[mkgmap-dev] Maintaining generated sea polygons

Fri May 21 18:34:55 BST 2010

Hi,

I don't know if this is the same problem as Nop described,
but lately I found that on my map some sea areas were gone in the Netherlands:
see http://img338.imageshack.us/img338/9992/errorcoastline.jpg

On osm it looks ok:
http://www.openstreetmap.org/?lat=52.817&lon=4.955&zoom=10&layers=B000FTF

Im using the geofabrik abstract from europe to compile my benelux map,
Any idea how to fix this? I tried another abstract (planet-benelux) but this gave the same results.

Is it caused by the splitter? Is it an error in de osm data?
In the mkgmap args i use generate-sea: no-mp,extend-sea-sectors,close-gaps=1000
and it never went wrong except for the last two weeks.

Nop wrote:

Hi!

I have been playing around with generated sea polygons. The algorithm works
remarkably well - but I have been experiencing trouble due to inconsistent
use of natural=coastline in the data.

There was an invalid use of natural=coastline in the planetfile, that caused
a whole tile in the Alps to be flooded. So I tracked it down, fixed it and
waited for the next planetfile. This time another tile near Berlin was
flooded. I tracked it down, noted that another mapper had already fixed it
and waited for the next planetfile. This time another tile south of Würzburg
was flooded... - you note the pattern? :-)

For three weeks I have been unable to grab a planetfile with correct
coastline for central europe - they are broken at about the same speed we
can fix them. So even though I was able to build a really nice map a while
ago, all update attempts were broken.

Therefore my question: Would it be possible to save the generated sea
polygons to disk in osm format so an intact set of polygons can be re-used
with future osm data? That way it could be ensured that future updates will
have the same, correct sea polygons and not be randomly broken by temporary
inconsistencies in the osm data.

Storing the image files and using them as a seperate map layer is not a
solution as older Garmin devices are really cumbersome with layers or cannot
handle multiple layers at all - and the map is for an older device.

Any ideas?

Nop

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