Global Mapper v24.0

Newby drawing watersheds

BrunoRSW
BrunoRSW Global Mapper User
edited March 2011 in How I use Global Mapper
Hello all,

One more novice, joining in!

I use Global Mapper mostly to draw out watersheds from elevation maps. To goal is to better manager water resources.

Drawing rivers and getting elevation profiles has not been a problem, but drawing out watersheds is a bit more tedious.

I heard of a ''watershed'' function that figures out the watershed draining a any user-specified point (no doubt computing slope gradients). Is this true, or too good to be true?

Thanks, looking forward to contributing with all of you!

Bruno

Comments

  • global_mapper
    global_mapper Administrator
    edited January 2009
    Bruno,

    There is not currently any kind of automatic watershed delineation feature in Global Mapper, but that is something on our todo list. It might show up for the v11 release this summer.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Ken Yeomans - Keyline
    Ken Yeomans - Keyline Global Mapper User
    edited June 2009
    In my work I often have to determine catchment areas to determine stormwater runoff rates and volumes.
    If there is a drainage algorithm, which may be a big if, it would be a good basis from which to work. Bearing in mind that if the surface layer of a landscape is inverted it becomes another landscape. Valleys (draws) become ridge lines and vice-versa. The same with lakes and hills.

    Marking watersheds boundaries is usually more successful if done working upwards. The search is always to find the nearest next high point. If several points are the same height at the same radius then either pick the middle one or expand the radius and check again.
    The tricky parts may be how to process hills especially if with multiple saddles connect to them.
    It would be nice to have the process automated.
  • global_mapper
    global_mapper Administrator
    edited June 2009
    Hopefully when we get a chance to look at the watershed features we will find a nice algorithm to use.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Griffon
    Griffon Global Mapper User Trusted User
    edited February 2010
    Any update to the request for watershed delineation tools? I'm using v.11 - can we hope for an update that will add some of that functionality? Thanks
  • global_mapper
    global_mapper Administrator
    edited February 2010
    It's still on the todo list, but definitely wouldn't show up before v12 this summer.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Griffon
    Griffon Global Mapper User Trusted User
    edited September 2010
    I see you've added watershed delineation to the newly released v12 (yeah!). Unfortunately, I can't try it out with the demo, but I most always upgrade anyway. ;)

    Would you be able to describe briefly how it works? Is it based on some published models, like the one behind L-THIA, that you can describe or cite? Thanks!
  • global_mapper
    global_mapper Administrator
    edited September 2010
    There is a brief description in the User's Manual at http://globalmapper.com/helpv12/Help_MenuBarAndToolBar.html#file_menu_generate_watershed. Basically is uses the 8-direction pour point algorithm to determine flow, as well as a lowest adjacent increment algorithm to determine flow in flat areas, and a custom algorithm to try and fill depressions.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Griffon
    Griffon Global Mapper User Trusted User
    edited September 2010
    Looking at the graphic supplied at the user's manual link above, it appears that there is no defining a given outlet for a watershed. Is that correct?
  • global_mapper
    global_mapper Administrator
    edited September 2010
    There isn't a separate point feature created at the outflow for the area, if that is what you mean. However, that could be added pretty easily if you think that would be useful.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Griffon
    Griffon Global Mapper User Trusted User
    edited September 2010
    Not quite. What I'm hoping for is to be able to define an outflow on a stream (or even just a slope) and then have the tool delineate the watershed based on it. Perhaps there are ways to fool it (for instance, if the user can control the hydro layer, cut it off at a certain point), but this still wouldn't help with the non-stream (slope) situation.

    I know this is kind of an oddball request, perhaps counter to how it's usually handled, but it comes up from time to time. Actually, all the time for me.
  • global_mapper
    global_mapper Administrator
    edited September 2010
    Actually that is something we are planning on adding soon to the watershed tool as it's not very difficult now that the base functionality is there.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Griffon
    Griffon Global Mapper User Trusted User
    edited September 2010
    Perhaps for an interim release then? Great! I hope it's soon. :)
  • global_mapper
    global_mapper Administrator
    edited September 2010
    Oh yeah it would be available as an interim build. Heck I might even add it in the next week!

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • global_mapper
    global_mapper Administrator
    edited September 2010
    I have completed updating the watershed generation to allow the calculation of the watershed area above any point selected in the Digitizer Tool as well as showing the flow from any selected point as part of the watershed calculation process. I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with the change for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Mark V
    Mark V Global Mapper User
    edited March 2011
    It would be really handy to be able to determine the size of a watershed/catchment at anypoint within a catchment. For example I need to be able to work out how large a catchment is for a given stream to determine what sort of management requirements are needed which is based on the size of a catchment. So if I can work out how big the catchment is at point X and then move further 'up stream' and determine the size of the catchment at point Y (theoretically smaller than point X) that would be great I'm sure it would have plenty of application, thanks Cheers Mark
  • global_mapper
    global_mapper Administrator
    edited March 2011
    I think the option to 'Create Watershed Areas Showing Drainage to Selected Point(s)' when calculating a watershed would work for this wouldn't it? With this you can select one or more point features and have areas created that show all parts of the area of interest that drain to that point.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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