Answer
583 ft
Work Step by Step
1. Given angle and adjacent side
$\theta = 30^{\circ}$ and $$a = 1000ft$
2. To find opposite side we use tangent
$\tan 30^{\circ} =\frac{b}{1000} $
$b\approx 577 ft$
3. Do not forget to add up the height of the observer
577+6 = 583 ft