To merge or not Merge?

[hachiman]

Do you always merge contacts?
If one of you arrays has a solid track is'nt it easier to just work out the TMA using this?
Trying to stack the dots can be a bit of a pain(At least for me) on a merged contact.
So am i best just using one of the arrays for TMA?

Thanx

[OKO]

If you can merge SA & TA, you will find sooner the solution.

You will need only 3 clean LOBs to have a top solution, so less than 5 minutes if you already tracked the contact for some time, or less than 7 minutes if you just picked him up.

With one track, you need at least 7 LOBs to have an accurate solution.
If you try to make a TMA with one array and only few LOBs, solution will not be unique but multiple, it's a pure waste of time to try to make a TMA before it's the right time to do it.
So, 7 clean LOBs (without any other information sources than SONAR) are needed to work nicely.

That mean if you could merge 2 distant arrays, you better do, because you will have the solution faster.

but it's not very usefull to merge some arrays, if they are to close.
Exemple, merging the conformal and the cylindrical of the KILO isn't very helpfull, neither merging Hull & spherical on a nuke.
These sensors are to close from each others, and you don't have good triangulation with a so small base of your triangle.
result is range determination problems.

About the dot stack :
on a merged contact, dot stack is supposed to be easier to use.
once merged the good tracks (be carefull to merge the same contact ! or your TMA is already dead) you need to record 3 clean LOBs.

clean LOBS => no change of depth / speed / course, and speed above 6 knts during the data record.

once 3 clean LOBS from SA and same from TA are plotted on TMA screen, you just have to put the end of ruler on the 1 cross and the top tick of the ruler on the last cross of LOBs, then you have a very accurate solution.
You don't even need to previously know the speed of the target.

Merging is very powerfull to find quick and very accurate solutions.
but KILO couldn't use that except with UUV (no TA on KILOs)

[LuftWolf]

When I am working in a dense contact environment and I am doing a series of maneovers where I want to hand the contact off to various sensors, I always merge the contact with all of the sensors I want to use so i can more easily find it when I need to regardless of what station I am at.

[Dr.Sid]

With merging contacts from towed and hull sensors you can get quite good solution from only one reading. For short ranges hull+sphere works in similar way.

[Bellman]

In heavy traffic the quicker you merge the SA or Hull and TA contacts, the better and turn to clear that 120 deg
SA baffle and see if anything lurks at distance in the 60 deg prow TA baffle. Mission designers can sneak in
some surprises and they know where to put 'em.

How much and when you turn is a trade-off, as always.

[Henson]

I do TMA for a living, and we fight all the time with a concept called "contact multiplication." Basically, that means if we are tracking the same contact on two separate sonars, the radar, ESM, and visually, and we don't merge all of that data into one single contact, that not only makes our job a lot harder, but it increases the chance that we will lose control of the situation because we are being bombarded with too much information and not effectively using any of it.

Merging that data does several things. As one poster already touched on, it vastly reduces the number of contacts you have to track. Also, more importantly, it combines all of that information so that when you make your TMA solution you are using all of the available data, not just part of it.

If you are able to gain an important contact on two separate sonar sources, DO IT. When you merge those two sonar contacts, you will get bearings and dots for each sonar source. You may have noticed the two dots showing up at the same time on your difference plots. What was giving you fits (not being able to stack those dots) is actually a valuable tool, because if you get those two dots to stack on top of each other, you will know his range. If you look on the geoplot it will be pretty easy to see what is really happening. Your towed array is in a different location than your sperical array, so wherever those two bearings cross become a triangulated point in the water...that is, no kidding, exactly where he was at that point in time. You should see a line of those 'crossed bearings' as time progresses, and by matching those you will have range, course, and speed locked in without doing any work on class (DEMON).

[NastyHyena]

Originally Posted by Dr.Sid

With merging contacts from towed and hull sensors you can get quite good solution from only one reading. For short ranges hull+sphere works in similar way.

At longer ranges hull+sphere is also useful. While you may not get an exact triangulation on the target, it will help localize your solution. Might just mean the difference between plotting your target at 4000 yards heading SE, or 8000 yards heading NW.

[Bellman]

Well LwAmi gives us some nice combos now in heavy traffic, close in which IMO is under 8000 yds.
Try the Quick Missions on hard to see what it means to be thrown into''Spaghetti Junction' or Hyde Park Corner.

[Bellman]

Another good reason to merge SA and TA is, given the more realistic LwAmi 120 deg baffle, if you turn to clear
the SA baffle, and baffle an existing SA sole contact, you will lose your TMA on that contact as the LOBs drop.
The contact remains on Nav but progressively loses accuracy of position relative to truth.
It then takes time to rebuild the TMA unless you turn to re-expose the contact before all LOBs drop.

With a Master, providing you dont baffle both arrays, this loss will not hurt you. Managing turns relative to baffles
requires a little more pre-planning now !