The stadimeter is not accurate though, either - but not because of the machinery on the sub (usually)... are you aiming correctly, pointed exactly on the top of the mast, or are you maybe a yard above, or perhaps below? What does that yard extrapolate to across a 3,000 yard distance? Is that the mast you are actually seeing??... Is the listed mast height measurement accurate? As RR alludes to, all of the nations altered their ships as a natural "aging" process (alterations for new gear etc), but also, during time of war, they would purposefully alter the look of a ship to make targeting more difficult - on purpose, of course. So, besides the "aimer" (your eye) being off, the mast height might be incorrect, even if you do properly ID a ship... Look at it this way, if you hit at a 50% rate, dud or boomer, you're doing pretty good in my book. Look at all of the "professionals" that were running around back when, and their shooting percentage - excluding a select few, of course...

- the closer you are, the more assured you are of "accuracy", a fleeting term that...