This next bit is from a section of Pigboats called Extra Credit. In it I talk about things perhaps buried in the abstractions of the game. One part is called "What Is My Character Really Doing When..." which explains what is happening in the game world when a character does something - for example:
What Is My Character Really Doing When...
I make a periscope Observation check?
Your character is reaching down to grab the handles of the scope as soon as they clear the well. Snapping them down, you put your face into the hood, and rise with the scope in order to see as soon as the lens clears the surface, minimizing exposure time. If this is a non-shooting observation, you twirl all the way around once at the highest setting first, then again lower, then once more at the horizon in order to look for planes and ships before surfacing.
Getting the Range
If it’s a shooting observation, your assistant will turn the scope to the expected bearing, where the hydrophones or the plot says the target should be. You find the range by splitting the image with a device called the Stadimeter, and bringing the top of one image against the bottom of the other. Then the estimated height of the target is input into the system. This tells you the range by knowing the angle and the opposite side. You also estimate the target's "Angle on the Bow", the angle made by the target's bow to the viewpoint, for example a ship heading exactly asoss the scope from left to right would have an "Angle on the Bow" of port 90. A ship headed right to you would have an Angle on the Bow" of zero. The longer you leave your scope up, the better the chance the enemy will spot it.
You can give a decent shot at estimating the height of a ship’s masts because the Office of Naval Intelligence (ONI) has given you two books - ONI 221, which covers warships, and ONI 208-J, which covers Japanese merchant ships. These books use a classification method which uses the positions of funnels, deckhouses, turrets, masts, and other structures, and the shapes of bow and stern, to identify the class of ship, if not the actual ship itself. This will tell you the tonnage and masthead height.
Paths Not Taken
I was originally going to use the ONI books and make the PCs identify the ship class using them, but I didn’t want to either copy the whole books - they are public domain - or make the group purchase them, so abstracted the whole process.