Here’s a situation: an orienteering sports club wants to put all its own vector maps into OSM. The maps have to be updated before every competitions (usually every area is used for races once a year).
What can the authors do if, lets say, someone in OSM tried to “improve” data and moved paths and a lot of other stuff in a wrong place, or re-tagged everything in a wrong way, or who knows what. The edits have been overwritten by other edits since, and AFAIU, can’t be reverted. We have a local copy of the data before it was broken. Is there an easy way to merge the old version of the map with the correct edits and merge this back into OSM, like in distrtibuted version control systems?
Since it sounds like some orienteering map data may not physically exist on the ground, it is best to maintain this as a separate map layer on top of OSM data. This can be done with OpenLayers. That also ensures that the official club data is never modified by anyone else.
What do you mean by “may not physically exist on the ground”? If it’s for competitions held on the ground, and is updated every year on the ground, how can the data not be on the ground?
Let me explain it another way: I search a way to let them contribute to OSM, get some updates, but be able to exclude and fix wrong updates both in their map data and OSM. So in the end there should be actual and correct vector maps, that can be rendered with orienteering software, like Ocad.
By “may not physically exist on the ground”, I mean that it appears that there are some types of orienteering that follow a vector across an field or forest without a path. For those cases, the vector is not verifiable by someone else who is at the site on the ground. It is not customary to enter imaginary data into OSM (except for administrative boundaries).
It is not possible to exclude wrong updates. The only possibility is to monitor the area closely with the “History tab” or ITO world http://www.itoworld.com/ and make corrections to any other updates which have modified the official data.
Orienteering maps don’t show these paths; participants determine them based on the map and then use a compass to walk in that direction. Orienteering maps only show what’s on the ground, with the caveat that the stations where you punch your card are only on the ground for the event (and thus those would not be in OSM).