Viewshed multiple points and attributes not working as expected

bsmavollanbsmavollan Global Mapper UserPosts: 5

I'm currently testing GM 21 and the viewshed tool. I have loaded DEM files for my country and I'm using the viewshed to find blindspots for radars  all over the country.

I can not get it to work as intended with selecting all radar sites in one and executing the tool.
I have set attributes for all sites for sensor elevation and radius, but the program won't aknowledge the altitude as above sea level.
I've tried the following versions of attributes:
TRANSMITTER_HEIGHT - 1234.0 ft above sea level
OFFSETA - 1234.0 ft
OFFSETA - 1234.0 ft above sea level
OFFSETA_MSL - 1234.0 ft
OFFSETA_MSL - 1234.0 ft above sea level

No matter what I try it stills reverts to above ground when generating the viewsheds. And even though if I set the transmitter elevation to above sea level in the dialog it still doesn't change in the resulting viewsheds since there apparently already is a attribute present.

The reciever height  turns out ok all over when setting it to XXX feet sea level in the dialog, as this is the same for all sites per viewshed, but all sensors have a different altitude above sea level based on their location.

So for now I'm stuck with creating the viewshed per sensor.

BTW, great to see the speed highly improved from previous versions.


  • bsmavollanbsmavollan Global Mapper User Posts: 5
    Okay, gotten a little bit further.
    If I set the attribute OFFSETA_MS - 1234.0 ft above sea level the attribute is retained when creating viewshed from multiple points, but....
    I get a nonsense TRANSMITTER_HEIGHT_ABOVE_GROUND. It is extremely high. Giving me an antenna height of several thousand feet.

    In order to fix this I just right click and Edit view shed parameters and click OK without changing anything. GM then recalculates and the viewshed is correct with altitudes and all.

  • bmg_bobbmg_bob Global Mapper Programmer Posts: 2,093

    I suggest that you report this directly to Blue Marble Support via email ( Please include a detailed description of your workflow, and sample DEM and transmitter data sets that can reproduce the problem. Thank you.

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