Young Paul wrote:
There are two formulae here -
3 miles per 1000', or 330' per mile
and 300' per mile.
Both are very easy to use.
The first is about 10% more accurate, if it matters. Which quite honestly it doesn't really.
Full marks for thinking about the accuracy but the true figure is almost slap bang between the two:
For a 3 degree glidepath, the height is 6080ft * sin (3 degrees) per nautical mile from the touchdown point, which is 318 ft/nm.
As you say, I don't think the difference between any of these is likely to be of operational significance.