[Tagging] Route members: ordered or not

marc marc marc_marc_irc at hotmail.com
Thu May 3 17:10:32 UTC 2018

"impossible" only due to missing tools to be able to do the job
and the time it take do it "by hand"
try to order this one http://www.openstreetmap.org/relation/1744381
I spent a little time sorting these members, but it's a waste,
it's deteriorating faster than it's getting better.

Le 03. 05. 18 à 18:49, Colin Smale a écrit :
> Why does a loop make it impossible to sort the ways? It implies that a 
> section of the route is present twice in the relation, but there is 
> surely no distinction between the first traversal of a way and the 
> second traversal?
> On 2018-05-03 18:42, Volker Schmidt wrote:
>> I will try to explain this in a more systematic way:
>> Routes belong to either of two categories:
>> (A) Those whose members can be sorted into a single ordered sequence
>> (B) Those that cannot be sorted into a single ordered sequence of members
>> Sorting makes only sense for category (A)
>> Routes of type (B) can be subdivided into routes of type (A), each of 
>> which can be sorted, but the overall route can not be sorted.
>> Routes are of type (A) if
>> (1) the path from begin to end is identical to the reverse path with  
>> all members traversed in the reverse order and in the opposite direction
>> or
>> (2) all members have the role forward
>> or
>> (3) all members have the role backward
>> Any route
>> (1) that has more than two ends
>> or
>> (2) that contains any loop (except the case that the entire route is a 
>> single loop)
>> or
>> (3) that contains any element with role forword or role backward 
>> (except the cases of all-forward or all-backward)
>> or
>> (4) that contains node or area elements
>> is of type B
>> I am not sure if I have taken care of all cases - please complete as 
>> necessary
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