[mkgmap-dev] Turn Restrictions using three ways - design guide for OSM mappers?

Fri Oct 11 07:35:39 BST 2019

On Wed, 9 Oct 2019, Gerd Petermann wrote:

> I still think both restrictions are probably not correctly mapped, but
> that's a different story now.

Thanks, this is what I wanted to know, if the original mapper made a 
mistake or not - I'm concerned because of the apparent handling 
discrepancy between different tools.  But what I didn't know before this 
is that the Garmin doesn't directly support the only-X construct.  This 
changes my opinion about this.

> I try to find a way to add the additional restrictiions to the IMG file.

No worries, I just wanted to make sure that if anyone fixes OSM data due 
to a warning in mkgmap that it is a real violation of methodology (like a 
restriction relation that was missing members/less than 3 members), not 
because of a Garmin limitation of some sort.

I see that there was a code change proposal, I wish I could run it but I 
don't have the capability to do so at this time.  However from the 
programmer side of me I'm a bit concerned about handling changing only-X 
-> multiple no-Y's because of potential errors in mapping causing a huge 
bloat of erroneous restrictions.  At this point I wouldn't touch the 
multiple via ways (relation having two or more vias ways) even though it 
is also "supported" by OSM data, not sure if it should be handled, as it 
may be an error.  I've also seen some fairly complex interchanges that 
have these via-as-way and hope that the code does the right thing every 
time.  I'd probably only limit this to one way-via only-X restrictions if 
anything - if there is any uncertainty on how to handle this, just leave 
it the way it was!

Thanks for helping me understand this better, I didn't expect any code 
edits, especially if the Garmin doesn't support these directly.