[mkgmap-dev] More on Routing

Fri Jul 17 15:12:07 BST 2009

Steve Hosgood wrote:
> Mark Burton wrote:
>> Hi Paul,
>>
>>  
>>> Bury to CHester however starts along the M66, goes straight through
>>> junction 18 to the next junction where you go all the way round the
>>> roundabout, come back on yourself to junction 18 and then turn left onto
>>> the M60 where the route is then as expected.This odd behaviour then
>>> continues if routing to places further afield that require the same
>>> initial route.
>>>
>>> http://www.openstreetmap.org/?lat=53.5497&lon=-2.261&zoom=14&layers=B000FTF
>>>
>>> shows the junctions involved but I can't see how it can be data errors
>>> as some routes go M66, M62 westbound without problem and all 3
>>> destinations mentioned above are on the same tile
>>>     
>>
>> Can't explain why
>> you're seeing badness there.
>>
>>   
> 
> I might.
> 
> If Paul used XAPI to extract a part of the country in order to build his
> Garmin map then it's possible that his XAPI excerpt isn't complete. I've
> been seeing more and more of this happening in South Wales where I'm
> doing exactly that.
> 
> It seems (from other comments here) that there's a known problem with
> the various XAPI servers occasionally dropping a minute-diff and never
> recovering. I've seen this happening since the switch to the 0.6 API: I
> had never noticed it before that.
> 
> I've been sent on bogus routes around Swansea (my home town) due to
> small bits of roads going missing. I've got a partially missing
> westbound carriageway on a dual carriageway in one particular case, I've
> also spotted a missing urban one-way street and a few other cases.
> 
> If Paul looks carefully, does he spot (on the Garmin) a missing
> slip-road on a roundabout, responsible for there being no valid route
> from one side of a dual carriageway? Worse is an apparently present
> slip-road on a dual carriageway where the 'oneway' once pointed the
> wrong way, but has been fixed on OSM at some point, but where the fix
> was part of a minute-diff that the XAPI server dropped?
> 
> Steve
> 

I use the Geofabrik mirror to download the great_britain.osm from
http://download.geofabrik.de/osm/europe/great_britain.osm.bz2

I then use splitter r33 and usually the most current mkgmap to compile
my maps using

time java -Xmx2048M -jar -enableassertions mkgmap.jar --latin1
--gmapsupp --route --region-name="Great Britain" --region-abbr="GBR"
--remove-short-arcs --stylefile=$stylefiles --max-jobs --net
--code-page=1252 --country-name="GREAT BRITAIN" --country-abbr=GBR
--tdbfile --tdb-v4 --description="Map of GB" --family-name="Great
Britain" 700000??.osm $srtmdir/uk*.osm

This also wouldn't explain why I could route from Bury to Roe Green
turning west at J18 yet Bury to Chester goes straight through that
juction only to turn round at the next and come back to J18 and then go
past Roe Green

Cheers

Paul