How do you determine AOB without the length of the boat?

[Able72]

The AOB and range errors caused by these two inacuracies only become significant some time after the initail firing solution is calculated.

In other words, as more time passes, the inacuracy introduced by the stadimeter range and AOB calculations beomes greater. Increasing the likelyhood of a miss. So update your range and AOB information often to keep your solution 'close enough' to on target.