[mkgmap-dev] Change mkgmap default options to make mkgmap more userfriendly

Fri Apr 30 15:32:07 BST 2010

Felix Hartmann <extremecarver at googlemail.com> writes:

> On 30.04.2010 15:22, Greg Troxel wrote:
>> so we really need a tag for typical_speed, because you're saying that
>> speed limits and typical speeds are not all that well correlated.  This
>> is not really about mkgmap.
>>    
> Well of course. What I'm saying is that taking maxspeed to set the 
> road_speed in mkgmap, makes no sense at all. Actually typical speed is 
> not needed, because a clever style-file can guestimate the typical speed 
> very well (except rush hour and night). I think the maxspeed treatment 
> is important, but it has to depend on the type of road. Knowing maxspeed 
> is 80km/h or higher, enables us to be certain we look at a highway 
> outside of a city-limit, which of course will have higher typical speed 
> than a highway inside city limits - so maxspeed is very important in 
> assesing the map data. However it is useless for using to directly set 
> the road_speed (in NT maps, Garmin is using a seperate maxspeed, while 
> the road_speed is supposed to keep care of typical speed).

All of that has region-dependent knowledge about the relationships
between road types, legal maxspeeds and the typical speeds.  It's quite
clear that your world and my world are very different and that your
rules won't work in my world - in the US a road posted at 50 mph can
reasonably safely be assumed to be travelable at 55 mph unless congested
due to being in a city.  That's all fine, but I think argues that we
really need typical travel speeds in the database.
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