Procedures for Manual Ranging
Determining target range in manual TDC
by Frank Kulick

(Many thanks to Frank for providing this in depth tutorial on manual ranging - Hondo)

The following procedures can be used to obtain a fairly accurate range on any surface ship. Its use may not give immediate accuracy at long ranges, but experience will refine the process and work well. It is the same method used during WW1, 2 and every time between and after to gain a non-detectable passive range to a contact from a submarine.

First establish how much of the contact is actually visible. This is very important since the Mast head heights established were gained from Full View at periscope depth, IE: waterline to top from 1000 yards. This was done to obtain the most accurate mast head height.

Realize that the farther away a contact is the less you will see of its full view so this will have a great effect on your ability to get an accurate range. Situations of “Hull Down” will present themselves and you just have to look at the silhouettes in ONI-208J and do calculations of how much of the ship you see and go from there. Do not adjust the mast head height number for the contact because of this, just if you only see from his superstructure-up and it’s only .1 div in high power(4X) then that’s what you use. Additionally, the computer graphics throw a serious curve by making the mast disappear at different times. This usually goes away inside of 2500 yards, but adds to the difficulty.

Second, There are only two powers you can take observations with. 1X and 4X. Looking through the Scope and only the scope, decide how many divisions the target takes up. The divisions are divided into three small ticks capped by large ones IE: IiiiIiiiIiiiIiiiI. Disregard the dots on the I’s and that’s what you see. For ranging, Use the VERTICAL set of Tic’s only.

The divisions are divided by 1, IE: 1.1,1.2,1.3,1.4,1.5,1.6,1.7,1.8,1.9. The tics on your boat however line up on .25, .5, and .75. It’s all-ok, just establish how YOU read it, calibrate yourself, and go to war.

Finally, once you figure how many divisions, use the following method to establish range:

For HIGH power (4X) multiply Masthead height by 80 then divide the answer by the divisions. IE: 100ft MHH—100x80=8000 8000 divided by 1.5 divisions = 5333 yards.

For LOW power use 20 vice 80. I use a calculator (it is my electronic weapons officer—he goes along with the game's electronic diving officer!

How to find a target's course

The first thing to do is get the compass planted in your head. The game makes this easier because north on the chart is always on top. I assume you understand that all bearings on the periscope or TBT are relative. The targets course is true, your course is true. Converting Relative bearings to true is a slight pain, so try to deal with True if possible. So what you do is this; Lets say you are on course 045dT (T=True, d=degrees) a contact bears 000dR (R=Relative) and has a Starboard (you see the starboard (right) side of his hull) 90d AOB) (Angle on the Bow) take the reciprocal of 045dT=225dT and for a STBD AOB you subtract the AOB from that reciprocal bearing, which would give you 135dT for target course. That one is easy, now say you are on course 270T, a contact bears 045R with a Port 25d AOB. You take the reciprocal of the TRUE bearing which is 315dT you subtract 180 to get the reciprocal=135 then for Port AOB's you ADD the AOB to the reciprocal= 135+25=160. 160dT is the targets course!

How to find a good launch point

Speed X 100 = distance traveled in three minutes. If you are doing 5 knots, in three minutes you will have traveled 500 yards. A 30knot torpedo will travel 1000 yards in one minute and so on. This can help you put your boat in a good spot with a pair of dividers and the chart using the way-point lines to "mark" the spots. It would be a lot easier if I showed you with an actual game. I used this formula and method a lot in the Yellow Sea with electric torpedo's and a calm sea. I would figure out the impact point, launch point and fire my fish. By the time They hit, I was out of sonar range by 1-2 thousand yards and reloading my tubes! Another formula is distance to track. Track is the "path/Track " the target is on, like a road. If you know the sine table it is another quick way to put you in the right spot to launch your fish. Distance to track= range X sine of the AOB. Example: say a target is 4000yds away, his AOB is a port 25 take the sine of 25=.5 and multiply 4000x.5 and you get 2000. What that means is at that moment and only that moment you are 2000 yds away from his track regardless of what direction you are going. The game does a pretty decent job with AOB simulation, but can be deceiving! I do assure you that having been on submarines, looking out that scope at dawn and dusk, shadows can cause confusion!

Sine’s, Solution adjustments, torpedo spreads

The simplified sine table.

The first numbers are the AOB (angle on the bow), the ones with the decimal point are the simplified sine #'s. Here you go: 25-35=.5, 36-46=.6, 47-57=.7, 58-68=.869-79=.9, all angles greater use 1 . One thing I did to practice AOB and target course was I created a scenario that I practiced with. One of the Guess work I have when refining my solution is target speed. I don't go to the chart to add realism, but my methods must work because I rarely miss. One of the biggest things that will tell you how good your solution is, after you give all the inputs and generate your solution with the red light, watch how closely the TDC's bearing and actual bearing track. Remember a few things, the closer a target is, the faster the bearing will change, if you have a really good range and your bearing and the TDC's bearing do not match, then you adjust the speed you put in the TDC. The Game does a pretty good job on Bow wake, The slower the target is, the less water that gets kicked up at the bow, the faster, more. Also, remember that speed X 100 = distance traveled in three minutes. So distance traveled in three minutes divided by 100 = speed! The formula works in three combinations! Now, one final lesson. There are two ways I use to put in a spread in a multiple salvo situation. First, the only reason to put in a spread is to compensate for any errors in your solution. Also bad torpedoes! But more for solution error. The one method is to use the TDC feature and offset the fish. The other That I use a lot in rush situations is to spread the fish by constant periscope bearings. I watch the target and Line up the cross hairs on the forward mast, hit the spacebar which gives a new bearing input to the TDC, click the red G light and shoot. Then I pick other spots along the targets hull and repeat the procedure of bearing, G light. The bigger the target, the more torpedo's, the more I spread the fish along its hull. It takes a lot of practice to get all this "Mental Gym" down, but with practice you can get it. I hated it at first, but now really dig it!

IJN Mast Head Heights

It took two days and countless hours to “extract” these from the game. There may be some inaccuracies, but none intentional. The little they may be off, is a splash of realism, because The US Navy had data on ships, but not all, and not all was 100% on the nose either! All numbers are in feet.