I came across an instance of the importance key on the node marking the summit of Ben Nevis, and was interested to see how it is used. The wiki description suggested it might be in use to classify peaks, but both taginfo’s combinations and Overpass queries in various European regions suggest it might be mainly used for railway infrastructure.
I’ve added a line to the wiki page, but the documentation could do with further updating.
Also a plea for data consumers to add their tag usage to taginfo, as this really helps in clarifying likely current uses of a key or tag.
That’s a pretty sparse wiki. I know (having written LOTS of wiki myself) that they do have to “start somewhere,” but still, that’s pretty sparse!
Also, it is worth mentioning that our wiki simultaneously can be various combinations of prescriptive (you should tag like this) as well as descriptive (in our map, tagging is found like this). It isn’t clear which wiki are which, and that can be frustrating.
And I offer huge thanks to those who use combinations of map data analysis, perusing vast distances across our wiki-universe, tools like taginfo (and others) and “clean this up.” It’s a big task, it can be quite perplexing what is the right thing to do much of the time and only as we as a community help each other improve our wiki and tagging (and tagging and wiki…) will the situation improve. It is getting better!
As term, sounds exactly subjective as woodpeck suggested, and pretty generic. Importance in what context?
I don’t find the importance key important (pun not intended). Its proposal was in 2009 for, I assume, the usage of renders. And the proposal status is Abandoned (inactive).
Even for the apparent current usage in railway infrastructure, the closest similar key would be usage and then service (in my opinion).
I wondered about that, but there are other cases which use a similar hierarchy, although for cycle routes I presume they can be discriminated on the ground.
Quite different, in that prominence is objective albeit not necessarily easy to determine. Prominence is to be preferred, but has it’s own problems: usual sources used national topo maps; not clear that it is verifiable etc.
I am not contradicting myself as I say this: even with sparse wiki I am amazed that I see 98%, 99%. often 100% effectively correct, effectively complete, what seems to be wide community-agreement.
Sometimes we take a lot of words to do that (sometimes it really does take a lot), sometimes we’re “pretty sparse.” OSM can be amazing, like “just the right amount of spice in that particular dish.”