Hi Marko, Thanks for the explanation of things. Let me reply inline to some specific comments. On Wed, Jul 6, 2011 at 9:15 AM, Marko Mäkelä <marko.makela@iki.fi> wrote: [snip]
If you have have cycyleway that is tagged with 'access = yes' - meaning the public is allowed use that cycleway - the 'add access = no' rule will not overwrite the access rule in the OSM data and the cycleway will be routable by motor vehicle.
Isn't it a bit redundant to add access=yes to ways? Usually, you would add access restrictions. I would say that this is a problem in the map data.
This is a good point. Looking at the taginfo: http://taginfo.openstreetmap.org/keys/?key=access#values 'access = yes' is definitely being and it seems to be a valid tag/value pair according the wiki. I think it would be a good idea to remove the 'access = yes' from the OSM data. Perhaps we could remove this tag/value pair when mkgmap is reading in the data? That way all of the ways will be "normalized" to mean 'access = yes' if no access tag is present. And then we could keep 'add access = no' for the cycleways which would give the correct behaviour. I can see that my 'set access = no' with overwrite other types of access like 'access = destination' so it's not a good way forward. Thoughts? I'd be happy to make the patch.
I think it would be better to use the motor_vehicle tag to determine if a cycleway is routable by car.
To my understanding, mkgmap does not observe the motor_vehicle tag at all. It obeys motorcar and motorcycle. I do not know what happens if they contradict. As far as I understand, the Garmin map format cannot distinguish motorcar and motorcycle.
Is it correct to use motor_vehicle instead of the more specific motorcar or motorcycle? A snowmobile is also a motor vehicle, but (depending on legislation) snowmobiles are not necessarily allowed on ways that are allowed for cars and motorcycles.
The more specific motorized vehicle tag (e.g. snowmobile) takes precedence. I guess the moter_vehicle tag is mostly useful for indicating that all motorize vehicle traffic is prohibited on a given way.
Come to think of it, for simplicity access=* should probably cover 'normal' vehicles. Motorized terrain vehicles should rely on specific tags, such as snowmobile=yes.
That sounds reasonable.
We'd still have to support the OSM access tag somehow. I did a quick grep through the mkgmap source and it seems that there isn't support of the motor_vehicle tag. I would like to make a patch to address this issue but I have a couple of questions first. Is the access tag used to describe motor vehicle access in mkgmap? Does the garmin format support the idea of public / private access separately from motor vehicle access?
My understanding is that Garmin supports a few modes of transportation: foot, bicycle, motorcycle/motorcar, emergency, and possibly some others. Each mode has access bits, something like yes/destination/no.
Good to know. Thanks, Ben