View Shed Analyst Problem

gchamm
gchamm Global Mapper User
edited April 2008 in Technical Support
1.I have load elevation files.
2.Over laid Geotiffs
3.Textured the map.
4.Did the analyst.
5.Tower is in the right position.
6. But no analyst overlay.
What am I doing wrong?

Comments

  • global_mapper
    global_mapper Administrator
    edited April 2008
    What parameters did you specify for your view shed? Is there valid elevation data available at the tower location? If you select the tower point with the Feature Info tool, what attribute values does it list?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • gchamm
    gchamm Global Mapper User
    edited April 2008
    Name=Whitehorse
    Feature Type=Tower
    Geometry=Point location: 494995.493 6732176.427 (Lat/Lon: 60° 43' 30.51" N, 135° 05' 30.25" W)
    Map Name=Whitehorse
    Description=VIEW SHED TRANSMITTER LOCATION
    RADIUS=13.9 mi
    TRANSMITTER_HEIGHT=2299.0 ft above sea level
    RECEIVER_HEIGHT=40.0 ft above ground
    PERCENT_VISIBLE=0.0%
  • global_mapper
    global_mapper Administrator
    edited April 2008
    What is your source of elevation data and what elevation does it have at your transmitter location? It looks like the elevation at that location is around 2100 ft above sea level, which should be fine, although I'm just looking at very low resolution elevation data to get an estimate.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • gchamm
    gchamm Global Mapper User
    edited April 2008
    I am using Canadian DEM Data from GeoBase / GéoBase. The elevation at the tower is 705.301meters which translates to roughly 2299.0 feet.
    I will send you a map of the area and the elevations.
    The map I am using is in .ecw format, is this a problem?
  • global_mapper
    global_mapper Administrator
    edited April 2008
    I get a height of about 2314 ft for 705.3 meters, which would put your tower about 15 feet below the ground, which of course means nothing is visible. Your tower/transmitter height needs to be above the surface elevation for the view shed to be able to see anything, so it would need to be at least 2314 ft above sea level. Typically users specify a height above the ground (i.e. a 100 ft tall tower) rather than an absolute height above sea level.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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