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JDAM feature questions?


Furiz
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19 hours ago, Frederf said:

Thousandths of a minute of arc is about 2m precision already. You can't enter anything better unless we get 10 digit MGRS later. You can also use the GM FCR to employ JDAM through weather.

Can you elaborate on the 10digit MGRS? All i can find is 8 digits, 4 on each axis up to 10m of accuracy.

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MGRS is a scalable coordinate system. Depending on what is specified different levels of precision are possible from the plain GZD to 100km to 10km to 1km to 100m to 10m to 1m. In DCS the native format is 8 digit (10m) precision display in the UI but that doesn't preclude using other levels. As far as I know there has been no practical use for 12, 14, 16, etc. digits but they'd be valid concepts just as valid as 8, 6, 4, 2, and 0 digit.

 

4QFJ 12345 67890

By removing characters from smallest to biggest you can convert from more to less precise designations. "You are cleared to engage targets in 4QFJ" is a valid thing to hear.

 

This 2007 OFP 4.3 F-16CM is certainly capable of 8-digit MGRS entry. What I don't know and really doubt is if it's 10 digit capable. The only reason I think it might have it is because JDAM blind BOC capability is generally not allowed on 8 digit. The precision of the designation is on the same order as the weapon itself.  Dropping on coordinates is usually disallowed on any MGRS worse than 10 digit. That way the precision of the designation is negligible compared to the CEP of the weapon. So when a USAF/USN/USMC airplane has both JDAM and MGRS capability there is a strong motivation to push through a software update that allows 10 digit locations for blind delivery. On the other hand Link 16 has the ability to pass locations digitally which may allow precise attack without such update.

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On 6/13/2021 at 8:00 PM, ebabil said:

 

So we can not send the jdams right to the coordinates like we do with the hornet? 

 

Haven't tried it yet, but as a workaround I suppose you could use the TGP to find target coordinates, and then manually add steerpoints using those coordinates as target points. Obviously it'll be a slow process, and not ideal if it means loitering in unfriendly airspace while you get it all set up, but I don't see another way to accurately drop right now. 

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2 minutes ago, frostycab said:

 

Haven't tried it yet, but as a workaround I suppose you could use the TGP to find target coordinates, and then manually add steerpoints using those coordinates as target points. Obviously it'll be a slow process, and not ideal if it means loitering in unfriendly airspace while you get it all set up, but I don't see another way to accurately drop right now. 

 

Why would I need to get its coordinates after I lock it via TGP? It should work with tgp spi either

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1 hour ago, frostycab said:

 

Haven't tried it yet, but as a workaround I suppose you could use the TGP to find target coordinates, and then manually add steerpoints using those coordinates as target points. Obviously it'll be a slow process, and not ideal if it means loitering in unfriendly airspace while you get it all set up, but I don't see another way to accurately drop right now. 

 

8 minutes ago, smire666 said:

Yep, our goal is being able to make a pinpoint strike without TGP.

 

I still don't get it.

 

How do you obtain coordinates to input in the Hornet? If you have the coordinates, then create a new steerpoint in the Viper and use it to deliver the JDAMs. No TGP needed.

 

If you have multiple targets, then create multiple steerpoints, then at the delivery moment just cycle through them and pickle.

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1 hour ago, ebabil said:

 

Why would I need to get its coordinates after I lock it via TGP? It should work with tgp spi either

The TGP method wouldn't necessarily allow multiple drops on a single pass.  

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What’s weird is the single MK82 (500 lb) bomb almost has a half mile blast and shrapnel radius but I don’t see it in the OB version of DCS

You almost have to hit the target to be effective weird


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Don’t get me started on a MK 84 (2000 lb) bomb

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You can absolutely target a JDAM in the F-16 without any sensor like radar or TGP. If you know the coordinates you type them in as a destination and just make sure that steerpoint is SPI during release. That's still not as capable as the F/A-18 which can specify coordinates directly to each weapon which can then release multiple individualized weapon missions with a single button press. But it's not that much less capable in practice, just less automated.

 

If you understand how JDAMs work in the A-10C and the F/A-18... F-16 works like the A-10C.

 

JDAM kills SPI. If you wanted to you could drop four JDAM with four WR presses simply by slewing the TGP to four places, drop-slew-drop-slew-drop-slew-drop. You don't have to work with steerpoints if you don't want to. With mark points the ability to convert TGP to marks and then drop on marks will be much faster than manual entry of coordinates to steerpoints. Steerpoints are the preferred method when preplanning against fixed targets because it's faster and slightly more accurate but TGP, FCR, even visually are all valid methods of aiming JDAM.

 

 

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Im sorry if this has been discussed but its very confusing. Does the JDAM use the steerpoint or targeting pod to hit? I tried it out making a steerpoint first, and using the targeting pod to pinpoint the location but the weapon seems to hit slightly off. So maybe its not hitting exactly where my targeting pod is looking? Is there a way to make it use the targeting pod precisely? 

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Im sorry if this has been discussed but its very confusing. Does the JDAM use the steerpoint or targeting pod to hit? I tried it out making a steerpoint first, and using the targeting pod to pinpoint the location but the weapon seems to hit slightly off. So maybe its not hitting exactly where my targeting pod is looking? Is there a way to make it use the targeting pod precisely? 

It goes off of SPI, did you initiate a point track or area track with the tgp?
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Point/area track makes no difference for TGP location calculation. It's only a tracking mode. TGP has limited precision capabilities at generating locations by optical track only. All it can do is use angle and terrain database to come up with approximate intersection of that ray and surface. Using laser rangefinder improves things.

 

A test which will show this better is if we had ability to make TGP mark points. Then you can look at numbers of mark created and compare them to actual numbers of whatever truck you were tracking. They'll probably be a little off.

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2 hours ago, durka-durka said:

Can someone answer this for me?  Hopefully it hasn't been asked yet.  What is the purpose of the Impact Azimuth setting?  What scenario would I use that?  Thanks.

Conjecture.

 

For example in an urban environment with high rise buildings there might be a certain approach vector you want the bomb to fly to be able to hit the target.

 

Other example is a bunker where you would want to JDAM to hit the door or any other weak point. Terminal ballistics modeling in DCS is simplified afaik so at this stage the door wouldn't be relevant.

 

In both examples you could set the az to 0 and fly the correct angle to the tgt as well. So I assume that the only time you need it is that the aircraft has limitations to it's flight path as well, for whatever reason. 


Edited by Sinclair_76
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You have to be within a certain number of degrees of the desired azimuth angle at release for it to work too.

It just has to do with weaponeering stuff, which isn't anything we have access to determining to any degree of accuracy beyond frag vs blast vs penetration, because we don't have the computer programs that do that.

And, ED doesn't really require anything close to weaponeering because of how the damage models are close -- but maybe someday. For that to happen though, they will have to give us guidelines related to things like how to best kill people vs vehicles vs buildings vs armored stuff.

I'll also say, although you can input the angle down to a degree, the bomb isn't going to be that accurate. There will be a window that it can hit.

I'd focus more on the impact angle than the azimuth angle. Azimuth angle seems more critical for low impact angle deliveries.

This JDAM stuff is a lot of fun. It's been working great -- today we flew a 3 ship in the viper and took our 10 targets after "weaponeering" them as a group. It's neat.

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1 hour ago, TheBigTatanka said:

You have to be within a certain number of degrees of the desired azimuth angle at release for it to work too.

It just has to do with weaponeering stuff, which isn't anything we have access to determining to any degree of accuracy beyond frag vs blast vs penetration, because we don't have the computer programs that do that.

And, ED doesn't really require anything close to weaponeering because of how the damage models are close -- but maybe someday. For that to happen though, they will have to give us guidelines related to things like how to best kill people vs vehicles vs buildings vs armored stuff.

I'll also say, although you can input the angle down to a degree, the bomb isn't going to be that accurate. There will be a window that it can hit.

I'd focus more on the impact angle than the azimuth angle. Azimuth angle seems more critical for low impact angle deliveries.

This JDAM stuff is a lot of fun. It's been working great -- today we flew a 3 ship in the viper and took our 10 targets after "weaponeering" them as a group. It's neat.

Sent from my Pixel 3 XL using Tapatalk
 

 

 

It would be awesome to have a simulator version of the JMEM to proper weaponeer the targets. And if ED could model that in to DCS that would be cherry on the icing on the cake.

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The way it was explained to me in B-1s and current Viper instructors could correct me is that impact azimuth is the angle a bomb will hit a target 

 

Usually the default angle will work but if you want a little more range you can make the impact angle horizontal (AZ=0) and let the explosives do the work

 

Impact Azimuth gives a bomb some armor piercing capabilty to bury itself and explode

 

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I hate JMEM (Weaponeering) back in B-1B Block C you had to JMEM by hand cause the B-1B did not have the computing power in the 90s

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