mask from two shapefiles

sjfsjf Global Mapper UserPosts: 10
edited October 2012 in Technical Support
Hi, I need to create a mask file to export / tile only selected area's from a file. I have made an empty mask file (one big square) and I have the shapefile with the area's I want to cut out of the mask. This way I get a shape with holes I use to overlay on the file I want to export / tile. The parts I don't want to export / tile are obscured (black) and will be transparent (so not visible or tiled.

How do I go from two files, union them and then only get the mask file with holes to overlay. (p.e. the holes are buildings).
greetings,
Stefan

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2012
    Stefan,

    It sounds like you just need to add the mask areas as holes/islands to the larger big square. To do this, simply load them all, select all of the mask areas, then right-click and select the Crop submenu option to Subtract/Add Islands, then click in the big square area to make the mask areas holes in that. You will then have a single crop area consisting of the big square with the smaller mask areas cut out of it.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • sjfsjf Global Mapper User Posts: 10
    edited October 2012
    Is this true?
    Mike I tried what you said (using v13.2): I have 48.000 houses I want to cut out of a simple square mask shapefile. Selected them using the digitiser tool, right clicked and selected 'cut selected areas from another area' - clicked the square and selected yes to 'mark as deleted'.

    Then within less than a second (!!) the operation is completed? I saved the square as a new mask and checked if this was really true. I did this 3 times because I could not believe it could work that fast... (it takes about 1 hour to do this in arcview...).
    Am I doing something wrong or is it really that fast (and how does GM do that?). Thanks Mike.
    greetings, Stefan
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2012
    Stefan,

    It's really that fast. If all of the areas that you selected to 'cut' are completely inside the designated parent area, all that it does is add them as holes into that parent, nothing compute intensive required if your polygons don't have a ton of vertices.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
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