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[mkgmap-dev] Garmin uses overlapping tiles

From Gerd Petermann gpetermann_muenchen at hotmail.com on Tue Feb 6 14:32:43 GMT 2018

Hi Andrzej,

hard to say where exactly the DEM area ends on the right / bottom side.

I got the info about 0x4a polygons from GPSMapEdit looking at the basemap.
MapSource shows the tile boundary more or less exactly at E16.5, so I have no idea
whrere the 0x4a value comes from.

I don't plan to change splitter, I want to change the TRE file written by mkgmap.
Working on a patch right now ...


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Dienstag, 6. Februar 2018 14:57
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] Garmin uses overlapping tiles

Hi Gerd,

I have some questions.

Is TRE area bigger than DEM area or tiles overlap but still DEM area is
bigger than TRE? It looks like overlap is 4 Garmin's units, this is less
than DEM raster size.

 > The next interesting point is that the 0x4a polygons of these two
 > tiles do NOT overlap.
 > They seem to share  768896 (!).

Is it a typo? I guess: polygon 0x4B and 768856

Does map data overlap too, or this is only extended rectangle size
written to TRE header? If backgrounds don't overlap, maybe real map data
don't either. If I get border value right, than maybe tile is extended
only at left and top border?

What about routing nodes, if splitter creates overlapped tiles? I think
there should be an external routing node where road crosses tile border.
There would be mismatch, if tiles overlap.

Best regards,
mkgmap-dev mailing list
mkgmap-dev at lists.mkgmap.org.uk

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