On Sep 21, 2014, at 7:34 AM, Pee Wee wrote:

> Well if an unpaved  forest path would get gravel or fine_gravel thrown on top 
> of it I would consider this some sort of paving that could be classified as 
> "paved". You apparently don't. No need to argue about that , it only goes to 
> show that the suggested tag would not work. ;-)

In my part of the world, I can't imagine anyone in the general public 
considering a gravel surfaced path or road as being "paved".

On Sep 21, 2014, at 12:29 AM, Pee Wee wrote:

> -1
> A renderer/router is perfectly capable of deciding what he thinks is 
> paved/unpaved. He can decide whether he calls gravel / fine_gravel paved or 
> unpaved. Do not leave the decision paved/unpaved  up to the mapper. Map what 
> you see. As you may have guessed I prefer surface=asphalt over surface=paved 
> since the last one could mean that it is gravel.

In my mind, a good tagging scheme should have two main goals:
1. To be easy for a novice or entry level OpenStreetLevel mapper to do.
2. Be easy for data consumers to digest for wide spread uses.

Looking at the first, in many cases we fail miserably at this. Where to go for 
definitive information (wiki, taginfo, mail lists, which of a couple help 
forums, etc.)? But we also fail when we try to get too sophisticated with our 
tagging. Despite being actively discouraged, "paved=yes/no" is used. And two of 
the top values for "surface=*" are "paved" and "unpaved", clearly taggers find 
the concept of "is paved" versus "is not paved" a natural one. And I strongly 
suspect you would get a more consistent result from an arbitrary person trying 
to "map what you see" if you asked them to look at a road and determine if it 
was paved or not than if you asked them to specify the name of the surface 
material. This is particularly true if their survey consists in driving from 
point A to point B and then asked (or trying to edit data in OSM) what the road 
surface was on each section road they used. They can probably tell you which 
sections were "unpaved" and which were "paved" but not tell you where the 
surface changed from concrete to asphalt, etc.

On the second point, looking on printed maps of many vintages and at several 
routing engines, I see a distinction between "paved" and "unpaved". But not, 
with the exception of maps for a pretty specialized small group of people like 
highway engineers, between various paving types. So I think the biggest use of 
the "surface=*" tag is to determine "paved=yes/no". Giving a multivalued field 
to data consumers that need a boolean value requires a translation of some 
sort. We should not be "(mis)tagging for the (broken) renderer", but 
fundamentally we are "tagging for easy use by a software based data consumer" 
and in many years of software engineering I've noticed that every time you 
build a need for a translation in a process you build in a place for an error 
to creep in. So while "a renderer/router is perfectly capable of deciding" 
there can be inconsistencies in that translation between one data consumer and 
another leading people to suspect that something is flawed in data source.

From both of the above, it seems that having "paved=yes/no" with "surface=*" 
would make it easier for both OSM mappers and OSM data consumers.


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