Viewshed Non-visible Features

pathfinder1pathfinder1 Global Mapper UserPosts: 10
edited April 2009 in Suggestion Box
I would like to be able to get the non-visible area of a viewshed as a feature. I can derrive that by exporiting and manipulating data in another application, but would prefer it be a feature of the viewshed tool in GM. I've seen this asked for one or two times before as a support question, and think it would round out the tool nicely.

Great product, been using it for years. Thanks

Comments

  • timhomantimhoman Global Mapper User Posts: 49Trusted User
    edited April 2009
    Yes - this feature would definitely be a plus when evaluating LOS requirements for my projects. Thanks for suggesting it.
    --
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2009
    You could do this now by generating a range ring of the appropriate radius centered at your view shed location, which should give you a circle area covering the entire view shed. Then, select all of the view shed coverage polygons, then right click and select to add them as holes/islands in an area and choose the range ring area. This should then give you a complex area that only shows up where there is no coverage.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    Your suggested method works fine for what I need, though not so obvious. I'll have to take a closer look at some of those editing tools. Thanks for your help. I still think it would be a good integration with the viewshed tool directly, though.
  • timhomantimhoman Global Mapper User Posts: 49Trusted User
    edited April 2009
    I am using GM 9.03. I've tried Mike's workaround but it seems a bit problematic when working with complex viewsheds, especially with areas that are holes within the viewshed polygons. Also, I am using a DEM that results in the generation of viewsheds with polygons that include the entire DEM cell and therefore extends just slightly beyond the actual radius I specify for the viewshed - thereby causing another problem when using a range ring with the exact same radius.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2009
    I may be able to easily add an option to generate a view shed of the area not covered rather than what is covered without too much trouble. I'll take a look and let you know if I can get that added. It would be in a v10 build though.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2009
    I have completed adding a new option to the view shed generation to generate coverage in hidden rather than visible areas. I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the change for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    Very nice, works as expected. Thanks for adding this! It results in a smoother workflow with more consistant results (the range ring would sometimes leave artifacts at the ring boundary).
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    Mike,

    I am running into an issue with this new build. I'm finding that using vector obstructions no longer works properly. I'm getting visible area coverage within obstructed areas. This does not occur when I run GM with the 10.2.10.0 executable.

    Steve
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2009
    Steve,

    It actually should be possible to get coverage on top of obstruction areas, this was incorrectly implemented before. For example if you have a obstruction area with a height of say 10m (like a building), before GM would never indicate coverage on top of the area, whereas now it will check whether the transmitter is visible on top of the area and mark it as visible if it is, which seems to be the proper way to things. Everything beyond the area will still be treated the same with the area as an obstruction.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    Mike,

    I think that it worked properly before, at least for our purposes. We're working primarily with vegetation coverage. For visual impact purposes, areas within the vegetation zones are always considered non-visible, so are left out of the viewshed coverage.

    To include areas within the vegetation obstruction would be saying that target object is visible at the top of the tree canopy. That may be so, but we're only concerned with what happens at eye level above the ground.

    I'd have to strongly recommend that either the user has control over this behavior or the old method be used. If visibility shows up in obstructed areas we'll have to discontinue our migration from our in-house viewshed program to GM, unfortunately.

    I'd be happy to discuss further in this forum or via the phone if that would help.

    Steve
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    On another related topic, I'm noticing that with the new build, feature information shows PERECENT_VISIBLE data for NonVisible features as opposed to PERCENT_NONVISIBLE
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2009
    Steve,

    I can see what you are saying. I have made the obstruction area behavior configurable on the view shed dialog so that now you can control the behavior. I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the change for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    I also added a PERCENT_HIDDEN attribute when showing hidden coverage and made the PERCENT_VISIBLE attribute correctly reflect the visible coverage.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    Mike,

    I've tested this build and performed some QA/QC against our internal application and am happy with the results. I'm glad you chose to add the "obstruction area always hidden" as a toggle, giving users the flexibility of both options depending on their circumstances.

    One last thing I've noticed is it seems that when I chose to display hidden areas the PERCENT_VISIBLE and PERCENT_HIDDEN values are switched.

    Thanks so much for your incredible responsiveness regarding these features. They are important to our workflow. Had we been dealing with some of our other unnamed software vendors we could have had to wait years for this kind of service. I'm sure we'll be adding to our license pool in the coming months.

    Steve
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2009
    Steve,

    That's a big advantage of using Global Mapper, you often get updates within hours or days rather than years (if ever!) with other companies.

    I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the PERCENT_VISIBLE and PERCENT_HIDDEN values corrected for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • pathfinder1pathfinder1 Global Mapper User Posts: 10
    edited April 2009
    Perfect. Thanks again
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