Create new polygons from intersecting polygons

rivercreekoceanrivercreekocean Global Mapper UserPosts: 4
edited February 2013 in Vector Data
I have two shape-files, both consisting of polygons. I want to use the polygons from one file to create new boundaries in the polygons from the other file, where they intersect.

For example, if I had a large river polygon that ran through four counties, I would want to break that river into four polygons (and not have the original, single polygon anymore, so that only the four river polygons and four county polygons remained) with boundaries along the county lines. I'm aware that it's possible to crop polygons with polygons, and I could possibly achieve something similar by doing this one-by-one for each county. However, the data I am processing contains thousands of counties and doing so one-by-one is impractical.

Is this possible in global mapper? And did that make any sense?

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited February 2013
    Yes what you can do is select all of the county polygons with the Digitizer Tool, then right-click and select the Crop submenu command to Crop Loaded Features. Then you can crop all loaded areas (other than the selected ones) to the selected areas, which should split your river up into separate pieces based on the crop with each county polygon. If you choose to mark the original areas as deleted your original river will be gone as well.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • rivercreekoceanrivercreekocean Global Mapper User Posts: 4
    edited February 2013
    Thanks, I'm pretty sure that did it! I have just a couple concerns: if I don't use "mark original areas as deleted," I am unable to select the original polygon; is it still there, just not able to be selected? I'm assuming I should delete it (I only want the new polygons). If I select it, in the overlay control center, it says "-2034165 features, 2054448 deleted," not sure why it says I have a negative amount of features.

    Also, I get an error message, "One or more of the areas being cropped is invalid and cannot be cropped," but on hitting OK, it just keeps cropping and eventually finishes with what appears to be success. I'm not sure if it's my shapefiles to blame or not. Lastly, I don't understand what it's asking me when, prior to cropping, it asks me what feature layer I should put it in. I want to be able to save just the new river polygons to a new shapefile.

    Sorry if this is a lot of questions, I don't like to leave anything vague.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited February 2013
    What version and build date of Global Mapper do you have? I'm surprised at the negative feature count, just want to make sure you have the latest before I look into that.

    If you choose to 'Mark Original Areas as Deleted' any of the loaded areas that are cropped should be marked deleted. They would no longer draw or be selectable unless you also have the render of deleted features turned on. They would draw gray then and can be selected and undeleted.

    If your goal is to export to a new file, I would set the target layer as a new one, then provide some name for it. Then it will have its own entry in the Control Center and you can easily turn off everything else and then export just those features to a new file.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • rivercreekoceanrivercreekocean Global Mapper User Posts: 4
    edited February 2013
    I'm running v14.0, build 100512 (I'm assuming that's what it means at the top of the window where it says "b100512"). Here's a quick screencap of it:
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited February 2013
    Can you first get the latest release (v14.1.2) from http://www.bluemarblegeo.com/products/global-mapper-download.php and see if that fixes it? I recall this as a problem that should be fixed now.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.bluemarblegeo.com/
  • rivercreekoceanrivercreekocean Global Mapper User Posts: 4
    edited February 2013
    Yeah, I don't get that issue anymore. Thanks for the help, if I have any more issues I'll update.
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