Viewshed Non-visible Features

[pathfinder1]

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

[timhoman]

Yes - this feature would definitely be a plus when evaluating LOS requirements for my projects. Thanks for suggesting it.
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[global_mapper]

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

[pathfinder1]

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.

[timhoman]

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_mapper]

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_mapper]

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

[pathfinder1]

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).

[pathfinder1]

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_mapper]

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