cacluating ship speed manually

[I'm goin' down]

I do not want to use the 3 minute rule. Plus, I am playing OM and using meters to calculate distances. I found this online, posted by our very own donreed1. I want to calculate speed by timing the target as it passes the perpendicular line on the scope. Will it work?

Ship's length past the vertical graticule / seconds x (3600/1852) = speed.

The bearing to your submarine from the targeted ship, your AOB, must be between 60 and 120 degrees. You should be at full stop for best results.

don1reed provided a quick example: i.e., T2 = 152.7m / 40 sec. x 1.94 = 7.4 kts.

Is this acciurate? Why 3600/1852?

[Diopos]

3600 seconds in an hour
1852 meters in a nautical mile

.

[TorpX]

The formula quoted is accurate as far as it goes, but does not take into account your subs movement. If you want to estimate speed while moving you must account for both your own speed and the relative bearing.


I used to use the following formula:

speed (kts.) = .59 target length (ft.) / time(sec.) + sub speed(kts.) * sin target bearing

if your sub and target are going in opposite directions then the last term sub speed(kts.) * sin target bearing is subtracted.

[Armistead]

I guess....

[TorpX]

Originally Posted by Armistead

I guess....

I guess not everybody likes math.


Actually, I decided that the best way was to just plot it out like they did in real life.

[I'm goin' down]

in OM you can calculate speed using the Kiub interface, but you still have time the target as it passes the perpendicular line on the scope. Using donreed1's method if you are stopped skips the step with the interface. Also, in OM, the U-Boat's don't pick up the target map contact at great distance. If the target is close, saving time in the Kiub set up for manual targeting can be invaluable, especially if the target is moving at a high rate of speed.

[I'm goin' down]

Originally Posted by TorpX

The formula quoted is accurate as far as it goes, but does not take into account your subs movement. If you want to estimate speed while moving you must account for both your own speed and the relative bearing.


I used to use the following formula:

speed (kts.) = .59 target length (ft.) / time(sec.) + sub speed(kts.) * sin target bearing

if your sub and target are going in opposite directions then the last term sub speed(kts.) * sin target bearing is subtracted.

Originally Posted by Armistead

I guess....

These math guys are taking over the world. Next thing you know, they will invent computers to use in every day life, connect them together, and start usikng computers to send messages, prepare business plans, solve problems, and heaven forbid, play chess and challenge Bobby Fischer. They may even try using them to send a man to the moon, can you believe that? It's totally nuts!

[makman94]

Originally Posted by TorpX

.......
I used to use the following formula:

speed (kts.) = .59 target length (ft.) / time(sec.) + sub speed(kts.) * sin target bearing

if your sub and target are going in opposite directions then the last term sub speed(kts.) * sin target bearing is subtracted.

Hi TorpX,

.......i believe that this formula is wrong for getting target's speed,TorpX !

the problem is not so simple for been solved by this simple formula.
where did you find this formula written ? before i proceed and explain why this formula is not correct i would like you to explain it more detailed (for example write the formula more clearer or show with a little example how you are using it and getting speed)) becuase ,maybe, i am missing something at the way you have written this formula.


ps: if you can prove the above formula...would be even better.

sorry for being the 'Doupting Thomas' here but this formula is not working, TorpX. and there is no way to make it work becuase you are not considering the target's course (relative to your own course) factor which is a very important factor ! this factor has equal importance with your boat's speed factor (which you are correctly considering) and has ,also, equal importance with the bearing to target factor (which,also, you are correctly considering).

as i said ,is not so easy problem . a good tool that help in situations like this is the back side of attack disc (in case that we don't want to use digital-modern-calculators)

ps: @TorpX : don't feel offended ...i will be huppy if ,at the end, prooved to be me on the wrong side.

[Pisces]

Originally Posted by makman94

Hi TorpX,

.......i believe that this formula is wrong for getting target's speed,TorpX !

the problem is not so simple for been solved by this simple formula.
where did you find this formula written ? before i proceed and explain why this formula is not correct i would like you to explain it more detailed (for example write the formula more clearer or show with a little example how you are using it and getting speed)) becuase ,maybe, i am missing something at the way you have written this formula.

...

I agree, somehow the AOB should be worked into this too. I don't know how exactly though.

[TorpX]

@ makman94 and Pisces:

No offense taken.
You may be right. I dug the formula out of my old papers and have not used it in a long time. I will play around with it and check before I report back. I should have done this anyway.