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Old 07-18-2019, 02:58 PM   #111
Harlikwin
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Quote:
Originally Posted by Holbeach View Post
INS/ARBS, is the basis of the system and will calculate a solution without DMT. It is using the ARBS.


With the DMT added, you can see the target, slew the marker and lock on. It adds accuracy, but is not essential for an attack to be performed.


These are the 2 variations of ARBS. INS, diamond. DMT, square.


..
I think we are mostly on the same page, but as I understand it, the ARBS measures the angle rate change based on DMT tracking to get a slant range to target which is used to supply the Height over target (HOT) information to the MC (ballistic computer) which then calculates the delivery solution.

"Range to Target. The primary ranging method is by using ARBS via the DMT. The ARBS, via the DMT, uses target angular motion (in two phases) to kinematically calculate target range and aircraft motion relative to a fixed point in space." (1-197)

also:

"1.10.4.1 Dual Mode Tracker. The dual mode tracker is the heart of the AV-8B's angle rate
bombing set." 1-198


If there is no DMT lock the MC is just simply using the INS target height, and the MC uses whichever "altitude" source and takes the difference to get the HOT, since there is no angle rate change input unless the DMT is tracking something.

"INS designation. Using the INS TD LOS angle and elevation (Baro or RadAlt), the range (Rs) to the target is calculated. This is resolved into the X, Y and Z planes. INS output along the X, Y and Z axis are subtracted from Rs ranges as theaircraft progresses towards the release point predicted from the Runge Kutta output." (1-197)

Also

"1.10.5 ARBS Management. Mode selection is made using the sensor select switch on the control stick. See Figure 1-127. ARBS and INS modes are mutually exclusive."

The diagrams on 2-28 and 2-29 illustrate which components are doing what in these modes.


At any rate what I find interesting about your technique is that with the DMT off, that you can:

a) Designate the target with the CCIP box without the DMT/ARBS

b) How does that actually work without the ARBS/DMT?

c) Does it work like that IRL without the ARBS/DMT?

It makes perfect sense how it works with the ARBS in the loop, you designate, it gets range/HOT and coverts to auto.

But how that works with just the INS is a bit mysterious to me. How does the plane know where the ground is? I understand that based on the INS you know where the plane is in space and where its pointing, and if you draw a ray from that point that intersects the ground you now have point on the ground. But the 1995 era harrier has no way of knowing where the ground actually is and event the 2003-05 era harrier may not either.
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Old 07-18-2019, 03:48 PM   #112
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I have been reading those same paragraphs, over and over and the Game manuals, but find it difficult to come to an absolute certain conclusion.


INS is part of ARBS and can come to a solution without the DMT. It also supplys information to allow the DMT to do its job.
But is it working independantly of ARBS, when doing its own thing?

How can it work when I've turned off the DMT and not selected a sensor? Does it turn it on when the pickle is pressed for CCIP?
What is DMT without video? OK, found that bit.
Sometimes I get INS with video. (not slewable). OK found that bit.


Whatever mode I use, I can get most of the bombs/CBUs in the ring (about the size of Holbeach large target area) from 15000'. Maybe the game has 1 number cruncher for everything.


Back to the manual.
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Old 07-18-2019, 04:37 PM   #113
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So the ARBS/DMT is an integrated system that has nothing to do with the INS, they both provide information to the MC/SMC to do the ballistics calcs.

The DMT can either use TV or Laser tracking information to provide the needed angle track rates to get the range. I would assume it "turns on" when you pickle to create the target point. But you said in your example the DMT was powered off (DMT power switch right?). If thats the case I'd say its a detail razbam missed/bug.

What I found odd and possibly wrong in your example is using the CCIP/Auto conversion to designate a target WITHOUT the ARBS/DMT. I don't "think" that should be possible because to create a targetpoint for the INS, there have to be 2 things it has to know:
#1: where the plane is
#2: the distance and bearing to the target.

Without the DMT/ARBS working it only knows #1

Typically INS bombing will have the known 3d cooridnates already in there so no mystery there.
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Old 07-18-2019, 04:44 PM   #114
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I'm just throwing it out there and it could be completely wrong, but isn't it possible that by knowing a) where the plane is and b) where the CCIP cross is pointing relative to the plane (which will rely on some combination of altitude, speed, heading etc), the computer can calculate distance and bearing to the target?
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Old 07-18-2019, 05:16 PM   #115
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Quote:
Originally Posted by TLTeo View Post
I'm just throwing it out there and it could be completely wrong, but isn't it possible that by knowing a) where the plane is and b) where the CCIP cross is pointing relative to the plane (which will rely on some combination of altitude, speed, heading etc), the computer can calculate distance and bearing to the target?
Yes, providing it knows where the ground is in that case (or height of ground where its pointing). thats the whole question with regard to CCIP mode issues. I'm not sure the harrier NAV/map system we have has that capability (if someone knows for sure point me to it please). Then there is the follow on question as to how accurate that actually is as the whole nav system has spherical error associated with it (lets say 10m RMS if GPS is working right and way worse if not), and then the gyros have errors as would any sort of digital map data which has 100m or maybe 30m resolution (fine for nav, but certainly less accurate for a weapons solution....)
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Old 07-18-2019, 05:30 PM   #116
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Quote:
Originally Posted by Shrike88 View Post
As seen in the video I wish we had the Release tone as well as its discussed in the manual.

Can be heard in the video at 1:40 ish.

I haven't noticed it before, but yes, if it's in the manual, I wonder why we don't have one.
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Old 07-18-2019, 05:37 PM   #117
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If you place a point on a known map height, as soon as you move through space a new angle is produced, which will give a new exact distance to that point. How does that sound?
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Old 07-18-2019, 06:15 PM   #118
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Quote:
Originally Posted by Holbeach View Post
If you place a point on a known map height, as soon as you move through space a new angle is produced, which will give a new exact distance to that point. How does that sound?
..
Yeah thats fine, you don't even have to do that, if you know where 2 points in space are relatively speaking you can calculate the ballistics solution no problem, thats how INS bombing works. The historical and current issue with it is that you generally don't know the planes positions with all that great accuracy (from a weapon delivery standpoint) most of the time. Even with GPS working perfectly you have some (1-15m) error rates, which means... Your bomb lands 1-15m (at best) from the target (ignoring further errors like wind, atmosphere etc).

And my question all this time has been if the harrier actually has a map with known heights on it from this era. I can't really find an answer or reference to the nav system having high res DTED data for this to work in the Tacman. Nor is a solution like this even implied for CCIP or INS bombing in the tac-man whereas things like ARBS are explicitly explained.
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Last edited by Harlikwin; 07-18-2019 at 06:26 PM.
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Old 07-18-2019, 06:38 PM   #119
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In principle, measuring relative motion/position to get a targeting solution and using INS only for aircraft height does sound more accurate but yes, it probably shouldn't be entirely reliable. That feels like an issue across most DCS modules though, not just the Harrier.
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Old 07-18-2019, 07:11 PM   #120
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"INS designation. Using the INS TD LOS angle and elevation (Baro or RadAlt), the range (Rs) to the target is calculated. This is resolved into the X, Y and Z planes. INS output along the X, Y and Z axis are subtracted from Rs ranges as theaircraft progresses towards the release point predicted from the Runge Kutta output."


Doesn't this cover what you want?

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