Hi, Peter Miller wrote: > Ok, thanks for that Frederik. You never know who will be on a list!
Interestingly I joined this list a while ago because I had got my hands on some admin boundary data for England and wanted to know if it was any good (the answer was no). I then forgot to unsubscribe. I'm still planning to extend the Geofabrik excerpts to cover all English counties individually once I have proper data. Unfortunately simply using OSM boundaries only works for landlocked counties; the coastal ones don't seem to include the coastline, and even if they did, a "proper" coastline is not what you want to use for the excerpt, instead you want to draw a line a few kilometres out to sea where the border meets the coastline, then up/down in a straight line, and back in - which saves computing time and also ensures that any pier etc. that crosses the coastline is also included. > One limitation of OSM at present is that the category=Region_in_Engand > doesn't work if one also wants to tag the same relationship as something > else, for example as 'administrative county in England' or as > 'ceremonial county in England' or anything else. So would it be > appropriate to tag it as 'Region_in_England=yes'? Actually I assumed that any relation with boundary=administrative and a certain admin level and which lies within the England polygon would automatically be a "region in England"? Would you not be adding duplicate information by that extra "region_in_england" tag (or relation)? > What is good about relations is that a thing (way/relation) can be part > of many other things and there isn't another neat way of doing that in > OSM (other than using tag=yes where 'tag' is the category name). If you have many unrelated groups of the same type and something can be a member of any or all of them - for example cycle routes - then there's no alternative to relations. If the fact that something belongs to a group can be determined from existing tags, then a relation is not necessary. There is neither a need for a relation "footways in East Anglia" nor is there a need for "footway_in_east_anglia=yes" because the boundary of East Anglia is known and whether something is a footway is also known, thus the information is already there and should not be duplicated. This is different from cycle routes because whether or not a way is part of a cycle route cannot be seen from its existing tags (and the old route=... tag was insufficient because it only worked for zero or one route). > Should we suggest that the 'Footways in East Anglia', or more usefully > 'long distance footpaths in England' should be tagged as 'long distance > footpaths in England'=yes. No. I simply download all footpath relations, look at their length, compare it to some "long distance" threshold, and then I can give you a list of long distance footpaths. No need to tell me explicitly. What you are suggesting to do is something like the "is_in" tag, or like adding "length=1.2km" to a bit of road - you take the existing geometry and make a tag (or relation membership) from it, which thereafter has the potential to conflict with the geometry. If I remove half of the ways from a "long distance footpath", does it continue to be a "long distance footpath", or do I then need an editor that pops up an alert saying "Hey, you just shortened this and it now falls below the long distance threshold, please consider removing this from the long distance footpaths relation"? I agree this is all very much theoretical database babble but with your "regions in England", if, god forbid, I moved one of these to Spain in my editor, it would not be a "region in England" any longer, would it? Bye Frederik -- Frederik Ramm ## eMail [email protected] ## N49°00'09" E008°23'33" _______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
