[talk-ph] to share or not to share nodes?

[maning sambale]

Hi,

I'm posting this inquiry to gather best practices when editing nodes
and ways.  Basically, OSM data are composed of two data primitives:
nodes (points, vertices) and ways (lines and polygons).  Relations are
special type of ways and nodes.  The data model allows for sharing
nodes/ways with different tags.  For example, a node can be part of a
highway, traffic_signals can be added to node which is part of a
highway way.

However, in many cases it is good editing practice to minimize node
sharing.  Partly for ease of editing and partly to avoid routing
errors (especially for highway ways).  Here's a list of editing
practices I will use from hereon in order to avoid node sharing
problems mentioned above.  Please add or delete anything in the list.

1. Highways should not share nodes with other non-highway related ways
(such as administrative boundaries, landuse, building outlines)
2. Nodes for adjacent landuse types can share nodes.
3. Administrative boundaries should be in relations not as shared nodes/ways.
4. Natural and landuse ways can share nodes.  For example,
natural=water (for lakes) can share nodes with landuse=farm.
5.  Admin boundaries should not share nodes with landuse.  Landuse
change more often than admin boundaries.
6.  add more here ...


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maning
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Re: [talk-ph] to share or not to share nodes?

[Jim Morgan]

maning sambale wrote, On Tuesday, 27 April, 2010 05:33 PM:
> However, in many cases it is good editing practice to minimize node
> sharing.  

> 4. Natural and landuse ways can share nodes.  For example,
> natural=water (for lakes) can share nodes with landuse=farm.

I'm never quite sure how I should be doing beaches [being a bit of an 
accidental island specialist .. :-)]

It seems fairly logical to join the seaward edge of the beach to the coastline. 
Is that OK? Does it play well with the 'shapefiles' whatever they might be ...

On the other hand I have some misgivings about it, because its a hassle to 
un-glue the beach edge and the coastline when you need to edit/move the beach. 

Hmmm. 

Jim

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Re: [talk-ph] to share or not to share nodes?

[Eugene Alvin Villar]

Personally, I am more bothered with overlapping ways than with shared nodes.

Nodes should be shared if the two ways sharing that node have an intrinsic
positional relationship on that node. If you use two different nodes with
the same coordinates, then you risk having the duplicated node problem.

As for admin boundaries sharing nodes, sometimes that is the only clean way
to signify the relationship of an admin boundary with surrounding landuses.
Case in point is the eastern boundary of Barangay Ayala Alabang in
Muntinlupa . This border is exactly the
eastern perimeter of Ayala Alabang Village. The landuse covering Ayala
Alabang Village shares almost all of its nodes with the ways that make up
Brgy. Ayala Alabang. I actually am thinking of breaking up the Ayala Alabang
Village landuse polygon into parts, delete the redundant ways and create a
multipolygon relation reusing the admin boundary ways so that there are no
more overlapping ways.


On Tue, Apr 27, 2010 at 5:33 PM, maning sambale
wrote:

> Hi,
>
> I'm posting this inquiry to gather best practices when editing nodes
> and ways.  Basically, OSM data are composed of two data primitives:
> nodes (points, vertices) and ways (lines and polygons).  Relations are
> special type of ways and nodes.  The data model allows for sharing
> nodes/ways with different tags.  For example, a node can be part of a
> highway, traffic_signals can be added to node which is part of a
> highway way.
>
> However, in many cases it is good editing practice to minimize node
> sharing.  Partly for ease of editing and partly to avoid routing
> errors (especially for highway ways).  Here's a list of editing
> practices I will use from hereon in order to avoid node sharing
> problems mentioned above.  Please add or delete anything in the list.
>
> 1. Highways should not share nodes with other non-highway related ways
> (such as administrative boundaries, landuse, building outlines)
> 2. Nodes for adjacent landuse types can share nodes.
> 3. Administrative boundaries should be in relations not as shared
> nodes/ways.
> 4. Natural and landuse ways can share nodes.  For example,
> natural=water (for lakes) can share nodes with landuse=farm.
> 5.  Admin boundaries should not share nodes with landuse.  Landuse
> change more often than admin boundaries.
> 6.  add more here ...
>
>
> --
> cheers,
> maning
> --
> "Freedom is still the most radical idea of all" -N.Branden
> wiki: http://esambale.wikispaces.com/
> blog: http://epsg4253.wordpress.com/
> --
>
> ___
> talk-ph mailing list
> talk-ph@openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk-ph
>



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Re: [talk-ph] to share or not to share nodes?

[maning sambale]

On Tue, Apr 27, 2010 at 7:18 PM, Jim Morgan  wrote:
> On the other hand I have some misgivings about it, because its a hassle to 
> un-glue the beach edge and the coastline when you need to edit/move the beach.
When you move the beach it makes sense that coastlines move as well.
Anyone knows how to unglue ways in Potlatch?


-- 
cheers,
maning
--
"Freedom is still the most radical idea of all" -N.Branden
wiki: http://esambale.wikispaces.com/
blog: http://epsg4253.wordpress.com/
--

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