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Holes and complex polygons

robertfordrobertford Global Mapper UserPosts: 5 ✭✭
edited April 2008 in Vector Data
When I load ESRI shapefile hydrography data and assign it a feature type, Global Mapper seems to misinterpret subtractive holes or "islands" in the data, resulting in irregular shapes. Here is an image of this problem as it applies to southern Florida.

I believe that these subtractive area polygons are ordered counter-clockwise according to the ESRI standard. Is there any way to configure Global Mapper to treat these areas as holes?


  • global_mapperglobal_mapper Administrator Posts: 17,238BMG Staff ✭✭✭
    edited April 2008
    Global Mapper should automatically treat counter-clockwise oriented areas features in a multi-part polygon feature from a Shapefile as holes in a parent area, provided that the hole is properly defined and fits inside the parent that it is supposed to. I have seen lots of incorrectly defined Shapefiles in regards to parent and child polygons in the past and Global Mapper has a lot of code to try and sort out exactly what was meant when a multi-part polygon was encoded rather than what the exact correct behavior would be according to the Shapefile specification, but some encodings with improper hole definitions still don't work.

    If you can send me the Shapefile in question I can take a look.


    Global Mapper Support
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