Stream Drainage Area from Top

seansullivan84seansullivan84 Global Mapper UserPosts: 3
edited July 2012 in Elevation Data
Hi there,

I want to use the watershed function to get the stream drainage area from the top of the delineated stream. Currently, the watershed function assigns the stream drainage area attribute to the drainage area at the bottom of the stream. This is an issue if you have a small stream (10 sq.km.) leading to a large river (20000 sq.km.) so that the small stream drainage area attribute area is not really correct.

The watershed area corresponding to that specific stream has the proper drainage area so I'm surprised this isn't an option in the generate watershed menu.

Any help is appreciated.

Sean

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2012
    Sean,

    What version are you using? There was an issue that was fixed somewhat recently that caused the combined drainage of all of the areas meeting at a stream end being assigned to the stream drainage attribute rather than just the contribution from that stream, but it should be fixed in the latest release.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • seansullivan84seansullivan84 Global Mapper User Posts: 3
    edited July 2012
    Hi Mike,

    Thanks, I upgraded my version to the latest. The new version addresses the issue with the small stream flowing into the large river however the drainage area is still at the bottom of the stream segment and not the top. Is there any way to get the drainage area at the top of the segment?

    Thanks,

    Sean
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2012
    Sean,

    You could add the flow for all incoming streams, but if it would help I could add an additional attribute that's the flow at the top pretty easily.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • seansullivan84seansullivan84 Global Mapper User Posts: 3
    edited July 2012
    Mike,

    I would appreciate if that could be added. In some cases we are working with 1000 streams in tables and there wouldn't be a good automated way to add upstream stream IDs. Would that be available in the next upgrade then?

    Thanks,

    Sean
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2012
    Sean,

    I can do even better. I made the change right now! Now each stream gets an IN_FLOW attribute with the flow into the start point of the stream (typically sum of MAX_FLOW of all incoming streams, plus maybe a few more for cells in same drainage area that hit start of stream). I also renamed the MAX_FLOW to OUT_FLOW to be consistent with the new attribute. I have placed a new build at http://www.globalmapper.com/global_mapper13.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v13.xx installation folder to give it a try. If you are using the 64-bit v13 version there is a new build at http://www.globalmapper.com/global_mapper13_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

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