[OSM-talk] Layers and landuse

[Ture Pålsson]

I recently taught my rendering hack about the ’layer’ tag, and immediately 
encountered a set of new problems. For example, consider this ditch: 
http://www.openstreetmap.org/way/243331898 
 . It has layer=-1, probably to 
indicate that is passes under the road which it crosses. However, it is 
entirely covered by a landuse=farmland with no layer tag, which I take to mean 
an implicit layer=0. This means that my renderer now renders the farmland over 
the ditch, completely hiding the latter. Meanwhile, Mapnik obviously does what 
the tagger intended.

Is this a tagging error, that I should fix by editing the data, or is it 
something that my renderer should be able to cope with?

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Re: [OSM-talk] Layers and landuse

[michael spreng]

On 27/06/15 10:40, Ture Pålsson wrote:
> I recently taught my rendering hack about the ’layer’ tag, and
> immediately encountered a set of new problems. For example, consider
> this ditch: http://www.openstreetmap.org/way/243331898 . It has
> layer=-1, probably to indicate that is passes under the road which it
> crosses. However, it is entirely covered by a landuse=farmland with no
> layer tag, which I take to mean an implicit layer=0. This means that
> my renderer now renders the farmland over the ditch, completely hiding
> the latter. Meanwhile, Mapnik obviously does what the tagger intended.
>
> Is this a tagging error, that I should fix by editing the data, or is
> it something that my renderer should be able to cope with?
>
This is not a tagging error. You should have different sets of layers
for different things. Usually areas are in a lower set of layers than
lines, meaning that all areas are rendered below lines. This makes
tunnels visible below a forest and similar things. And also your example
is covered by this.

Michael
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Re: [OSM-talk] Layers and landuse

[Tobias Knerr]

On 27.06.2015 11:19, michael spreng wrote:
> This is not a tagging error.

It is an error. Only the underground part of the ditch should have
layer=-1, and it needs to also have a tunnel tag.

As for landuse, such areas are typically non-physical, and as such not
easily inserted into the layer hierarchy. However, mappers are using
landuse far beyond its original definition, and also map physical things
such as pastures and (arguably) fields with it. At that point, the usual
layer rules need to apply.


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Re: [OSM-talk] Layers and landuse

[Martin Koppenhoefer]

2015-06-28 14:39 GMT+02:00 Tobias Knerr :

> On 27.06.2015 11:19, michael spreng wrote:
> > This is not a tagging error.
>
> It is an error. Only the underground part of the ditch should have
> layer=-1, and it needs to also have a tunnel tag.
>
> As for landuse, such areas are typically non-physical, and as such not
> easily inserted into the layer hierarchy. However, mappers are using
> landuse far beyond its original definition, and also map physical things
> such as pastures and (arguably) fields with it. At that point, the usual
> layer rules need to apply.
>
>

completely agree. I had written something similar, but accidentally the
mail was only sent to Michael and not to this list...

Cheers,
Martin
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Re: [OSM-talk] Layers and landuse

[Warin]

On 29/06/2015 1:14 AM, Martin Koppenhoefer wrote:



2015-06-28 14:39 GMT+02:00 Tobias Knerr >:


On 27.06.2015 11 :19, michael spreng wrote:
> This is not a tagging error.

It is an error. Only the underground part of the ditch should have
layer=-1, and it needs to also have a tunnel tag.

As for landuse, such areas are typically non-physical, and as such not
easily inserted into the layer hierarchy. However, mappers are using
landuse far beyond its original definition, and also map physical
things
such as pastures and (arguably) fields with it. At that point, the
usual
layer rules need to apply.



completely agree. I had written something similar, but accidentally 
the mail was only sent to Michael and not to this list...





My take...

If lower than the 'original ground level' then layer=-1 (or more)

If the 'ditch' is covered then it is a tunnel or a culvert, if there is 
no 'roof' then it is a cutting.
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Re: [OSM-talk] Layers and landuse

[Martin Koppenhoefer]

sent from a phone

> Am 29.06.2015 um 00:42 schrieb Warin <61sundow...@gmail.com>:
> 
> If lower than the 'original ground level' then layer=-1 (or more)


"layer" are tags to map relative local stacking (which object is above which 
other object where they overlap), it has nothing to do with original ground 
level. Where objects do not overlap, the tag is meaningless.


cheers 
Martin 
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Re: [OSM-talk] Layers and landuse

[Warin]

On 29/06/2015 9:34 AM, Martin Koppenhoefer wrote:


sent from a phone


Am 29.06.2015 um 00:42 schrieb Warin <61sundow...@gmail.com>:

If lower than the 'original ground level' then layer=-1 (or more)


"layer" are tags to map relative local stacking (which object is above which 
other object where they overlap), it has nothing to do with original ground level. Where 
objects do not overlap, the tag is meaningless.



There should be a reference point, so that what one mapper maps can be verified 
by another mapper.

I use the 'original ground level' as that reference point and call it level 0.

If you used level 2 it would work ... but the next mapper could use level -2 .. 
and it would look rather strange .. especially if the two were linked .. the 
link would need to go from one level to the other.. other wise the link would 
not be to teh correct layer/level. If both mappers use the same reference 
problems are reduced.


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Re: [OSM-talk] Layers and landuse

[Lester Caine]

On 29/06/15 04:06, Warin wrote:
>>> If lower than the 'original ground level' then layer=-1 (or more)
>>
>> "layer" are tags to map relative local stacking (which object is above
>> which other object where they overlap), it has nothing to do with
>> original ground level. Where objects do not overlap, the tag is
>> meaningless.
>>
>>
> There should be a reference point, so that what one mapper maps can be
> verified by another mapper.
> 
> I use the 'original ground level' as that reference point and call it
> level 0.
> 
> If you used level 2 it would work ... but the next mapper could use
> level -2 .. and it would look rather strange .. especially if the two
> were linked .. the link would need to go from one level to the other..
> other wise the link would not be to teh correct layer/level. If both
> mappers use the same reference problems are reduced.

The problem with all of these is simply that OSM does not do height
which is a pity. I have several areas around here which are difficult to
map, and certainly can't be navigated too by a router simply because
'original ground level' is a couple of hundred feet difference from one
side to the other.

Example ... one enters the car park at level 1 ... it goes up in half
level steps to level 6 which is 'ground level' for the rest of Evesham.

Mellieha in Malta was even worse with entrances to car parks several
hundred feet above almost adjacent roads.

Landuse should be a 'virtual' layer, as should all 'political' concepts.
Keep 'layers' to at least keep the vertical structures sort of working
although it is now time that 'height' at least had some place!

What is the main problem here is the attempt to use the same way for
several unrelated elements. We know that the editors simply can't cope
with 'relations' and without a mechanism to provide duplicate ways where
one use needs splitting from another we are not going to be able to keep
the data consistent. Coastline is a goo example. If that was a set of
data on it's own 'PLANE' that could be viewed in isolation, then we
could modify the coastline and then simply flag what adjacent detail
then needs review ... coastal erosion etc.

Boundaries and landuse are another 'plane' independent of layer,
although 'mixed' use land may well be augmented by different tags once
the layers are better structured?

-- 
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-
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Re: [OSM-talk] Layers and landuse

[Richard Z.]

On Mon, Jun 29, 2015 at 01:06:18PM +1000, Warin wrote:
> On 29/06/2015 9:34 AM, Martin Koppenhoefer wrote:
> >
> >sent from a phone
> >
> >>Am 29.06.2015 um 00:42 schrieb Warin <61sundow...@gmail.com>:
> >>
> >>If lower than the 'original ground level' then layer=-1 (or more)
> >
> >"layer" are tags to map relative local stacking (which object is above which 
> >other object where they overlap), it has nothing to do with original ground 
> >level. Where objects do not overlap, the tag is meaningless.
> >
> >
> There should be a reference point, so that what one mapper maps can be 
> verified by another mapper.

this might look easy for simple crossings but in complex cases having layer=0
defined as ground level only complicates things.
People interpreting additional meanings into the layer tag causes more harm 
than good.


Richard

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Re: [OSM-talk] Layers and landuse

[Richard Z.]

On Sat, Jun 27, 2015 at 10:40:52AM +0200, Ture Pålsson wrote:
> I recently taught my rendering hack about the ’layer’ tag, and immediately 
> encountered a set of new problems. For example, consider this ditch: 
> http://www.openstreetmap.org/way/243331898 
>  . It has layer=-1, probably to 
> indicate that is passes under the road which it crosses. However, it is 
> entirely covered by a landuse=farmland with no layer tag, which I take to 
> mean an implicit layer=0. This means that my renderer now renders the 
> farmland over the ditch, completely hiding the latter. Meanwhile, Mapnik 
> obviously does what the tagger intended.
> 
> Is this a tagging error, that I should fix by editing the data, or is it 
> something that my renderer should be able to cope with?
> 

it is an error and your renderer should be able to cope with it as it is
a pretty common error.

Simply ignore any layer tags which are not in combination with 
bridge,tunnel,covered,
steps,indoor or similar - the key:layer wikipage has a longer list of 
combinations 
that seem legit.


Richard


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Re: [OSM-talk] Layers and landuse

[Florian Lohoff]

On Sun, Jun 28, 2015 at 02:39:14PM +0200, Tobias Knerr wrote:
> On 27.06.2015 11:19, michael spreng wrote:
> > This is not a tagging error.
> 
> It is an error. Only the underground part of the ditch should have
> layer=-1, and it needs to also have a tunnel tag.
> 
> As for landuse, such areas are typically non-physical, and as such not
> easily inserted into the layer hierarchy. However, mappers are using
> landuse far beyond its original definition, and also map physical things
> such as pastures and (arguably) fields with it. At that point, the usual
> layer rules need to apply.

If neighbouring fields are farmland and meadow you need to split them.
And as we all think about mapping roads as areas e.g. landuse=highway
landuses have most likely to stop at roadsides.

I consider layer=* on landuse as beeing broken. If you need to cut out
a part of an landuse thats what a multipolygon is for. For me
landuses may not overlap.

Flo
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Re: [OSM-talk] Layers and landuse

[Lester Caine]

On 29/06/15 10:59, Florian Lohoff wrote:
> I consider layer=* on landuse as beeing broken. If you need to cut out
> a part of an landuse thats what a multipolygon is for. For me
> landuses may not overlap.

As a goal for the future, a 'plane' of data that has a single landuse
classification for every point would be nice. Other projects are working
on that data and just using OSM as a background overlay. but for now, a
large residential area with a few small pockets of other areas of
activity such as a playground don't need the full multi-polygon
treatment. But should the residential road network be inside or outside
that polygon? We had the same discussion in relation to
'landuse=university' where the campus area needs an outline, but t5ere
are a lot of different 'landuse' activities within that ...

-- 
Lester Caine - G8HFL
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Re: [OSM-talk] Layers and landuse

[Martin Koppenhoefer]

sent from a phone

> Am 29.06.2015 um 09:45 schrieb Lester Caine :
> 
> Landuse should be a 'virtual' layer, as should all 'political' concepts.


+1, it already is like this 


> Keep 'layers' to at least keep the vertical structures sort of working
> although it is now time that 'height' at least had some place!


you can use ele and height tags for 3D, but either you have a very good 
imagination or you would want editor support for it.

(we could even have curves or other parametric geometry by adding curve tension 
tags to the ways or inventing freaky 3D relations (e.g. lathe, sweep)), but all 
these would need support to be useful.

The step from 2D to 3D would add a lot of complexity on the mappers, narrowing 
down the mass of contributors potentially willing and able to participate. 
Everyone would have to deal with this: It's difficult to imagine introducing 3D 
in parallel (as long as you don't do it completely disconnected, i.e. a fork), 
because everything is connected and someone not aware of 3D information would 
damage it inadvertently as soon as he was starting to make 2D edits on 3D data.

cheers 
Martin
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Re: [OSM-talk] Layers and landuse

[Martin Koppenhoefer]

sent from a phone

> Am 29.06.2015 um 09:45 schrieb Lester Caine :
> 
> Boundaries and landuse are another 'plane' independent of layer,
> 



rather than 'plane' you can see them as "pointy volumes" you get by slicing a 
piece of the globe, connecting the centre of the earth with the nodes and 
cutting along the way ;-)

cheers 
Martin
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Re: [OSM-talk] Layers and landuse

[Lester Caine]

On 29/06/15 15:08, Martin Koppenhoefer wrote:
> The step from 2D to 3D would add a lot of complexity on the mappers, 
> narrowing down the mass of contributors potentially willing and able to 
> participate. Everyone would have to deal with this: It's difficult to imagine 
> introducing 3D in parallel (as long as you don't do it completely 
> disconnected, i.e. a fork), because everything is connected and someone not 
> aware of 3D information would damage it inadvertently as soon as he was 
> starting to make 2D edits on 3D data.

I'm not so bothered about 3D, but rather making it a little clearer on
2D maps that one HAS to go a particular way when the road other side of
the building IS 5 stories below, and the main road is three stories
below that. People who have visited Malta will know what I am saying,
but following a satnav somewhere you don't know after a long flight ...
it would be nice if the map warned you :)

-- 
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Re: [OSM-talk] Layers and landuse

[Florian Lohoff]

On Mon, Jun 29, 2015 at 11:49:21AM +0100, Lester Caine wrote:
> On 29/06/15 10:59, Florian Lohoff wrote:
> > I consider layer=* on landuse as beeing broken. If you need to cut out
> > a part of an landuse thats what a multipolygon is for. For me
> > landuses may not overlap.
> 
> As a goal for the future, a 'plane' of data that has a single landuse
> classification for every point would be nice. Other projects are working
> on that data and just using OSM as a background overlay. but for now, a
> large residential area with a few small pockets of other areas of
> activity such as a playground don't need the full multi-polygon
> treatment. But should the residential road network be inside or outside
> that polygon? We had the same discussion in relation to
> 'landuse=university' where the campus area needs an outline, but t5ere
> are a lot of different 'landuse' activities within that ...

playground != landuse - leisure=playground is part of a 
landuse=residential imho. 

I'd put a area landuse=residential area amenity=school name=University ... on
that area. 

I see a huge problem coming with maintenance of the map where people
have glued together all different types of object. 
The most problematic i see here is landuse (or other area based objects
like amenity, leisure etc) and highway. As highway does
not have a dimension the landuse reusing the highway nodes means
covering half of the street. E.g. for me landuse=forest sharing 
nodes with the street means that there are trees on one side of the
road until the center line.

In some areas i have given up fixing that or even touching the map.
Whatever object you try to fix/move you end up fixing 20 objects in
the surrounding.

Flo
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Re: [OSM-talk] Layers and landuse

[Nicholas G Lawrence]

-Original Message-
From: Florian Lohoff [mailto:f...@zz.de] 
Sent: Tuesday, 30 June 2015 3:52 AM
To: Lester Caine
Cc: talk@openstreetmap.org
Subject: Re: [OSM-talk] Layers and landuse

On Mon, Jun 29, 2015 at 11:49:21AM +0100, Lester Caine wrote:
> On 29/06/15 10:59, Florian Lohoff wrote:
> > I consider layer=* on landuse as beeing broken. If you need to cut 
> > out a part of an landuse thats what a multipolygon is for. For me 
> > landuses may not overlap.
> 
> As a goal for the future, a 'plane' of data that has a single landuse 
> classification for every point would be nice.

This would be useful for the sea / land / coastline issues...

Nick



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Re: [OSM-talk] Layers and landuse

[Martin Koppenhoefer]

sent from a phone

> Am 29.06.2015 um 19:52 schrieb Florian Lohoff :
> 
> playground != landuse - leisure=playground is part of a 
> landuse=residential imho. 


could be seen like this for a subset of playgrounds (those close to 
residences), but they also occur far away from residential areas (eg in 
commercial areas, in the forest, associated to a restaurant, swimming pool or 
beach, )

I would not include them in any common landuse (that we use in osm), no need to 
put explicit landuse objects on every square millimeter, a hospital, 
playground, school or church already implicitly define the landuse



> 
> I'd put a area landuse=residential area amenity=school name=University ... on
> that area


-1


> 
> I see a huge problem coming with maintenance of the map where people
> have glued together all different types of object. 


+1, especially the glueing of objects in incompatible models (highway centre 
lines and common areas) is a preliminary sin that hopefully will vanish sooner 
or later (probably when area:highway becomes more popular)


> The most problematic i see here is landuse (or other area based objects
> like amenity, leisure etc) and highway. As highway does
> not have a dimension the landuse reusing the highway nodes means
> covering half of the street. E.g. for me landuse=forest sharing 
> nodes with the street means that there are trees on one side of the
> road until the center line.


+1


cheers 
Martin 
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Re: [OSM-talk] Layers and landuse

[Richard Z.]

On Mon, Jun 29, 2015 at 04:14:07PM +0100, Lester Caine wrote:
> On 29/06/15 15:08, Martin Koppenhoefer wrote:
> > The step from 2D to 3D would add a lot of complexity on the mappers, 
> > narrowing down the mass of contributors potentially willing and able to 
> > participate. Everyone would have to deal with this: It's difficult to 
> > imagine introducing 3D in parallel (as long as you don't do it completely 
> > disconnected, i.e. a fork), because everything is connected and someone not 
> > aware of 3D information would damage it inadvertently as soon as he was 
> > starting to make 2D edits on 3D data.
> 
> I'm not so bothered about 3D, but rather making it a little clearer on
> 2D maps that one HAS to go a particular way when the road other side of
> the building IS 5 stories below, and the main road is three stories
> below that. People who have visited Malta will know what I am saying,
> but following a satnav somewhere you don't know after a long flight ...
> it would be nice if the map warned you :)

In some cases you could use embankment, natural=cliff or building=wall 
separating
the road and the building would that work here?

Richard


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Re: [OSM-talk] Layers and landuse

[Lester Caine]

On 30/06/15 11:36, Richard Z. wrote:
> On Mon, Jun 29, 2015 at 04:14:07PM +0100, Lester Caine wrote:
>> On 29/06/15 15:08, Martin Koppenhoefer wrote:
>>> The step from 2D to 3D would add a lot of complexity on the mappers, 
>>> narrowing down the mass of contributors potentially willing and able to 
>>> participate. Everyone would have to deal with this: It's difficult to 
>>> imagine introducing 3D in parallel (as long as you don't do it completely 
>>> disconnected, i.e. a fork), because everything is connected and someone not 
>>> aware of 3D information would damage it inadvertently as soon as he was 
>>> starting to make 2D edits on 3D data.
>>
>> I'm not so bothered about 3D, but rather making it a little clearer on
>> 2D maps that one HAS to go a particular way when the road other side of
>> the building IS 5 stories below, and the main road is three stories
>> below that. People who have visited Malta will know what I am saying,
>> but following a satnav somewhere you don't know after a long flight ...
>> it would be nice if the map warned you :)
> 
> In some cases you could use embankment, natural=cliff or building=wall 
> separating
> the road and the building would that work here?

http://www.openstreetmap.org/#map=18/35.95833/14.36246 was where I had
the fun at Christmas. Vertically this area is well over 10 stories high
which the steps only hint at. We stayed at the Pergola Club Hotel and
the osmand took me to the bottom of the Trig Adenau steps while the
entrance to the car park was 5 stories above :) Other parts of Malta
were just as much fun ... and while around here is not quite so steep,
there are a number of places with similar problems when trying to work
out just where to drive.

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