Global Mapper Pro

I'm having a problem trying to convert holes/islands to a polygon

digitalaviator Global Mapper UserTrusted User
edited October 2015 in Technical Support
I'm using GM 15 and I've need to turn an island area in a polygon into an polygon for the island.

According to the help file it says:

Converting Areas with Islands to Single Vertex List
If one or more area features with separate islands/holes within them are selected, the Create Single Vertex List Area From Selected Area(s) With Islands option will appear in the Advanced Feature Creation sub-menu of the right-click menu. When selected, this option will connect all of the islands/holes within the selected parent areas into a single vertex list and replace the original parent/island area with a new area that contains just that single vertex list. This is useful for converting areas with islands into a form that software that cannot handle areas with holes can make use of.

However whenever I select the polygon with multiple islands in it, the "Create Single Vertex List Area From Selected Area(s) With Islands" does not appear at all. The same thing when I select the island/hole and attempt the same thing, I get no "Create Single Vertex List Area From Selected Area(s) With Islands" option in the Advanced Feature Creation sub-menu

Is there something I'm doing wrong? How can I go about this the correct way? As I'm definitely going to need to generate islands for the NHD data for Florida and manually converting areas to lines and then back again to achieve the goal as a work around is going to be a crazy approach :wink:


  • bmg_bob
    bmg_bob Global Mapper Programmer
    Global Mapper does not have a function to create a polygon from a hole/island, but here is something you can try:

    1) Select one or more holes/islands.
    2) Right-click and select Create Line Features->Create Line Feature(s) from Selected Area Feature(s).  Your new line features will be automatically selected.
    3) Right-click and select Create Area/Polygon Features->Create New Area Feature(s) from Selected Line Feature(s)
    4) Both the new line features and new area features will be added to the User Created Features layer.  Open the Overlay Control Center, select the User Created Features layer, right-click and choose Export Selected Layers to New File.  I recommend exporting to a shapefile because that will let you separate the lines from the areas, and let you just keep the areas the represent your islands.

    Note: I did this with Global Mapper 17, but these functions have been around for a while, so I expect that it works in v15 as well.
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