The Digital Golf Range Finder, which costs less than £20, calculates the distance from where you stand to the pin by using trigonometric calculations, or something. Anyway, because it knows the height of the flag, the Range Finder can then calculate your distance from the flag according to how small it appears in the range finder.
With a range of about 460 foot it should be useful at the local pitch and putt, at the very least. We suppose, although, haven’t tested it (yet) that it could be used for calculating artillery fire and the like during a water fight. Regardless of secondary uses, though, you’ll never have to guess how far away the hole lies and you won’t have any excuses for landing short or over hitting it.