[mkgmap-dev] Option "preserve-element-order"

Tue Jun 30 22:45:49 BST 2009

Thank you for all the quick feedback.

What I am after is the drawing order of lines.

I use the overlay feature of mkgmap with the "overlays" style file.  
Using this feature one way in the OSM data will create several ways  
with an identical location in the IMG file, but with different Garmin  
IDs. Those ways get always added in the same order to the IMG file. So  
I should be able to use this feature to create more complex line  
styles by overlaying Garmin IDs. Another thing I use is a patch that  
allows me to generate ways from relations (I've published it some time  
ago on this mailing list). The relations are handled before the  
points, lines and shapes are handled, so they are always first in the  
IMG files.

The thing is: It doesn't work. What is even worse is that I get  
different drawing order whether I view the map on the computer or on a  
GPS unit. Attached are some screenshots of the same area using the  
same IMG files. The thing to look at are the cycle route in blue  
(generated from relations) and the cycleways that go alongside roads  
(the blue dotted lines on both sides of a way, generated as an overlay).

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MapSource and RoadTrip draw the cycle way at the bottom of the screen  
(along Hofmannstrasse) behind the road, but the n?vi 255W and the  
Oregon 300 draw it on top of the road. The same is the situation with  
the cycle way at the upper left corner (along Gebbertstrasse). On the  
computer it is drawn behind the road while the GPS units draw it on  
top of the road.

It would be nice if that behaviour would be at least consistent. But  
it isn't. I also get roads drawn on top of the cycle routes on the GPS  
units.

Has anybody any idea what is happening here?

Regards
Thilo