Error in View Sched when using DT1 elevation data at long distances

kirunaabbekirunaabbe Global Mapper UserPosts: 2
edited December 2008 in Technical Support
Hi,

I am trying to calculate the radio coverage from a ground transmitter to an object 20000 m up in fairly mountainous terrain.

I have loaded DTED level 0 elevation data, as well as DTED level 1 for the site of the transmitter (to get better resolution of nearby peaks).

When running View Shed out to 450 km, which is the max limit we can think of flying, I only get "Unknown error calculating view shed". If I lower the distance to below 250 km, it works fine. And when I close the DTED level 1 data, only running level 0 data, it also works fine out to 450 km.

Why is this? Does Global Mapper not work with DTED level 1 data??? Is it too much data to crunch? Or just way to many Bogons in my office?

I am running version 8.03, is this rectified in later versions?


Regards,

/ Mattias

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited December 2008
    Mattias,

    This is just a memory issue. The default resolution at which the view shed is calculated depends on the resolution of the most detailed layer that is loaded. So if you have DTED1 data loaded the required memory for the elevation buffer used during calculation is going to be much higher by default. What I would suggest is loading your DTED1 data, but manually increasing the X and Y sample spacing for the view shed by say 50% to decrease the required memory enough for your full range to work.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • kirunaabbekirunaabbe Global Mapper User Posts: 2
    edited December 2008
    Mike,

    Yep, worked like a charm when increasing sample spacing. I had to increase more than 50%, though less than 100%.
    :)

    Is this memory issue in the programme, or would it disappear if I increased the memory of the computer? In case I would like to use the lower spacing?


    Cheers,

    / Mattias
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited December 2008
    Mattias,

    More than likely you are just hitting the maximum memory size that can be allocated on a 32-bit Windows application, so more memory probably wouldn't help.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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