[mkgmap-dev] highway count not fixed yet... - merge-roads-branch

Sun Sep 29 12:01:17 BST 2013

> WanMil wrote
>> Hi Gerd,
>>
>> in my opinion recalculating the highway counter after removing the short
>> arcs should fix all problems, shouldn't it?
>
> Don't think so. All routines that replace or add points after that must
> make sure that they maintain the correct highway count.
>

Ok, which routines perform such modifications? I couldn't find any such 
modifications of MapRoad instances after the StyledConverter.

>
>
> WanMil wrote
>> I've added three changes to the patch:
>> 1. When calculating the highway count ways with duplicate id are not
>> considered. This avoid that all points of a duplicated way are preserved
>> by all filters.
>> I think this should be modified a bit. For the first and last point of
>> those ways the highway count should be increased and also all points
>> where another way is connected. I have no use case where this matters
>> but I think it is the "correct" counting?
>
> No, it just increases the possibility that the counter overflows.

Maybe that's true for the trunk but in the branch there are real cases 
where it matters.

Assume the following two ways:

x>>>>>>>>>x===========x
1         2           1

(x = Node; >> oneway line; === oneway=no; highway count below nodes)

The style might duplicate the oneway=no way into to oneway=yes ways

            >>>>>>>>>>>
x>>>>>>>>>x<<<<<<<<<<<x
1         2           1

The merger might merge two of the ways:

            <<<<<<<<<<<
x>>>>>>>>>x>>>>>>>>>>>x
1         1           1

As a result the highway count of the 2nd and 3rd node is wrong. It 
should be 2 instead of 1. And AFAIK this difference matters.

> Maybe we should not use this counter at all. The information that
> it "hides" is that a point connects two or more roads.
> I think a better solution would be to have a method markRoutingNodes()
> which uses the counter and sets a bit flag in the coord instance.
> This routine would replace setHighwayCounts() and resetHighwayCounts().

I don't understand the advantage? I think maintaining the highway count 
is the same like markRoutingNodes(). How do you want to know when to 
call markRoutingNodes()?

>
>
> WanMil wrote
>> 2. I have added the problematic point in the error message of the
>> MapBuilder in case a node is not a CoordNode. Just having the way id
>> might not be enough information and the way also might have been merged.
>>
>> 3. I have moved the recalculation of the highway counters after the
>> merge procedure. This should not change anything but it avoids a problem
>> with merging...
>
> This is a good idea. Maybe do it before and after? That also means that
> decHighwayCount() is obsolete, doesn't it?

decHighwayCount() is obsolete as long as the highway counters are 
recalculated after mergeRoads(). When recalculating the highway count 
after mergeRoads() the RoadMerger does not care about (correct) highway 
counts (maybe a perf improvement might require correct highway counts 
but I don't know if the improvement is neccessary).

>
> Gerd
>
>
>