Visibility calculations

Question

Hi, I wonder if it is possible to calculate the visibility of a flashing obstruction light on the top a wind turbine, given that there is a shield below the lamp that prevents emission of light at certain angles (for example 20 degrees to each side of the bottom of the light source, see attached drawing)? If the light was emitted in all directions, this would be an easy task. But it is possible to add conditions like this, and in case the answer is yes: How? Thanks in advance for any hints and tips!

Visibility.pdf

DanPatterson_Retired · Answer

so effectively you have a barrier in front of it.  You could specify an appropriate vertical angle range as shown in the

help topic for Visibility...consider a limiting vertical angle of 45 degrees from the ground surface... at somdistance from a 100m tower, you would be able to see the top of the tower... at some point, as you move closer, that vertical 45 degree angle will intersect with the top of the tower... you move closer, and you can't see the top

KjetilMork · Answer

Hi Dan! The big question here is from where (on the ground) will you be able to see the flashing obstruction light? If there is a shield directly below the light source, you will not be able to see the flashing light if you're standing on the ground near the wind turbine (because the shield is between you and the light source). If you walk further away from the wind turbine, you will see the flashing light since it is no longer covered by the shield (as I've tried to indicate on the drawing). In addition to the shield, the terrain will of course also influence on where the flashing light will be visibel or not. So I wonder if it is possible to calculate where the flashing light will be visible based on 1) the terrain and 2) the angle of the light emissions.

DanPatterson_Retired · Answer

visibility is based on height, nothing has to be 'seen' in the visual sense of the word, so I am not quite clear on your meaning.  An object is still there and may be visible whether it is shielded from view or not