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[mkgmap-dev] type=through_route relations and mkgmap r3743

From News news at pointdee.co.uk on Tue Jan 10 10:55:06 GMT 2017

If I remember correctly the idea of a through_route was first raised by 
Mark Burton a few years ago. It was intended to solve the problem of 
which is a situation where you have to turn off the carriageway you are 
currently travelling on in order to stay on the same named road. In 
these circumstances it is (almost) impossible for any routing engine to 
deduce that it needs to give you a routing hint in order for you to stay 
on the road that you are currently on. At the time I had a couple of 
these near me where I knew that my Garmin was effectively missing a turn 
and hence you would end up travelling in the wrong direction. Adding a 
through_route at these places fixes this problem.

There is also a secondary use where a road e.g. Smith Road, bends 90 
degrees and you are sometimes told to turn left/right to stay on Smith 
Road even though there is no turning

A few years ago I tried to get this accepted into the list of official 
tags however the vote resulted in a draw and I didn't have chance to 
pursue it further.

I have now moved and there are none currently near me that I could use 
to check if this is still working

See also......



On 01/10/2017 08:31 AM, Gerd Petermann wrote:
> I found one that might be interesting:
> https://www.openstreetmap.org/relation/406379
> If I got that right the intention was to tell mkgmap that
> it should change the bearing (heading) values in the map so that the Garmin
> algo doesn't produce a
> hint like "Turn left onto Calle Botánico Rivas Mateos" when travelling from
> way 24647941 (Calle José Luis Cotallo) to way 24311294 (Calle Botánico Rivas
> Mateos).
> (this is what happens now)
> What would you want instead?
> @Carlos: You have created that relation in 2010, maybe you remember?
> Gerd
> Gerd Petermann wrote
>> Hi all,
>> I've noticed that mkgmap still checks these relations for correctness but
>> they have no influence on the created map.
>> Part of the code that handled them was removed with r3649:
>> http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=3649
>> If your map was created with r3743 or later, please check if you find a
>> crossing with such a relation which where routing
>> hints are wrong. In that case I would try to add code for the support,
>> else some unused code can be removed.
>> Gerd
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