Confusing passage in U-boat commander's handbook

[Platapus]

I would like someone smart to translate the following in to nice small words I can understand.

From the U-Boat Commander's Handbook section 105 e

In every submarine attack, whether by day or by night, the attempt must be made to obtain reliable data for aiming (controlling) the torpedo, by exhausting all possibilities with care and deliberation (measuring the deflection with the aid of the line (of the horizon), increase the size of the masts at a given height in the 1/16 scale, overhauling as to course and speed, by day and night, on the surface.

That is one hell of a sentence. I realize that this is an English translation from German, and hence there will be some awkwardness. But I am confused at some of the statements.

My questions are

1. What is meant by “ measuring the deflection with the aid of the line (of the horizon)”. Especially the line of the horizon portion.

2. What is ment by “increase the size of the masts at a given height in the 1/16 scale.”