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Hi, often time when I am mapping, I find very well mapped areas however the features are all glued together. When I was learning to map, I was told that even if two separate buildings are adjacent, there should be a minimal gap so that they are not glued together. So my question is, if I find glued features, should I unglue them and make them separate? |
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The general rule is a simple one: if these objects share a boundary on the ground then their polygons should share nodes. So detached buildings should not share nodes, buildings which share walls should. Similarly with woods and lakes etc. Undoubtedly some editing actions are harder when nodes are shared, but others are easier, and furthermore useful relationships (building a touches building b) are retained. 4
I would leave buildings and other features that are glued together sharing common nodes, if this is how they are on the ground. Otherwise if one feature is moved it could encroach on the other feature, or gaps would form between them, and the map would become inaccurate. Building walls and fences are often boundary features, so the edges of two buildings will touch or even be a shared common wall. It is more accurate to glue such buildings and features together. However, separate buildings that have a clear gap, such as a narrow service way that allows somebody to access the exterior walls should not be glued together.
(24 Apr '17, 02:04)
Huttite
I understand the point however, I read in one of the tasking manager instructions that even if the buildings are together, they should not share nodes, that they should be separate. Following that rule, I always kept features separate from each other even when I knew they shared nodes. I kept a minimum gap between them but kept them separate.
(24 Apr '17, 05:23)
mmahmud
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I would be looking for the reason why that instruction was given for not sharing nodes. You may find the map easier to maintain if you follow such guidelines. But I wouldn't go around ungluing buildings because of the guideline alone. If you did need to modify or maintain an area and the glued buildings or other features stopped you doing so, say, because you could not select the particular way. Only then would I consider ungluing the various features. Otherwise I would leave things alone.
(24 Apr '17, 05:44)
Huttite
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I'm aware you're asking specifically about buildings, but for clarity I'd like to add that features such as fields, woods shouldn't be joined to roads. The ways in OSM represent the infinitesimally thin road centre line with no width implied. These features should be set back from the road using aerial imagery for guidance, if available. Example of the problem: If a farmer's field is glued to the road & a gate is then added to its boundary, it's implied the gate is also a barrier on the road. |
have a look at the list https://help.openstreetmap.org/tags/shared/?sort=mostvoted - do you find a similar or same question?
Thank you for that however, what I am looking for is, whether buildings should share nodes or buildings and areas should share nodes. I have found a lot of areas where buildings and areas share nodes.