Adding chevrons to OSM maps

[mrcharly-YHT]

I've loaded your maps, Andy onto my new acquisition (etrex legen HCx). Fab maps are, too. Nice to zoom in and see the detailed contour lines.

One thing I find missing is the chevrons. Do you know if it's possible to add these to OSM?  I fancy using the etrex to start recording some routes and improving bits of OSM.

[hbunnet]

Do you mean the steep hill chevrons as used on OS 1:50,000?  There is not enough resolution in the contours avaialable to OSM for that.

[corshamjim]

I don't suppose there's anything to stop someone from adding a new tag for gradient and adding them manually, assessing the gradient using on-the-ground survey rather than deriving from the contour data.  Whether anyone would actually render them is another matter altogether though!

[hbunnet]

 This requires a huge amount of detail to render well. www.openmtbmap.org  He might be persuaded to render the chevron detail.

I think it's a bit impractical though, you would need the chevrons on both sides of many underpasses.

[mrcharly-YHT]

I don't suppose there's anything to stop someone from adding a new tag for gradient and adding them manually, assessing the gradient using on-the-ground survey rather than deriving from the contour data.  Whether anyone would actually render them is another matter altogether though!

That's the approach I was thinking of.

Why do you think it's excessive?

The maps I've downloaded from andygates include massive detail - locations of phone boxes, cafes, etc.

[corshamjim]

Why do you think it's excessive?

Assuming that question was addressed at me, I don't think it's excessive as such.  Personally I would rather such detail were added by personal survey than deriving from often imperfect external data sources.  You and I might agree on that, but unless pretty much everyone is prepared to take that work on board the map would end up with some steep gradients mapped, but most not and little prospect of the map ever becoming 'complete'.

The people who render maps would probably only choose to render the steep gradient tag if it were reasonably well adopted (I guess - I'm not someone who renders maps myself).

Doing a quick google for it, it would seem that someone has already used the tag "gradient=steep".  Only the once though.  See OpenStreetMap Tagwatch for Great_britain :: Tag:source=* Statistics and search for the word "gradient".

"incline=steep" is slightly more popular with 7 instances in Great Britain.

[fuaran]

There is a tag for incline, which is quite commonly used. Key:incline - OpenStreetMap Wiki
I don't know how hard it would to get Mkgmap to show symbols for these. You would want different symbols based on the value of the incline, the direction, and how long the way it etc.

[andygates]

The way I'd consider that would be with a new item in the points list, for incline=*, which shows a new custom icon to be drawn up in the typ-file; that icon could be the bogstandard "black wedge" GB road sign.



There's not much resolution in 16x16 for more detail. 

It would be nice to do OS-style chevrons, but icons don't draw relative to the map lines under them: they're all always the right way up.  An informative sign plonked on the point is a decent best effort, I think.

I'd love to get it at low zoom levels, too, so you could plan routes sensibly, but I've never had a ton of joy with zoom levels.  Any ideas, osm_nerds?

[frankly frankie]

Personally I would rather such detail were added by personal survey than deriving from often imperfect external data sources.  You and I might agree on that, but unless pretty much everyone is prepared to take that work on board the map would end up with some steep gradients mapped, but most not and little prospect of the map ever becoming 'complete'.

That's only the same as the present situation with roads themselves, or road names, or roundabouts, or any number of other features.  Just further down the adoption curve, is all.

[andygates]

Aye, like buildings and street numbers: the kind of detail that rezzes-in late in the edit cycle.  Such is wiki-nature.

An enterprising geo-nerd might run the streets over the DEM and calculate where they expected chevron gradients to occur.  A derived batch import wouldn't be something the OSM community could embrace -- there are too many possible wibbles -- but it might be a good seed for a working project: "We think these are steep. Are they?"

[Richard Fairhurst]

Don't forget that OS OpenData includes a good quality DEM. You could derive steep gradients from that more accurately than from SRTM (the usual worldwide DEM used by OpenCycleMap and the like), I suspect. Haven't really looked into it though.

[andygates]

I did not know that.

Mind you, I'm having trouble just burning my usual maps at the moment.  :/

[corshamjim]

Andy Allan's blog today was interesting.

Shine  » Transport Map :: GravityStorm

His philosophy - "render and they will come"

Maybe my earlier post was somewhat pessimistic.

[fuaran]

Yes, that's the best way to encourage people to map/tag a particular thing - make it show on a map, or useful in some other sort of application.
It could be worth requesting that inclines are rendered on OpenCycleMap (though I don't know how hard it is to do in Mapnik).

[Greenbank]

It would be nice to do OS-style chevrons, but icons don't draw relative to the map lines under them: they're all always the right way up.  An informative sign plonked on the point is a decent best effort, I think.

If you always have the map page on North Up then you could have a set of chevron icons in different orientations.

Would break if you have the map on track up as i'm guessing they wouldn't rotate with the map.

But given that it's vector, can't you just put a vector chevron on the road so that it always points in the right direction?

[andygates]

If you always have the map page on North Up then you could have a set of chevron icons in different orientations.

Would break if you have the map on track up as i'm guessing they wouldn't rotate with the map.

Even if I used North Up ever, it'd fail because now you have to specify not only the existence of the incline but its orientation.  There's no way to perform that logic in mkgmap for existing inclines.  And it's an ugly cludge!  Broken as specified.   

But given that it's vector, can't you just put a vector chevron on the road so that it always points in the right direction?

There is no chevron on the ground.  The point of reference for OSM is the ground truth.  It becomes silly if we start drawing markings with fake roads. 

Yes, that's the best way to encourage people to map/tag a particular thing - make it show on a map, or useful in some other sort of application.
It could be worth requesting that inclines are rendered on OpenCycleMap (though I don't know how hard it is to do in Mapnik).

Now you're talking.  OCM's useful, and steeps are things we want to know.  This sounds like exactly the way in that you'd want to encourage chevron-hunters.