Accounting for distance and AOB?

[SubSimTrooper]

Hey all, I have a question that I cannot seem to find an answer to.

When calculating a target's speed (Length-meters / Time-seconds X 1.94), I've found that the results are consistently inaccurate when compared to the speed as listed on the tutorial's map view. Sometimes it's within that golden +/- 0.2kts but most of the time it's not.

So, I've been trying to figure out how to minimize these errors as much as possible.

All that said, and assuming my own speed is 0kts, I was curious if any of you know a way, when calculating the target's speed, to account-for: 1, my own distance from the target; and 2, the target's AOB?

For example, if an 150m tanker, at a 90-degree AOB, takes 50 seconds to cross my reticle from "tip to tip," then the formula-above results in 5.82kts. However, at a further distance, if the same ship with the same AOB take 30 seconds, then the formula spits out 9.7kts (a rather-massive difference of 3.88kts!).

Put another way, my distance from the target and its AOB will-necessarily alter the time it takes to cross my reticle. But, I have no idea how to account for either of these.

I've been searching high and low but have-yet to find (let alone figure out on my own) how this can be done. Thus, any help would be greatly appreciated!

(Edits for grammar and clarity.)