the formula for a 3 degree glideslope is 300' per one nautical mile
3 miles, 900feet
it is actually closer to 316 feet per nautical mile.
steeper than 3 degrees would be a little more.
gouge, or little rules of thumb, would get too complicated for a pilot to quickly ,mentally calculate to the Nth degree. But I imagine you can. At TOO great a distance, earth curvature comes into play.
But 300' per nautical mile is close enough. That Asiana Air at KSFO could have used that formula. Or just looking at the visual approach plate you would see that you should be 1900' to 2000' over a convenient landmark
another convenient formula iis to multiply your groundspeed (or airspeed if you have nothing else) by 5 to determine the rate of descent to make good a 3 degree glideslope.
150 knots, your rate of descent should be 750 fpm
get it?