Modern Single-Observer Range-Finders

Abstract

THIRTY years ago the War Office asked for a rangefinder for field service that would measure ranges to within 4 per cent, at 1000 yards—that is, 40 yards at 1000 yards, or 160 yards at 2000 yards. A single-observer rangefinder of 30 in. base was designed to fulfil these requirements. In 1892 a naval rangefinder was required that would work within an error of 3 per cent at 3000 yards, which is equivalent to 1 per cent, at 1000 yards. This demand was met by a range-finder of 4 ft. 6 in. base. Whereas in 1895 the effective range of naval gunnery was between 2000 and 3000 yards, the effective range in 1904 was 6000 yards. For this service a rangefirtder of 9 ft. base was introduced.