Originally Posted by
EasternATC
You have mistaken the 45° equation: if you are 1000' AGL, looking down at a 45° angle to a point, you are horizontally 1000' from that point. You have formed an isosceles right triangle.
I only typed what I found in the USAF Manual from low level and VFR flying from the paragraphs to estimate distance. It seemed accurate enough. At 30,000 feet stuff that is a 45 degree angle away is certainly about 30 miles from the aircraft. It certainly isn't 6 miles away. But your geometry does seem correct.
