Some were as hard as this path A closer look at the rocky coastal path between Limanağzı and Boğazcık [503] [A4] – Trekopedia (which is correctly tagged with sac_scale=demanding_mountain_hiking).

supsup · 2024-12-02T12:25:17.912Z

Steepness of the terrain has always been a part of the specification. Sometimes these tags are used very unappropriately, using T5 for something that is T2-T3.

I do agree that steepness should not be a determining factor, I see it more as a circumstance. T4-T6 will rarely no be steep, unless you are traversing something very vertical horizontally.

Not sure how to go about it - I think the wiki is already well documented and that is how it should be done.

SomeoneElse · 2024-12-02T12:57:58.906Z

supsup:

Sometimes these tags are used very unappropriately, using T5 for something that is T2-T3.

Rather than saying something like that can you instead say “which OSM tags” and “which OSM values” are used inappropriately, and what they are used inappropriately for. If you say “T5” to most people, even in OSM, they’ll probably just think that it is a type of Volvo car.

supsup · 2024-12-02T13:01:09.638Z

demanding_alpine_hiking four mountain_hiking, wrongness probably (I do not know why people choose those values) due to steepnes. Never heard of such a Volvo car, I am happily almost oblivious about that abominable invention:-D.

Another source of confusion can be official designation. In Argentina, they use colours I think three or four, but the main distinction seems to be length and elevation difference, all the trails overed by it were mostly hikin or mountain_hiking. Somebody might have try to do 1 : 1 mapping to sac_scale, when at least two of their grades corresponded with one sac_scale grade.

Hungerburg · 2024-12-02T23:04:39.246Z

SomeoneElse:

Rather than saying something like that

I also think, the column “Equivalent SAC scale based on Swiss Alpine Club” should be removed from the fine article. Especially, if openstreetmap wants to emancipate. Any takers? I am tired of sentences like “But on hikr.org Großglockner is a T2”.

supsup · 2024-12-03T01:01:24.340Z

Well, there is still the mention that in Switzerland and that part of Austria where it is officially used, it should actualyl adhere to the official grades.

yvecai · 2024-12-03T10:42:24.988Z

Then let’s start to remove that: OSM is global, if a local community wants to have local definitions, they can specify it elsewhere. And in the present case, that’s almost stating the obvious and except for a handful of cases it will robably makes little harm.

rhhs · 2024-12-03T18:19:58.031Z

An example of a section I tagged as alpine hiking T4 because of “Use of hands needed in order to advance” that is without incline.

IMG_20241111_153134161_HDR1920×3412 864 KB

Did I tag that correctly?

supsup · 2024-12-03T18:35:10.629Z

I think this is ok. I would probably tend to put demanding_mountain_hiking because there is no exposure (and to anyone having sticks or even a branch, which I do not count as using hands, hands would not be necessary), but I can live with your classification too. Definitely not hiking or below!

Road_Runner · 2024-12-03T18:45:43.957Z

It’s clearly described in the wiki, that exposure is also a criteria for sac_scale. It is the combination of exposure and technical demands that make a trail “difficult”. And that is exactly what sac scale wants to describe.
2c562810b82bf648bcf7ed9afdc91e7002e8be43_2_281x500

I would rate this route as T2 or T3 at most, it’s not a route in the sense of alpine hiking. Alpine hiking requires basic climbing skills and falls can be potentially fatal, that doesn’t seem to be the case here.
EDIT: But you could make a poll?

Road_Runner · 2024-12-03T18:53:57.613Z

Why should we remove it? It is just an abbreviation, also used by a lot of renderers like Tracestack. And also the relationship to the official sac_scale is already well described in the wiki.