Aob Question

[wolfpack_jim]

Using olec instument (3 omocentric rings) to find distance and AOB i have a problem witch is not significant but i would like to share with you. When the distance is sort < 1000m and degrees from the midlle to the bow of the ship above 20 then the aob seems to be according to the instrument more than 90 witch is falls. In such sort distances it's easy to discern the AOB in an optical way but i wonder if i can do that using the tool. Am i doing something wrong?

[wolfpack_jim]

anyone?

[Rhodes]

Hello, well I remember from the discusstion in the threads, that when the AOB valor is beyond the 90º mark, It' s the range calculation that is wrong. Like, one counts 2 vertical marks and calculate the distance with that valor, but the real one is 2,5, so then the AOB will be off.

I discovered a tutorial that teach us to calculate the AOB (but I can not remember the site, it was one made for SH2) by take 3 bearings at the target, with 4 minutes of interval from wich one. Ex:

B1 - 040
T1 - 12:11

B2 - 037
T2 - 12:15

B3 - 034
T3 - 12:19

Then you calculate two angles: angA= B1-B2 (ex: 040-037= 3) and angB= B1-B3 (040-034= 6)
Now the hard part to explain, you take this valors and use on a formula, that is:

AOB = Tan-11/(1/Tang angA - 2/Tang angB)

AOB = Tan-11/(1/Tang 3 - 2/Tang 6) = 87

The AOB is given by the co-tangent. So with a calculator that formula will give us a AOB of 87º!
Works better in lone ships, convoy's you have to do this in a very good position, with time to take the 3 berings (or more since one will try to sink more than one ship) plus the time to calculate the range and speed.
The advantage is when one use this method, the AOB is no longer an worry, since it is updated along with the bering of the target by the TDC.

[Pisces]

wolfpack_jim:

As Rhodes said, most likely you did the range wrong. Did you put the baseline right on the waterline of the target? And determined the right observed mastheight? Sometimes the masts are so thin the top doesn't get rendered propperly. What was the target. Maybe the mastheight value in the recognition manual was wrong.

Or perhaps the ship wasn't centered anymore when you looked at the mark under the bow because the lock was lost.

The Range/AOB tool is pretty accurate by itself. Any mishaps are due to misuse or faulty input.

Rhodes:

The Sh2 site you mean is probably the link found in my post (link here below).

In that post of mine is also a tool shown (made by somebody else, I have a dowload link provided at the very bottom of it) to solve that complicated formula in the blink of an eye. I hope it helps you. Be mindfull though that this technique is very sensitive to bearing errors. Those 3 and 6 degrees are really too small to depend on the AOB to be accurate. Give it alot more time, or try to get bearings to be more precise. Consider what if the real bearings differences were worst cases: 2.5 and 6.5 (AOB would be 11), or 3.5 and 5.5 (AOB is 168). Thats almost the full 180 degree range.

http://www.subsim.com/radioroom/showthread.php?p=875260#post875260

As a matter of fact, I have created a circular version of this tool with a CAD program, to extend the possible degrees. But I want to expand it further so you can also see the AOB at the last bearing (instead of 1st, which is really simple to do actually, and tactically smarter to have), and can also correct bearing differences for unequal time intervals. Once I have it finnished, would you like to test/try it out?

[Silverleaf]

Pisces,

I'd be willing to help with testing. I'm trying to wrap my brain around all the different tools available for AOB and I'm still lost.

[Rhodes]

@Pisces, yes it was. That spanish site! Yes, you are right:know: , but fortunatly, until this date, the error was not significant. Many times, I use the formula during an surface attack, so the bearing is given by mt WO. Of course, in SH3, they don't give us .X berings, only full numbers.

[Pisces]

Silverleaf: I can understand. All this math behind targeting is indeed like wizardry. It may take a while before it is finnished with the new tool though. If you have any further questions about those AOB mysteries I'm willing to help. Just PM me.


Rhodes: Yes, the crew have the incredible ability of calling out degrees exactly when a target crosses every xxx.5 degree of bearing. This is everything but realistic, but you can use this to your advantage if you like. Count the time between the initial and 2nd bearing with a stopwatch (to the second or so, at minimum I usually wait until the 1st-to-2nd bearing is 5 degrees as that is the lower end of the above mentioned tool-scale) and wait the same amount of time for the 3rd. Then estimate the fraction of the 3rd bearing based on how much time the nearest call-out was before of after the 2nd interval ran out. That works better than just counting the minutes and round degrees. Or, using a 1 degree periscope bearingscale also helps to improve the resolution of the measurements. (And would be more realistic)

[wolfpack_jim]

thanks for your help.
actually what i did wrong was that i counted vertical marks one for one, two for two ets - i counted double only the horizontal marks because i saw this to the OLCGS tutorial. Than i realised that marks have to read in a same way vertical and horizontal. Thanks again you are great and always there:D

[Pisces]

Oh yeah, OLC changed the marks in the 'Gui Special' scope to alow normal mastvalues.