[mkgmap-dev] Missing prompt when joining major road from minor road at an angle

Mon Sep 7 14:41:44 BST 2009

Greg Troxel wrote:
>   I've got a case locally where a tertiary road meets a primary road at a 
>   shallow approach-angle of about 30 degrees. The Garmin does not announce 
>   the junction [...]
>
> I have seen this with garmin's proprietary maps.
>   

Ah - so it's Garmin's announcement-engine that makes the decision is it?

OK.

I have a request. ( There may be code floating about which will 
implement this without too much heartache too... )

Could mkgmap examine junctions between roads of different class, find 
the angle-of-approach (AOA), and if AOA < some magic number (maybe 30 
degrees) then slip an extra node into the more minor road just by the 
junction so as to make the junction itself happen at 90 degrees?

I ask this because in addition to getting missing warnings on some 
junctions, I also get quite a few bogus "keep left/right" instructions 
where a minor road (sometimes just a farm track) meets the more major 
road at a narrow angle, but it's obvious to any driver that you don't 
deviate from the more obvious road unless instructed to do so.

Some code like this was tried back in about April as an attempt to 
improve the driving instructions on roundabouts, and maybe motorway 
exits. That code might be re-usable here.

I'd suggest avoiding doing the AOA fiddling described above if the 
"minor" road is an XXX_link and the "major" road is an XXX, BTW.

Steve