Hi Richard, The basic problem is that the wiki descriptions tend to be prescriptive (and written by people who do not map very much themselves) rather than descriptive. For this reason many (perhaps most) mappers in Great Britain tend not to place great reliance on wiki definitions. I was certainly unaware of this tag usage, although it appears to have been applied locally <http://www.openstreetmap.org/way/77921444/history>several years ago.
Whatever its faults waterway=riverbank has been the standard way to show the areal extent of canals as well as rivers by UK mappers. To date there appear to be 1674 polygons <http://overpass-turbo.eu/s/4tA> with natural=water + water=canal of which 1541 have you as their last editor <http://overpass-turbo.eu/s/4tx> . Of the latter only one seems to retain a waterway=riverbank <http://overpass-turbo.eu/s/4ty> tag. No doubt an oversight on your part. Although you may have mapped these in the first place lots of other people have looked at them and found the original tagging acceptable. I certainly did when adding detail along the eastern end of the T&M 3 years ago. So a tagging consensus arises not just through how people map things, but also through people accepting a given way of tagging and therefore *not touching* things when mapping close by. I was vaguely aware of your edits but hadn't looked at any in detail. Broadly speaking I would say adding the natural=water + water=canal is probably fine, but deleting the waterway=riverbank is not. Large scale changing of any tag on a country wide basis should always be accompanied by a message to this list (we have recently had a mass change of Marks & Spencer to Marks and Spencer, and in the past people have corrected "The Co-operative", which is what is shown on the signs to "Co-op", and so on). Mass edits tend to give a spurious sense of consensus. It's much better to get a true consensus : even if the consensus is "agree to disagree". One other point is that as a consumer of the data you may find this tag combo works particularly well for your use-case, but it is important to be aware that the same data may be being used elsewhere and changing the tags may cause other data consumers not to work anymore. Personally I'd prefer that we denoted water areas with natural=water and then waterway=riverbank could be used for linear features and it would be possible to have nice casings on water bodies in mapnik generated renderings. However this is not the case and I live with it because its only a minor annoyance. One problem I notice is that there are a small number of linear features tagged natural=water+water=canal : I can predict that someone will advocate on the wiki that this is the only correct way to tag canals. Changing how something is tagged usually requires that the new or alternative way has some compelling advantages over the old way: the designation tag for rights of way and changing from highway=ford to ford=yes are two examples I can think of, but the 'new' public transport scheme has not displaced highway=bus_stop, probably because it was more complicated and less obvious. Regards, Jerry On 6 August 2014 19:17, richard <richardw...@leiston.info> wrote: > Firstly a disclaimer, I am mostly an armchair mapper. > > I am working my way around the canals of Britain, tracing the canal banks > and > tidying up locks etc. (I have probably seen a dozen different ways that > locks > have been tagged.) > > I started off tagging the canal banks as > > waterway=canal+area=yes > > but it was pointed out to me by another mapper that this was confusing > renderers and was pointed to the Wiki entry that suggested they should be > tagged as > > natural=water+water=canal > > I therefore changed my existing tagging to reflect this and tagged my > subsequent tracing this way. I have come across a few areas that have been > traced by others (Mostly a long time ago and IMHO very poorly) that have > been > tagged as > > waterway=riverbank > > and I have changed these as I have realigned them. > > Today I have had a critical message from another mapper who said among > other > things, > > > "Wide-ranging changes to existing tagging schemes, just because you read a > Wiki page is not good enough." > > I have two problems with this sentence, > > 1/ My CHANGES have not been what I would consider wide ranging as most of > the > mapping has been done by myself therefore new not changed. > > 2/ If the reading of a Wiki page is not good enough then why bother having > a > wiki? Do we have to resort to the mailing list every time we want to tag > something? > > If there is an "accepted" way to map canals can someone point me to it? > > > -- > Richard. > > > _______________________________________________ > Talk-GB mailing list > Talk-GB@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-gb >
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