[mkgmap-dev] benefit of --drive-on-left

Thu Jul 12 12:56:20 BST 2012

There is one cosmetic difference I have noticed. The roundabout junction 
diagram in the top left of the Garmin screen always reflects the 
drive-on-left/drive-on-right mode. If I compile a map for the UK without 
"drive-on-left", the spoken and written routing instructions are correct 
(so turning right at a roundabout will be "take third exit") but the 
little icon will reflect taking the roundabout in an anti-clockwise 
direction.

Another reason for using it is for motorway exits. If you have a fork 
between (for example) two motorway_links you can normally assume (as a 
heuristic) that the left fork (driving on the left) is the "exit" and 
the right fork is "straight on".

If neither drive-on-left nor drive-on-right is specified, mkgmap uses 
the first roundabout it encounters to work it out.This COULD go wrong, 
although it is unlikely. The bounding box for the UK includes bits of 
France so it may depend on what the splitter puts in the first tile. 
Just in case it is good to have a way of setting this explicitly.

Colin

On 12/07/2012 13:33, Frank Fesevur wrote:
> 2012/7/12 aighes <osm at aighes.de>:
>> what is the advantage of using --drive-on-left?
>> I think routing shouldn't be influenced, because oneway=yes should be
>> obvious and on normal roads/ways there shouldn't be any difference at all.
> What about roundabouts? Routing a roundabout and saying "first exit"
> or "third exit" is a major difference.
>
> Don't see much other things though.
>
> Regards,
> Frank
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev