sonar overlay tutorial (finished, edited)

[greyrider]

hello rosie, happy new year!

im kinda scratching my head , because i don't know what you mean by TMA. but your post brings up a good point. i dont think anyone could play this way every game, even i wont. something like this is only good once and awhile, only when you feel like doing things by the book. until something like this is modded, i wont use it much, because its a pain to build, and can't move with the boat. but every once in a while , ill draw it and have some fun.
but to be a really good sonar operator, its going to take practice,
especially sound intensity ranging. i hope the dev team for sh4 sees this post, so they can come up with something like this for sh4
to be able to do this at the attack map, a stopwatch in every sensor compartment, because after this, i would like to try exploring the possibilities of radar.

[Rosencrantz]

Hello Grey and Happy New Year to you too!

Well, don't hurt yourself. TMA = Target Motion Analyse.

[greyrider]

alright, its finished, except for some editing, i hope it was entertaining, and fun to read. this was like a laboratory
experiment, under ideal conditions, with a target comming into contact with the u-boat at a known range. i think it will be alot harder in real game circumstances, but at least it proves it can be done, with good plotting and good TSD calculations. i'd like to try to make overlays for radar and surface artillery next, i think surface artillery will be a real good challenge to take on. but thats silent hunter III for ya, its like the eveready bunny, it just keeps on going , and going. the best game out there, thank you all for your patience, and a special thanks to the sh3 dev team, you guys showed them how to make a subsim.

[Marhkimov]

Sorry, can I just break in here and go OT for a bit?



Maybe you guys should use the "force"? You know, like Luke did when he turned off his TDC.

Now of course, we shouldn't fully turn off our TDCs, but things are a lot simpler to do when you just guestimate an intercept course, range, aob, and target speed. I do it and I never miss. What's so hard about it?

I don't have anything against rules and techniques. But if there's a simpler way, then maybe it should be explored...



Anyways, I return the floor to you guys.

[Bluewings]

Even if I am well impressed with Greyrider 's work ~as everybody should~ , I go Marhkimov 's "Force" way as it works all the time for me too .

On the other hand , I totally support Greyrider 's request to the SH4 Dev Team about the possibility of many different overlays .

That 's the way to go for the purists ...

Cheers .

[Canovaro]

I have an idea.

If somebody would make sound samples (mp3 or ogg) of screw sounds and put it in the grammophone, then we could compare them to the contacts picked up by the hydrophone and so estimating by sound volume the range of the target.

Maybe a modder could make a second audio player right in the hydrophone room so we could choose the tracks like "sound of merchant at 20 km" or "sound of merchant at 30 km" and then compare them to the contact's sound.

[Rosencrantz]

Ok Marhkimov, ok... We were just having some fun.

And Grey, your idea for tool, it's good. Really.

-RC-

[Etienne]

Radar plotting (Or TMA, if you will) is really, really simple, and described at great lenght in just about any book about collision avoidance, navigation control, or radar. Dutton's Navigation and Pilotting, IIRC has a chapter about plotting. So does Burger's Radar Operator Handbook, Sonnenberg's Radar and Electronic Navigation, and so on.

It's freaking easy, if you can do vectors graphically. First, as you detect the target, mark your position (And, if you want to work with relative vector, trace your course).

Using the range circle, mark the target range. Then, with the protractor, mark the bearing. This is point O (Origin).

While you wait for your next point, we'll trace vector MO (Motion of ownship). Decide over what period of time you'd like to plot - 6, 8, 10, 12, 15 are all popular. Too short, and you'll end up with very small vector. Too long and, well, the target might manoeuver and screw up the plot. 8 or 12 minutes are usually good.

Vector MO has to be the distance traveled by your ship, in the direction travelled by your ship, during the plotting. Imagine that a ship maintaining formation with you will arrive at point O at the end of the plot.

*Deep breath* All good? Ok, I,ll try to rephrase MO again. Suppose you have decided to plot for 12 minutes. (1/5 of an hour, so that's why it's such a popular interval) Your vessel is travelling at 10 knots, course 090. 10 kts / 5 = 2 NM for 12 minutes, bearing 090. Starting from point O, trace a line in the reciprocial heading of your course (270, in this case) and, with the range circle, measure the distance traveled. This is point M.

Note that the game makes this an unnecessary pain in the butt, as the distances on the map are in KILOMETERS.

After half of your plotting interval, (6 minutes for a 12 minutes plotting), mark the target on the chart, using its range and bearing FROM YOUR INITIAL POSITION. This mark is just there to make sure the target is not manoeuvring.

At the end of the interval (IE, 12 minutes after the initial mark), mark the position of the target, relative to your initial position (Point T). Draw a line linking the initial mark (Point O) thru the middle mark and the final mark (Point T) - This is vector OT, Origin To cpa. Continuing this line will give you range and bearing of CPA. (And time, if you bother) The line probably won't go through all the points ; some deviation is to be expected. Use your judgement ; if the spread is too large, the target is manoeuvring. If you used four points (IE, a mark every three minutes for 12 minutes), you'll get a nice curve if the target turned.

Draw a line from point M to point T. This vector is Motion of Target. It represent the true motion of the target - Course and distance travelled in the interval. Vector OT is the relative motion of the target.

To measure AOB, place the protractor reference line on the extension of vector MT, with the angle at point T. Use the other line to connect your initial position.

That's how one does a relative plot. I've just realised that SHIII's gameplay makes a true motion plot much, much easier... If anyone's interested, I can write that up as well, but it's foolishly simple.

[Etienne]

My previous post has the "Historically correct", sort of, method. It's relative plotting.

The easy way to do it, in SHIII, since the chart display is a True Motion Display, is obviously true motion plotting.

Trace your course on the chart, as a reference (This is not strictly necessary, but it will make marking relative bearing easier)

At the beginning of the interval, mark your target's range and bearing on the chart. This is point M. At half the interval, mark the target again. At the end of the interval, mark the target. This is point T. You should also mark your position at the end of the interval, if you want to obtain CPA data.

Add ownship's course and speed (Vector MO) at point M. Remember that it's Motion of Ownship, so from M toward O. Linking O and T gives you the relative vector, the extension of which will give you CPA.

The rest is as explained above.

Should you want to intercept (IE, obtain a CPA of 0), trace a line from T to your position (The one you used as a reference for the CPA). Prolong this line to the other side of T. Place a range circle around point M, whose radius is equal to the lenght of MO. The point where this circle intersect the prolongation of your desired relative movement vector is point O prime. The vector linking M and O is MO prime. The angle North-M-O prime is your course to steer, essentially. Don't forget to add 180 degree if it's west.

Yeah, that's hugely simplified, especially the course-to-intercept part... But taking into account the imprecisions in the games, and the slow speed involved, it'll get you within visual range. Very close visual range.

[greyrider]

just one paragraph was added, on the subject of the target course and angle finder tool, that the bearings given by the course solver are always read as true bearings.

the tutorial is finished now.

thanks rosie, i think you asked me, what if a sound contact is already with in the listening range of the hydrophones.

i just started working on that tonight, and i think i might have something, in a general sense of range to target. my goal is precision, but ill settle for general range at this moment. im looking at two things, sound cones and bearing width, and using the hydrophone ambient noise, as a comparator, in relation to the volume of the screw sounds.
ill write about these subjects tomorrow night, but here is a picture of the sonar cone width, and the ranges the target could be at, at a certain width of the hydrophone sound cone.

[jimmie]

How's it going since then?!

[Dantenoc]

Wonderfull keep it up.

Does anyone know if there is an updated RPM to knot table that includes some of the new ships that appear in the more popular mods?

Yep.....at least for the curious like me......can you write up your findings ?

[mkubani]

Guys, sorry to bump a bit old thread, but anyone got this original tutorial's pictures saved? I don't see them anymore. Is the author of this tutorial still around this forum? Thanks.

[greyrider]

mkubani wrote:

Guys, sorry to bump a bit old thread, but anyone got this original tutorial's pictures saved? I don't see them anymore. Is the author of this tutorial still around this forum? Thanks.

i deleted the pictures to that , but i saved an adobe copy of it, text and pictues, the whole thing, if you would like it, i may be able to send it in an email, if you pm me with your email, address.

if not, ill have to figure out how to get it up to real u-boat simulation, along with an updated sound trainer