Question 156672
it depends on how far away the fire is.
since the ground and the horizontal line of sight are presumed to be parallel (ignoring the curvature of the earth), then that angle is the same as the angle from the site of the fire at ground level to the height of the tower.
if you were to try to estimate distance to the fire and you could measure the angle, and you know the height of the tower, you would take the tangent of the angle to get the distance from the firehouse.
you could use cotangent as well and it would be more direct but my calculator only does tangent.
example:
firehouse tower is 100 feet high.
standing on top of the tower you determine the angle from the horizontal to the point of the fire to be 15 degrees.
once you have that, you take the tangent of 15 degrees = .267949192
then you use the formula:
ground length = height of tower / tangent = 100 / .267949192 = 373 feet.