OpenStreetMap
Improving the OSM map - Why don't we? [4]
Posted by marczoutendijk on 22 May 2015 in English. Last updated on 23 April 2017.Bits and Pieces
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In this screenshot we see redundant information. Either use building=entrance (although that is now deprecated), or use entrance=yes (or main). Don’t use both.
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What is this mapper trying to tell us? What should be fixed?
Here we see the situation:
I don’t know what to fix! -
The number of levels of the building is an estimate. But what about the colour? You cannot reliable describe the colour of a building with RGB colours! Every colour that is painted or printed is CMYK.
Discussion
Comment from Chrysopras on 24 May 2015 at 20:06
“Every colour that is painted or printed is CMYK.”
Hm, well, this is not true. In printed books, newspapers, etc., most colours are printed with CMYK colours (however, in high-quality priniting, there can be spot colours, so even for printing the CMYK rule is not always true). But the colours (tints) used for painting the walls of buildings are completely different, they can be mixed from many available colours and can cover much more of the RGB colour room than CMYK colours in printing.
Comment from Vincent de Phily on 25 May 2015 at 09:33
In the particular case of “building=entrance” I agree that it should be deleted nowadays, but don’t treat “tag redundancy is bad” as an absolute rule.
Using redundant tagging schemes can be advisable when neither scheme has fully “won” yet. Even when one has, keeping the old tag during a “transition period” makes life easyer for consumers.
Concerning colors, the RGB/CMYK conversion is the least of our accuracy worries. There are lots of physical factors that bring much bigger errors than that. The geometry isn’t centimeter-accurate either, so the color accuracy isn’t a problem. 3-bytes RGB is the color scheme that most people know about, so go ahead and always use that in OSM.