OSM maps - Legends / Map Keys

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OSM maps - Legends / Map Keys

Postby peregrinator » Mon 24 Dec, 2018 3:20 pm

I've been searching for info about what the subject line describes. From the OSM Australian Wiki site https://wiki.openstreetmap.org/wiki/Category:Australia, I see that by choosing the Cycling option and then selecting Map Key, I get a contoured map with a straight-forward legend (e.g. https://www.openstreetmap.org/#map=16/-37.2846/144.2121&layers=C), which seems to broadly correspond to the way basic data is displayed in andrewp's excellent Australian OSM maps. (Unlike the wierd and wonderful legends that are on offer from the international OSM site I looked at initially, were a legend may include 88 different types of grass meadow!) There's one puzzling difference though, which I'm hoping someone can explain.

In the OSM Wiki legend above, all vehicular bush tracks are shown as brown dashed lines. For andrewp's Vic, NSW and SA maps, such tracks are shown as either brown or red dashed lines. What's intended by that distinction? I'm guessing that brown is 2WD and red is 4WD, but I'd like to be sure.

I guess also that I might as well ask one more question, given that the Map Key I mention above, being classified as Cycling, does have some data not relevant to bushwalking. Is there a way to get to a legend which is relevant?
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Re: OSM maps - Legends / Map Keys

Postby Warin » Mon 24 Dec, 2018 4:25 pm

Hi,

Pick on a track that has the red lines .. now find it on
https://www.openstreetmap.org/ - zoom in so you can use the "?" Query features thingy on the lower right side
That will bring up a list of things on the left side - you want a way usually 'track' .. click in that and you will then see the tags used on it .. surface=unpaved etc ..
Repeat for your brown lines and you should be able to determine the difference.

------------------
There is a comparison of hiking maps (OSM is not Australian so they don't use the term bushwalking)
https://wiki.openstreetmap.org/wiki/Compare_Hiking_Maps
Be aware that the end column is coverage - some 'only' do Europe.
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Re: OSM maps - Legends / Map Keys

Postby tastrax » Mon 24 Dec, 2018 5:07 pm

Ok, first up OSM is basically a big fat database with features in it and lots of 'tags'. People then use that database to create their own maps based on the tags.

Also remember that there are many instances of OSM map tiles in existence and they may all render quite differently depending on the focus of the person hosting the tiles. You can see this by switching the options and checking each map key on the main map page (as you have done). Some renders provide a legend - others dont. The legend will also change as you zoom in and out.

here are just a few of the tile servers and their different renderings - https://wiki.openstreetmap.org/wiki/Tile_servers

Andrewp doesn't have to follow anyone else's legend styles and may have created his own to better visualise features for walkers. This is the beauty of the open system, it can be tailored to specific user groups. Andrewp may be able to provide a legend for his rendering of OSM data. The more useful tags an object has the more ability a renderer has of making subtle changes to differentiate between objects.

Here is some information on how lots of Aussies tag features - https://wiki.openstreetmap.org/wiki/Aus ... Guidelines

Feel free to ask any more questions
Cheers - Phil

OSM Mapper
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Re: OSM maps - Legends / Map Keys

Postby andrewp » Thu 27 Dec, 2018 8:16 pm

As tastrax says, OSM is a database with tags. There are many contributors and people don't always use the same tagging methodology. This makes it difficult to have any consistency when producing maps from OSM.
Converting OSM tags to Garmin styles is equally complicated. The final display is determined not just by tags, but also zoom levels.
I inherited a set of styles but I'm not quite sure where from. I haven't made many changes. It is quite time consuming. Make a change, regenerate the map and have a look. The change may look better for one area, but have undesirable consequences somewhere else where the tags are different.
Basically the legend hierarchy is as follows:
Yellow solid, grey outline: secondary
Orange solid, orange outline: tertiary
White solid, grey outline: residential/service
Red dash: unclassified
Brown dash: track
Red dot: footway/path
There are tags that can be used to distinguish 4wd tracks, but IMO they are not used widely enough to be useful/reliable.
My priority was to produce maps for bushwalking. If I want to know about access road classification I would use the relevant states online mapping.

peregrinator wrote:In the OSM Wiki legend above, all vehicular bush tracks are shown as brown dashed lines. For andrewp's Vic, NSW and SA maps, such tracks are shown as either brown or red dashed lines. What's intended by that distinction? I'm guessing that brown is 2WD and red is 4WD, but I'd like to be sure.

To answer your specific question. Red dash roads are tagged as highway=unclassified and brown dash roads are tagged as highway=track. I.e red dash is more likely to be 2wd and brown dash is more likely to be 4wd. Where were you looking at when you came to the opposite conclusion?
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Re: OSM maps - Legends / Map Keys

Postby peregrinator » Fri 28 Dec, 2018 9:23 am

Thank you Warin, tastrax and andrewp for helpful information.

Andrewp: To answer your specific question. Red dash roads are tagged as highway=unclassified and brown dash roads are tagged as highway=track. I.e red dash is more likely to be 2wd and brown dash is more likely to be 4wd. Where were you looking at when you came to the opposite conclusion?

Good question but I'm not sure my answer will be useful. I looked at numerous locations, only to arrive at the conclusion that the red/brown distinction seemed somewhat random. That was particularly so when viewing alpine or lower mountain areas where there is a profusion of tracks. So in the end I could only guess. And continually change my mind the more I looked. I did have the thought that perhaps a track that is 2-WD at its beginning but deteriorated to 4-WD might be regarded as 4-WD for its entirety in order to simplfy things. Perhaps I'm wrong to make that judgement, but it does perhaps reinforce what you're saying about the potential for unreliable data.

I'm glad you mentioned using state mapping to find out about road classification. Not long ago that would be the first and only place I'd go to, but I've become too easily captured by the one-stop-shop of your maps on my computer and GPS device.
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Re: OSM maps - Legends / Map Keys

Postby neilmny » Fri 28 Dec, 2018 9:55 am

There is a lot of poorly tagged and in quite a lot of cases excessively tagged data in OSM.
I think you are right to assume that a dead end "way" tagged as a "track" near to it's origin does not become "unclassified" some distance further along into the bush.
These anomolies can be edited by anyone who has enough interest to do so.
If you have first hand knowledge of a "highway" or "way" being incorrectly tagged you can edit the "highway=" tag to what is appropriate.
That way in a couple of days the data files people download to make their maps and GPS files will have the correction included.
https://www.openstreetmap.org/#map=7/-36.209/145.701
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Re: OSM maps - Legends / Map Keys

Postby Warin » Fri 28 Dec, 2018 10:13 am

andrewp wrote: If I want to know about access road classification I would use the relevant states online mapping.


A word of caution here. The states online mapping copyright may not be compatible with OSM requirements, so it should not automatically be used to edit OSM data.

-------------------
Regarding OSM consistency .. yes well, no it is not consistent.

But then neither is state data .. roads going from Queensland to NSW can have a higher sate classification in Queensland that in NSW... There are arguments over it, probably depends on where you come from :)

And OSM is world wide .. so you have someone from Germany who has major motorways every where and then someone from Democratic Republic of Congo with major highways that are impassible in the wet as they are dirt and full of holes that swallow trucks. So the consistency is relative on a world scale. Most of us ozzies try to keep some constancy within 'our' country. One example I have left alone is in PNG, the Kokoda Trail (not Track - the PNG people call it a trail and that is its official name there) is tagged as a trail not a path .. despite there never being a vehicle over it (and there never will) for many reasons I think it will probably remain tagged as a trail in OSM.

----- Time lag from data update to map..
This will depend on the map maker. The data that you change is very quick. Propagation through to the relevant map can be hours to a year of more. E.G. changes to walking route go through to https://hiking.waymarkedtrails.org/#?ma ... 4!150.9262 within hours. The map behind those routes is nowhere near that quick. OSMAnd updates monthly .. but the update may not include things done recently .. so while you can update monthly .. I'd say it can be 2 months behind.
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Re: OSM maps - Legends / Map Keys

Postby neilmny » Fri 28 Dec, 2018 11:01 am

This data is updated every 24 hours. http://download.geofabrik.de/australia- ... ralia.html
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