|Map the inside and extents of caves|
|Status:||Draft (under way)|
|Definition:||Cave extents and objects/features inside caves|
Map the approximate extents of caves and objects inside them similar to Proposed features/man_made=tunnel.
natural=cave can be an area representing the approximate extent of a cave or a linear way in cases where the exact form of the cave is not known sufficiently well to map it or a mix of both methods can be used.
Objects and ways inside caves should be tagged in a similar way as Proposed_features/Simplify_man_made=bridge_mapping#Objects_on_bridges.
The cave relation can be used to share common attributes, collect parts and relate objects which are known to belong to a particular cave but where exact connection can not be mapped.
How to map
Caves can be mapped as ways or areas depending on their shape and how much information is available.
- as area: draw the area, tag it with natural=cave
- as way: draw the way, tag it with natural=cave. For caves consisting of many linear ways it may be a good idea to add area=no to minimize the risk of confusion.
- combination of both methods, as above it may be a good idea to use area=* to minimize the risk of confusion.
natural=cave have an implicit location underground and don't need a layer tag unless they cross other underground objects.
Points and ways inside or parts of caves can have ele=* values where known.
Avoid nodes of type natural=cave as there are plenty of them in the database and widespread confusion what they mean.
Ways, objects and natural features inside the cave
Ways (such as highways, waterways) in caves:
- for linear caves add the appropriate tags to the way representing the cave, resulting for example in a way tagged with natural=cave+highway=path
- for area caves draw the way through the cave, tag it and add location=cave and the same layer (if any) as the natural=cave
Objects in caves such as POIs, benches, waste baskets:
- node type objects which are part of one of the ways of the cave or inside the cave or the outline declared by natural=cave are considered to be part of/inside the cave and inherit the layer attributes of those ways (if any) - no additional tagging is needed.
- other objects (ways or points not part of the way natural=cave) will be considered to be inside/part of the cave if
Sometimes large cave domes can have ways or other objects crossing at different levels, those should be differentiated with level=*
A relation can be used to
- group together caves consisting of more parts
- assign name and other common attributes valid for several parts of a cave
- map various features inside caves
Some mappers prefer to use cave:ref instead of a relation to group together elements of a cave.
|name||a name||Cave name|
|access||*||common access values|
|operator||operator name||who is running the cave|
|outline||zero or more||a way forming the outline of a cave section, those may be tagged with natural=cave additionally|
|linear||zero or more||a linear way representing a cave section, those may be tagged with natural=cave additionally|
|inside||zero or more||ways,POIs and other objects inside the cave. Those should be additionally tagged with location=cave and layer as described above.|
|entrance||zero or more||objects of type natural=cave_entrance|
See cave for fee, access etc.
Possibly natural=* + location=cave could be used to map the "landscape" within the cave.
Data consumers should ensure that ways tagged with location=cave or natural=cave are handled in a similar way like ways tagged with tunnel=yes.
Routers should observe that objects in caves are reachable only by ways tagged with location=cave or natural=cave.
Specialized renderers may render the natural=cave in a way similar to that of Proposed features/man_made=tunnel. For linear segments a tunnel like rendering could be adopted.
Data validators/error checkers:
- should tolerate that natural=cave may be both linear or areas
- should tolerate highways, waterways and railways with an additional natural=cave and/or location=cave
- should tolerate type=cave for relations
- should understand that both natural=cave and location=cave imply underground location
- may check for errors in use of area=*
- may warn about natural=cave nodes (many should be cave_entrance)
- may check that highways/railways are entering the cave through natural=cave_entrance or (manmade) tunnels (no such strict requirement for waterways)
- https://www.openstreetmap.org/way/163724551 cave as linear way
- https://www.openstreetmap.org/way/80297708 cave as area
- https://www.openstreetmap.org/relation/6322276 cave relation with linear and area segments
Situation before proposal
- some caves were mapped with natural=cave as way or area - https://taginfo.openstreetmap.org/tags/natural=cave
- for some caves the hiking paths and/or waterways were mapped as tunnels with or without an additional cave=yes - https://taginfo.openstreetmap.org/tags/?key=cave&value=yes
- over 20000 natural=cave_entrance, some of them probably wine cellars and similar - https://taginfo.openstreetmap.org/tags/?key=natural&value=cave_entrance
- a number of nodes of type natural=cave exist which should be probably cave_entrances in most cases