[WIP] Hydrophone Tracker/Quick Plotter

[kylania]

Originally Posted by Pisces

Yes, small bearing changes/short intervals only make bad results. And many bad results do not average to a good one.

It's difficult to explain why. Your measurement accuracy cannot be better than 1 degree if you let your crew call out the degrees. Maybe better than 1 degree if you use the periscope bearing scale. But much worse if you have to listen for the sounds on the hydrophone yourself.

That's the problem I ran into. I made a test mission with a ship heading course 118 at 8kts. The first time I ran the numbers I used exactly 15 minute intervals and used the "Report nearest contact".

The numbers he gave me were 333, 340 and 347. This ended up with a target course of 70 degrees! No where near the true course. I asked gutted about it and he pointed out that using 334, 340, 347, a ONE degree difference in one of three bearings and you ended up with 104 degree course. Still wrong, but at least in the right general direction.

Not sure how to get around this really.

[Pisces]

Originally Posted by kylania

That's the problem I ran into. I made a test mission with a ship heading course 118 at 8kts. The first time I ran the numbers I used exactly 15 minute intervals and used the "Report nearest contact".

The numbers he gave me were 333, 340 and 347. This ended up with a target course of 70 degrees! No where near the true course. I asked gutted about it and he pointed out that using 334, 340, 347, a ONE degree difference in one of three bearings and you ended up with 104 degree course. Still wrong, but at least in the right general direction.

Not sure how to get around this really.

The numbers 333, 340 and 347 indicate that bearing 2 is about the bearing that shows an AOB of 90 degrees. Since bearing 1 and bearing 3 are equal degrees from the 2nd one.

Perhaps it's easiest to see if you make this 3 bearing AOB tool (shameless plug ) It does the same thing as doing the 3 bearing drawing in Gutted's tool, ( has to be) except for calculating the angle of and distance to bearing 4. It's just an AOB tool.

http://www.subsim.com/radioroom/showthread.php?t=147719

Notice how the smaller bearing differences are wider apart(i.e. 5 to 6 on outside scale), compared to the larger bearing differences (i.e. 20 to 21 on the same outside scale). This means the top disk needs to turn less if you want to see how big an effect one degree error has on long interval bearing changes.

[gutted]

Ok after a bit of hacking on the test version of the tracker...


I get this when using the example in the PDF... cant figure out why it's off:


Are we sure the solution in the PDF is correct? Mine was done mathematically with floating point precision and not drawn by hand.

Note: the above UI will not be the final version.. its just the previous version hacked to work with 2 groups of bearings.

[gutted]

If anyone wants to try out the moving version:
http://www.subsim.com/radioroom/down...o=file&id=1704

Be warned its had very little testing, and i'm not yet certain if the results are correct.

It's a beta version that needs testing.

And yes i know the UI is a bit strict (.ie forcing you to start over if you screw up), but thats because this is a very early version and im forcing the user to do things correctly.

Once its working as intended i'll free up the UI and make it more friendly by accounting for changes in data.

[gutted]

Just tried the moving version on a target that was doing 90 degrees at 9kts.

I came up with 108 degrees at 8kts using 10 minute intervals. Not bad accuracy for such short time span.

Only problem? It took so long to freaking do two sets that he was already in view when i started doing the second set LOL. I started using the scope for the bearings.

Will have to not use the moving method when the target starts so close.

[gutted]

Now that i think about it.. im not even sure how practical the 2-leg moving method is given the short hydrophone ranges on a u-boat.

It's rather pointless to be listening that long.

If you look at that example in the pdf the target was like 68nm away.. thats like 125km. Much more practical.

Now scale that down to U-boat a hydrophone of like 20km listening distance. You run for 30 minutes listenging at 3kts for a target thats doing 11kts... and he's already travelled almost half the distance (8km), while you've traveled nearly 3km... and thats just the first leg !!!


It seems much more practical to sit stationary and listen for like 20-30 minutes and see what he's doing before you start moving. If he's closing it wont be long before you get contact anyway. You have about enough time to run to a triangulation point to get his true distance and speed then setup for an intercept.

[jmr]

Yup, manual TMA is a bit of a pain in the ass. I tried it awhile back as detailed in this thread and through examples with Mobo, it ultimately just wasn't worth the time and effort. The concept, however, is really cool - being able to ascertain a target's range, course, and speed through the use of passive sonar. Of course it all goes out the window if the target alters his speed and course I just leave the TMA stuff for the boats in Dangerous Waters and stick to my whiz wheels and Mobo for intercepting known contacts either reported by radio or spotted by my lookout crew.

[Pisces]

Originally Posted by gutted

Ok after a bit of hacking on the test version of the tracker...


I get this when using the example in the PDF... cant figure out why it's off:


Are we sure the solution in the PDF is correct? Mine was done mathematically with floating point precision and not drawn by hand.

Note: the above UI will not be the final version.. its just the previous version hacked to work with 2 groups of bearings.

I too think the results (target course and speed) in the pdf are a bit wrong in that chart. I get a target speed and course when drawing by hand (177-ish) that is much closer to 180 degrees like your tool. My drawing shows a speed of 10.5 kts. But the method itself works.