[Tagging] Definition and usage of Key:mtb:scale:imba?

[brad]

I've never seen an official IMBA rating on a sign.
I see both mtb:scale and mtb:scale:imba both used.   The wiki for 
mtb:scale doesn't make sense.   It's either skewed for extremely extreme 
riding or they don't understand gradient.   It says that for 
mtb:scale=1, gradient<40%.   This is meaningless.   Nobody can ride up 
an unpaved grade that is 40%, or probably even 30%.   A steep trail is 
15%.   A really steep, almost unrideable, very difficult hiking, trail 
is 20%.    Going downhill, anything above 25% is a double black, only a 
small percentage of riders can ride, unless it is very smooth with 
really good traction.

The tag has been used with common sense, but inconsistently, instead of 
the wiki definition.

In the US, we us a green/blue/black/doubleBlack system which I would not 
consider an IMBA system, but merely a subjective rating by whoever made 
the map,  usually a local mtb club or land manager. IMBA probably 
clarified it, but it probably predates IMBA.   The apps trailforks and 
mtbproject use green/blue/black/doubleBlack ratings as determined by the 
users.  For the most part it's consistent, but one does have to be 
cognizant of the local bias.
The imba rating system was not invented for bike parks, so the OSM use 
for bike parks doesn't make much sense.

In my opinion, mtb:scale:imba could be deprecated, and the wiki for 
mtb:scale updated & clarified.

On 4/22/20 5:00 AM, Simon Poole wrote:
>
> IMHO, the problem is using mtb:scale:imba 
> <https://wiki.openstreetmap.org/wiki/Talk:Key:mtb:scale:imba> in place 
> of mtb:scale for normal trails which I suspect the intent of the 
> original wording was to avoid that happening.
>
> Simon
>
> Am 22.04.2020 um 10:53 schrieb Andrew Harvey:
>> I've been using mtb:scale:imba on any kind of trail where signage at 
>> the site notes an IMBA rating, in this way it's verifiable based on 
>> the sign. I don't know what "bikepark" and "north shore" mean here 
>> but while some of these trails which have an IMBA rating can be 
>> consider together as part of a collection of trails and that 
>> collection does have a name sperate to the individual tracks (which I 
>> guess is what bikepark means) others which do have signposted IMBA 
>> ratings are standalone and not part of a named collection of trails.
>>
>> So if it has an official or signposted IMBA rating, it should be 
>> tagged regardless of the trail being "natural" or with "artificial 
>> obstacles" and regardless if it's part of a mountain bike "park" or not.
>>
>> On Wed, 22 Apr 2020 at 17:29, Joseph Eisenberg 
>> <joseph.eisenberg at gmail.com <mailto:joseph.eisenberg at gmail.com>> wrote:
>>
>>     Another user would like to redefine the definition of
>>     "Key:mtb:scale:imba"
>>
>>     See suggestions at
>>     https://wiki.openstreetmap.org/wiki/Talk:Key:mtb:scale:imba:
>>
>>     This tag was approved in the proposal
>>     https://wiki.openstreetmap.org/wiki/Proposed_features/mtb:scale -
>>     with the description "The IMBA Trail Difficulty Rating System
>>     shall be used for bikeparks. Especially for North Shore. It is
>>     adapted to mtb trails with artificial obstacles. For "natural"
>>     trails it is advised to use the mtb:scale/mtb:uphill:scale." -
>>     linked to
>>     http://www.imba.com/resources/trail_building/itn_17_4_trail_difficulty.html
>>
>>     Can other mappers who use this tag frequently confirm whether it
>>     is limited to specifically designed and built bike trails, like
>>     those found in "bikeparks"?
>>
>>     -- Joseph Eisenberg
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