[mkgmap-dev] Drive-on-left

Fri Nov 15 01:08:52 GMT 2013

Hi,

WanMil wrote:

 > attached patch forwards the "guessed" drive-on-left value in a thread
 > safe way to the NOD header by using a ThreadLocal variable. This is a
 > small code change.
 > Anyhow this makes only sense if you think that the guess algorithm is 
 > ok.

Shouldn't it be a TRE header? Or TRE header too?

According to help for options, guessing is connected with 
"check-roundabouts", which revers directions of roundabouts. This option 
is wrong for tiles, that contain multiple countries with different 
drive-on rules. In that case "check-roundabouts" would damage some good 
roundabouts.

If you make a map for a single country, you don't need guessing. And you 
can't invoke guessing for a map with multiple countries. So this 
guessing feature looks rather redundant.

In my opinion there should be no guessing but a simple count. If a tile 
has more than 50% of roundabouts as drive-on-left, then this tile should 
be marked as drive-on-left. That way most of roundabouts would look 
correctly when navigating.

Perfect solution would be to make tile splitting along country border. 
But if we can't do that, then maybe we could get statistically best 
settings for drive-on flags?

-- 
Best regards,
Andrzej