[mkgmap-dev] Wrong_route_calculation / strange straight routing lines on GPS

Thu Jan 29 15:57:43 GMT 2009

Robert Vollmert schrieb:
> On Jan 28, 2009, at 23:10, Gert Münzel wrote:
>> making my first steps with mkgmap that, although the routing works 
>> fine in Mapsource, i get in trouble on my Gps unit Garmin gmap60csx. 
>> Very often i got these strange straight magenta routing lines in 
>> between normal routing.
>> Meanwhile i figured out that it seems to be that t has something to do 
>> with the length of a polyline. I don't know if it is the count of 
>> points/nodes of the polyline or still the lenght or both.
>> But comparing the same mp-file once compiled with mkgmap, once with 
>> cgpsmapper i see, that cgpsmapper split these long lines during mkgmap 
>> leave them like they are.
> 
> How did you compare the IMG files? Have you tried decompiling the broken 
> IMG with test.display.*? Have you tried manually splitting the polylines 
> in the .mp-file? Does it help?
> 
> My guess is that the problem lies with long polylines (in the .mp-file) 
> that are split into several polylines (in the IMG) by mkgmap, which 
> results in a road made up of several polylines.
> 
> But if I understand you correctly, maybe the problem is just with long 
> polylines in the IMG file?
> 
Hi Robert,

1.)I compared the two files by using GpsMapedit opening the img-files 
and had a look on Polylines where the problems occurs.
2.)Yes, splitting the data manually helps but is not a usable solution
3.) No, vice versa, the problem is that mkgmap doesn't split that long 
polyline like cgpsmapper it does.
4.)Actually it seems to me, that the problem really depends on length 
and/or count of nodes of the polyline.

cheers Gert