> [email protected] schrieb am 27.09.2010 15:20: >>> As an example take a nature reserve consisting of a wood with a lake inside. >>> This migth be mapped with two polygons and a relation: >>> polygon A: leisure=nature_reserve (the complete area) >>> polygon B: natural=water (only the inner area) >>> multipolygon relation: natural=wood and outer=polygon A and inner=polygon B >>> (only the surrounding area) >>> >>> Right now polygon A seems to be missing in the resulting map. >>> >> But how would mkgmap know which of the two outer polygon types to use >> (ie nature reserve or wood)? > > It should use both: > > The nature reserve should cover the complete area. > > The wood should cover only the area defined by the multipolygon. > > This is (one of) the intended tagging of the multipolygons. Allowed > alternatives > (with the same logical interpretation) would be: > > 1. You could use an additional polygon for the outer limit of the multipolygon > (polygon C) which would have the same nodes as polygon A. Polygon A and B > would > stay unchanged. > multipolygon relation: natural=wood and outer=polygon C and inner=polygon B > > 2. You could put all tags from the relation on polygon C, polygon A and B > would > stay unchanged. > polygon B: natural=wood > multipolygon relation: outer=polygon A and inner=polygon B > > 3. You could move the nature reserve tag into the multipolygon area and the > inner area. > polygon A: > polygon B: natural=water and leisure=nature_reserve > multipolygon relation: natural=wood and leisure=nature_reserve and > outer=polygon > A and inner=polygon B > > 4. And you could move the tags from the relation of variant 3 to the outer > polygon. > polygon A: natural=wood and leisure=nature_reserve > polygon B: natural=water and leisure=nature_reserve > multipolygon relation: outer=polygon A and inner=polygon B > > I think these five possibilities are all allowed under the actual accepted > multipolygon scheme and they should all result in nearly the same garmin map. > (Alternative 3 and 4 split the nature reserve into to areas, but in the end it > covers teh same area). > > Gruss > Torsten
Hi Torsten, I am back and I have thought about your request. It would be possible to implement a patch which keeps the original polygons in case they are tagged differently to the multipolygon. I have also read Charlies answers and before digging in the code I would know if this feature is really needed and useful? Can you estimate how many multipolygons are affected? WanMil _______________________________________________ mkgmap-dev mailing list [email protected] http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
