[mkgmap-dev] Strange behaviour in multipolygon

Wed Apr 24 13:49:00 BST 2019

Processing a small area in my region, I noticed a strange behaviour in the
rendering of one multipolygon. In the original OSM map (see image A.jpg,
bounds are 43.9978 to 44.0135, 10.2989 to 10.3228) the area along the
street to "Cardoso" is a strip of empty land (untagged) sorrounded by a
forest. This forest is a large and complex multipolygon tagged with
natural=wood. Thus, the strip of empty land is defined by lines which are
the outer members of the multipolygon (see file cardoso.osm). When
processed with mkgmap, the result is somehow "inverted": the map shows the
strip of land as wood and the area around as empty, both in Basecamp and in
my eTrex 20x (see image B.jpg). To test the issue I created a simple style
(see files polygons and points) containing only the file "version", the
file "points" which defines only the rendering of places and the file
"polygons" which defines only the rendering of the areas tagged with
natural=wood. I cannot figure out if the problem lies in mkgmap or in the
incorrect mapping of the area in OSM. By the way, the area is correctly
shown in many online maps deriving from OSM data and also in the OpenMTBmap
which I downloaded and installed in Basecamp. I'm definitely stuck. Any
suggestion on how to solve the problem?
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