Analysis of information sources in references of the Wikipedia article "Mathematical discussion of rangekeeping" in English language version.
The bearing clock was primarily used within the dumaresq, and it could allow a constant bearing rate to be dialed in ... The range clock's constant speed output went into a differential device called the Spotting Corrector, whose gearing multiplexed it out to three further destinations.
Generally air spot was expected to have little effect at ranges under 20,000 yards, where visual spotting remained supreme. The advantage of air spot increased markedly thereafter. In 1935 the Naval War College estimated that at 29,000 yards air spot would be expected to deliver six times as many hits as observation from spotters aloft.
Mk 8 Radar: Range Accuracy: 15 yards (5 m)
To take another example, the US Battleships of the North Carolina, South Dakota and Iowa classes had main director rangefinders of 25X power with a base length of 26 feet 6 inches (8.0772 m)... For example, to find the error at 20,000 m, simply multiply 0.97 m by 20,000 / 2,000 = 9.7 m.
If the target's length is known as well as the present range, the operator measures apparent length of the ship in the form of a bearing measurement (using the stern as the reference point). The formula is: inclinometer angle = L × Cos Ø / R, where: L is the length of ship, Ø is target angle and R is present range.
Generally air spot was expected to have little effect at ranges under 20,000 yards, where visual spotting remained supreme. The advantage of air spot increased markedly thereafter. In 1935 the Naval War College estimated that at 29,000 yards air spot would be expected to deliver six times as many hits as observation from spotters aloft.