[OSM-talk] area topology

[Andy Robinson (blackadder-lists)]

Jannis Achstetter wrote:
>Sent: 14 May 2008 8:05 AM
>To: talk at openstreetmap.org
>Subject: Re: [OSM-talk] area topology
>
>Stephen Gower schrieb:
>> On Tue, May 13, 2008 at 02:31:32PM +0100, Andrew Chadwick (email lists)
>wrote:
>>> I subscribe to the view that areas should correspond to the real area on
>>> the ground and mostly be kept clear of roadways. Placing an Area's Nodes
>>> near the adjacent Way's nodes helps make the map easier to maintain. I
>>> will often abut adjacent areas that are separated only by something thin
>>> and make their nodes share, however.
>>
>>   Putting the other side of the argument, as Andrew I'm sure knew I
>>   would:
>>   [...]
>
>How about buildings that really are at the edge of a road? (No fence, no
>space). I'm afraid I can't show you a photo yet.
>Do they share nodes since the "buildings are the border of the road" or
>don't they share them since "you can't enter the building from any point
>of the road"?
>(The area I talk about is this one:
>http://informationfreeway.org/?lat=49.971764870557124&lon=9.161737364989326
>&zoom=17&layers=B000F000F

In this case if highway means the whole of the roadway width including any
sidewalk/pavement if applicable (as it generally does in an OSM context) and
the house abuts the highway then the two physical objects share the same
boundary and hence can be mapped in OSM using common nodes. Where some other
physical feature exists between the two objects then they should be
separated, unless it's a regular linear feature, in which case the same
nodes can also be used for that; a fence for instance. If they are separated
by an area, grass for instance, then the highway and building ought not to
share nodes.

The fact that you cannot enter the building from the highway should be
immaterial as we only normally make common paths between common features,
although there are one or two logical exceptions to this rule. A slipway
into a body of water might be an example.

>
>and I know the buildings' shapes aren't correct but there are no
>Yahoo-Images for the city and I just did a quick run over the campus to
>get it mapped basically.)

And that is the way it should be.

>In this case I didn't share nodes to be able to edit the buildings
>without having to change the road every time (and to make the road have
>less nodes sind it really is 100% straight).

Acceptable. If someone thinks it should be done differently then they are
entitled to change to better reflect the physical.

Cheers

Andy