[Tagging] surface=gravel problems

[Bert -Araali- Van Opstal]

It depends. If you would like to define gravel or any variant in the 
surface tag what exactly are we referring to ?  If a road shows not 
embedded gravel in the top surface, so a part of the gravel can clearly 
be observed as "loose" gravel on the top ?  Then what you say makes 
sense, as true the largest main content define it's grade (grain size). 
However it's difficult to define what extend or amount we should 
consider as "loose".
Many roads have the gravel completely embedded, interlocked in the top 
layer, especially those using clay like top or sealing. The purpose 
mainly making the surface more smooth, fill the voids with the clay.  
The gravel might be a natural mixture, or a mixture where the grade 
doesn't matter that much.  It is added to provide more stability and 
prevent washing out.  In dry conditions it's very hard to see by a non 
professional if there is any gravel at all, they look much the same as a 
complete dirt road with clay layer.  In those cases do we still tag it 
as gravel, fine-gravel ?  Or just as f.i. murram , sand or other ? It's 
hard to determine the grade, they might be naturally present large 
boulders or rocks but the gravel content or it's grade is impossible to 
determine without taking a larger sample from the top layer.  So that's 
my point, defining gravel, fine-gravel or embedded garvel boulder 
mixture, where does it leads us, what sense does it make besides visual 
appearance to add it to OSM ?

Greetings,

Bert Araali

On 27/04/2021 10:07, Martin Koppenhoefer wrote:
>
> sent from a phone
>
>> On 27 Apr 2021, at 02:35, Bert -Araali- Van Opstal <bert.araali.afritastic at gmail.com> wrote:
>>
>> So saying a road surface is gravel or fine-gravel is essentially wrong, because it's a mixture.
>
> while this is completely true, my interpretation always was the grain size indication was about the biggest grain that one can encounter in significant quantities (i.e. a single larger stone is just an obstacle on the surface, but occurring systematically it counts)
>
> Cheers Martin
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