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#1 2017-11-20 22:37:04

SafwatHalaby
Member
Registered: 2017-04-10
Posts: 395
Website

highway=unclassified vs highway=track

I think some of our tagging conventions stray from the global conventions for no good reason

Our conventions:

  • highway=track: Any unpaved road regardless of routing importance.

  • highway=unclassified:Smaller paved roads in non-residential places. e.g. agricultural roads, forest roads, roads from behind one village to behind another village, etc.

Global conventions

  • highway=unclassified: is a bit more important in the road grid - it interconnects towns/cities/villages. It is assumed to be paved by default, but it is not necessarily so.

  • highway=track: is mostly agricultural use, forest tracks, usually unpaved but necessarily so.

Like all roads, pavement status can be explicitly indicated with the surface tag in both cases.

This difference may create practical problems:

Let me expand on my previous point with a practical example. Let's assume renderers mark "unclassified" more prominently than "track".

This unpaved road connects Daliyat el Carmel to Ein Hod. Internationally it'd be "unclassified" and would be  rendered more prominently than the surrounding tracks because it's more important in the road grid, but our guidelines make it look just like any nearby track.

Even worse, if there had been a paved but barely used forestary track nearby, our guidelines mandate tagging it as "unclassified", making it look more prominant on the map than the relatively important village-connecting road.

PS. the only reason the road looks special on Mapnik is because the forest nearby was mapped more precisely around it. The track line itself is identical to the nearby tracks

PS2. it's a non-important road in the "grand scheme of things" but it is the most important in the area when it comes to the routing grid.

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#2 2017-11-20 22:51:44

Harel M
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From: Israel
Registered: 2013-04-14
Posts: 41
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Re: highway=unclassified vs highway=track

My only question regarding your post is what about service road - is it "between" unclassified and track or above unclassified in the road grid?
I'm not sure I fully have a grasp of the difference.
In any case, I don't see a good reason to stray from the global conversions, but an effort should be made to fix this if you want to align all usages...

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#3 2017-11-21 08:24:41

zstadler
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Registered: 2012-05-05
Posts: 288
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Re: highway=unclassified vs highway=track

For decades, before OSM or the internet were created, the map conventions in Israel make a clear distinctions between a paved ("דרך סלולה") and an unpaved road ("דרך עפר"). That's a very good reason to set local guidelines.

33059349-884be362-ce9c-11e7-81b0-83eb01c93061.png

going back to the British Mandate era:

33059589-8bd4374a-ce9d-11e7-82a8-3876aadf1325.png

In fact, the general guideline for unclassified roads declared itself as secondary to country-specific and even region-specific guidelines:

Physically, the roads which should be tagged in OSM as highway=unclassified can vary greatly between countries, and even between areas in the same country. However, within the same local area, physical comparisons can be made to decide the level of importance. Use the mapping customs in your own country, together with your knowledge and judgement.

On the other hand, the "practical problem" description seems to me like a classical example of mapping for the renderer. It looks like you don't like how Mapnik is rendering the map in your vicinity.

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#4 2017-11-21 09:04:17

SafwatHalaby
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Registered: 2017-04-10
Posts: 395
Website

Re: highway=unclassified vs highway=track

Harel M wrote:

My only question regarding your post is what about service road - is it "between" unclassified and track or above unclassified in the road grid?
I'm not sure I fully have a grasp of the difference.
In any case, I don't see a good reason to stray from the global conversions, but an effort should be made to fix this if you want to align all usages...

Service roads are for.. well, providing specific services: A short road for a parking lot, house, or a fuel station entrance, a fast-food drive-through road, etc. It is less important than both track and unclassified when it comes to routing, it does not connect different places, and it's usually very short.

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#5 2017-11-21 09:25:00

SafwatHalaby
Member
Registered: 2017-04-10
Posts: 395
Website

Re: highway=unclassified vs highway=track

Hi zstadler,

Mapping for the renderer means tagging incorrectly to make things look pretty. On the other hand, I am trying to adhere to the global convention that the "highway" tag is about routing importance, and not about paving. Yes, it probably does make rendering prettier, and it probably does make routing better. Those are very good side effects.

zstadler wrote:

In fact, the general guideline for unclassified roads declared itself as secondary to country-specific and even region-specific guidelines.

To take an extreme example: You wouldn't see a country using the highway tag to indicate the lit status of roads or whether the road is a fee road or not. That place-specific leeway is not to be interpreted too liberally. The highway tag is about *road importance*, and as long as one is adhering to that, country-specific or region-specific variations are ok. But we've ditched the importance difference between "track" and "unclassified" and are tagging something else entirely.

zstadler wrote:

For decades, before OSM or the internet were created, the map conventions in Israel make a clear distinctions between a paved ("דרך סלולה") and an unpaved road ("דרך עפר"). That's a very good reason to set local guidelines.

I am pretty sure this is not Israel-specific, and that there are many worldwide non-osm maps that tag by "dirt" and "paved". I am not sure how this should affect osm tagging.

Please note that renderers probably still make a color/thickness/rendering distinction when "unclassified/track" is combined with "surface", and if they don't, then perhaps they should be fixed, not the tags (otherwise this would be mapping for the renderer). So this change proposal is not necessarily proposing to affect Israeli/IHM legends.

Edit: The issue was first mentioned here https://www.openstreetmap.org/changeset/31346575 by dsh4

Last edited by SafwatHalaby (2017-11-21 09:45:41)

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#6 2017-11-21 14:09:31

zstadler
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Registered: 2012-05-05
Posts: 288
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Re: highway=unclassified vs highway=track

It seems like this discussion is not productive.

I was quoting the wiki page for highway=unclassified, not changing the meaning of the highway tag to its lit status.

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#7 2017-11-21 15:11:32

SafwatHalaby
Member
Registered: 2017-04-10
Posts: 395
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Re: highway=unclassified vs highway=track

I am sorry if it was understood that way. Perhaps the "talking tone" is lost in messages. I am trying to make a constructive and objective point and am willing to stand corrected smile . I tried illustrating with an obviously absurd example but perhaps that made my point vague. Let us review the quote again:

Physically, the roads which should be tagged in OSM as highway=unclassified can vary greatly between countries, and even between areas in the same country. However, within the same local area, physical comparisons can be made to decide the level of importance. Use the mapping customs in your own country, together with your knowledge and judgement.

I am trying to say that the above quote above does not allow arbitrary regional guidelines. It is talking about regional differences in the definition of the "level of importance". For instance, this is why it's OK for Israel to tag primary/secondary/etc based on sign color.  Other quotes state very explicitly that track roads can be paved, and unclassified roads can be unpaved. It is also clear that the highway tag is about the level of importance, and not about other attributes such as pavements (or, more absurdly, lit status).

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#8 2017-11-22 01:11:08

dsh4
Member
Registered: 2017-06-24
Posts: 43

Re: highway=unclassified vs highway=track

zstadler wrote:

For decades, before OSM or the internet were created, the map conventions in Israel make a clear distinctions between a paved ("דרך סלולה") and an unpaved road ("דרך עפר"). That's a very good reason to set local guidelines.

Yes, it's a very good reason to set guidelines for renderers (but not for taggers).  You are welcome to propose Israeli guidelines that say that "paved roads should be rendered differently to unpaved roads".  Renderers that target Israeli users would follow those guidelines (even when generating maps of, say, Nepal targeted for Israeli users) and renderers that target other demographic groups would not (say, a map of Israel rendered for Nepali users would not follow those guidelines, but the Nepali customs).

The value of the "highway" tag reflects a road's importance in the regional roads network.  That does not change from country to country; OSM has, by design, only one data model for the whole world.  According to that data model, how roads would be rendered has nothing to do with how they should be tagged.

Your use-case would still be served: if you want a map to make a distinction between paved and unpaved roads, you should write a renderer that consults the surface=(paved|unpaved) tag when choosing how to render a road.  When the "surface" is not tagged explicitly, that is when region-to-region variation is allowed: "surface=unclassified" in England should be assumed to be paved and "surface=unclassified" in certain parts of Africa should be assumed to be unpaved.

Choosing between "track" and "unclassified" to match the rendering convention (the one in the pictures your posted, or any other) would be tagging for the renderer.

On the other hand, the "practical problem" description seems to me like a classical example of mapping for the renderer. It looks like you don't like how Mapnik is rendering the map in your vicinity.

I agree, zstadler: the problem is not that Mapnik renders highway=track as less important than highway=unclassified.

The problem is that all consumers of OSM data consider highway=track as more minor than highway=unclassified; Mapnik is simply a proxy (and a bit of a special case since it's designed with mappers as its target audience).

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#9 2017-11-22 09:05:55

SafwatHalaby
Member
Registered: 2017-04-10
Posts: 395
Website

Re: highway=unclassified vs highway=track

The value of the "highway" tag reflects a road's importance in the regional roads network.  That does not change from country to country

Agreed.

When the "surface" is not tagged explicitly, that is when region-to-region variation is allowed

Regional variation is also allowed in defining "importance"; A small, narrow, infrequently used road road could be "secondary" or "primary" in Africa if it's the best one in the area, and no better / larger / more important / more frequently used roads are available in that particular region. The same road would have been "track" or "unclassified" if it were somewhere else. Example: https://www.openstreetmap.org/way/441102489

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#10 2017-12-01 01:28:05

dsh4
Member
Registered: 2017-06-24
Posts: 43

Re: highway=unclassified vs highway=track

dsh4 wrote:
zstadler wrote:

For decades, before OSM or the internet were created, the map conventions in Israel make a clear distinctions between a paved ("דרך סלולה") and an unpaved road ("דרך עפר"). That's a very good reason to set local guidelines.

Yes, it's a very good reason to set guidelines for renderers (but not for taggers).  You are welcome to propose Israeli guidelines that say that "paved roads should be rendered differently to unpaved roads".  Renderers that target Israeli users would follow those guidelines (even when generating maps of, say, Nepal targeted for Israeli users) and renderers that target other demographic groups would not (say, a map of Israel rendered for Nepali users would not follow those guidelines, but the Nepali customs).

@zstadler I'd like to continue this discussion and hopefully reach some common ground.  Would you like to comment on my reply to your (quoted) point?  I look forward to your response.

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