Radar designation of JDAM targets - hit and miss?

[doedkoett]

I have been playing around with the new JDAMs and I have noticed that bombs given their designation from the radar sometimes miss. Me and a friend tried to bomb four targets with four GBU-31's yesterday, and we designated the targets using the AG-radar. Out of four bombs only three were dropped as my wingman had the bug where the bomb disappears from the smart weapons page. All three bombs missed with quite a wide margin.

The mission date is set sometime in 1995, so GPS should be active, and thus also EGI which should take care of any INS drift, right? Are we doing anything wrong perhaps, or does the radar lack enough precision for this kind of work, or do the JDAM´s need a bit more polish from Razbam?

[Ramsay]

1 hour ago, doedkoett said:

Are we doing anything wrong perhaps ...

Without a track or video - it's hard to know.

Take a look at this GR video and see if you spot anything you may have missed (JDAMs are WIP and not all systems/modes are working).

Perhaps recreate your issue in SP and share the track/video to help us, help you.

1 hour ago, doedkoett said:

... does the radar lack enough precision for this kind of work

The radar should be fine.

Edited November 20, 2023 by Ramsay

[doedkoett]

1 hour ago, Ramsay said:

Without a track or video - it's hard to know.

Actually, there is video:

(designation starts about 47 minutes in)

[BigBorner]

Am 20.11.2023 um 12:10 schrieb Ramsay:

Without a track or video - it's hard to know.

Take a look at this GR video and see if you spot anything you may have missed (JDAMs are WIP and not all systems/modes are working).

Perhaps recreate your issue in SP and share the track/video to help us, help you.

The radar should be fine.

 

Hm. Notso repeats over and over again that it is very important that you have the radar slaved to a target point in the vicinity of the to-be-mapped area to get correct terrain elevation for mapping and targeting. 
That’s something that is not happening in this video. Maybe add this to the workflow if someone intends to follow that video. 
 

And WSO can zoom in even more then the pilot by HA Trigger + TDC depress. 

Edited December 15, 2023 by BigBorner

[Ramsay]

33 minutes ago, BigBorner said:

Maybe add this to the workflow if someone intends to follow that video.

The DCS F-15E JDAMs are WIP, the Smart Weapon data block "suggests" that the transferred co-ordinates (Sochi) and altitude (65 ft MSL) match the target location.

As the OP's targets are at 5900ft MSL on the Nevada map - I'll need to test in SP to see if there is a guidance or HAT issue there.

[BigBorner]

vor 2 Minuten schrieb Ramsay:

The DCS F-15E JDAMs are WIP, the Smart Weapon data block "suggests" that the transferred co-ordinates (Sochi) and altitude (65 ft MSL) match the target location.

As the OP's targets are at 5900ft MSL on the Nevada map - I'll need to test in SP to see if there is a guidance or HAT issue there.

I’m just repeating what Razbams SME is saying about it. 
 

I mean, 65ft isn’t a big difference (he also says that MSL will be used as reference in SP) - maybe it only becomes really relevant in case differences are bigger.  

[Ignition]

5 hours ago, doedkoett said:

I have been playing around with the new JDAMs and I have noticed that bombs given their designation from the radar sometimes miss. Me and a friend tried to bomb four targets with four GBU-31's yesterday, and we designated the targets using the AG-radar. Out of four bombs only three were dropped as my wingman had the bug where the bomb disappears from the smart weapons page. All three bombs missed with quite a wide margin.

The mission date is set sometime in 1995, so GPS should be active, and thus also EGI which should take care of any INS drift, right? Are we doing anything wrong perhaps, or does the radar lack enough precision for this kind of work, or do the JDAM´s need a bit more polish from Razbam?

A WSO friend and me (pilot) attacked 2 ground targets with only radar designation because of weather. 1 EWR (55 type) and 1 antena ( the static, the big antena red and white I think it is). We used 2 GBU-31, both weapons destroyed their target.

We knew the general location so we had a waypoint nearby for altitude.

[BigBorner]

vor 17 Minuten schrieb Ignition:

A WSO friend and me (pilot) attacked 2 ground targets with only radar designation because of weather.

By having the WSO create the Target Designation and Pilot uploading them to the weapons via SmartPacs?

 

 

[Ignition]

8 minutes ago, BigBorner said:

By having the WSO create the Target Designation and Pilot uploading them to the weapons via SmartPacs?

 

 

Yes

[Rainmaker]

8 hours ago, doedkoett said:

I have been playing around with the new JDAMs and I have noticed that bombs given their designation from the radar sometimes miss. Me and a friend tried to bomb four targets with four GBU-31's yesterday, and we designated the targets using the AG-radar. Out of four bombs only three were dropped as my wingman had the bug where the bomb disappears from the smart weapons page. All three bombs missed with quite a wide margin.

The mission date is set sometime in 1995, so GPS should be active, and thus also EGI which should take care of any INS drift, right? Are we doing anything wrong perhaps, or does the radar lack enough precision for this kind of work, or do the JDAM´s need a bit more polish from Razbam?

GPS should not be active in a ‘95 mission for one, so the jet is INS only. I believe the date the Zeus set is for ‘98 or ‘99. For 2, radar is inherently problematic if trying to target for JDAM for multiple reasons. 

Edited November 20, 2023 by Rainmaker

[Ramsay]

12 minutes ago, Rainmaker said:

GPS should not be active in a ‘95 mission for one, so the jet is INS only. I believe the date the Zeus set is for ‘98 or ‘99.

The "general" date for GPS to function in DCS i.e. F/A-18C, etc. is March 24th 1994, IIRC the date of the last satellite.

However, as you say and confirmed in the DCS F-15E Manual on page 271

Quote

NOTE: EGI will not be available for missions set prior to 1998, in which case only INS / MN will work

 So although there will be GPS for the JDAM to function, the INS of the aircraft "may" have an element of drift - time to test different mission dates I think.

[doedkoett]

2 hours ago, Ramsay said:

 So although there will be GPS for the JDAM to function, the INS of the aircraft "may" have an element of drift - time to test different mission dates I think.

That could have been the culprit - the bombs went where we told them, but but we simply gave them bad data due to drift. I´ll have to check that out.

[BigBorner]

vor 13 Stunden schrieb Rainmaker:

For 2, radar is inherently problematic if trying to target for JDAM for multiple reasons. 

So were not really supposed to use it for that? Or what’s the consequence of that information? 

[Rainmaker]

8 hours ago, BigBorner said:

So were not really supposed to use it for that? Or what’s the consequence of that information? 

It can be used, it’s just not going to be as point and shoot as people want it to be.  Positional/altitude errors are going to be a thing unless people are through on their mission planning, etc.  It has its limits on both its accuracy depending on how its used but also just in the ability to be able to accurately place the cursors exactly where needed.  I feel like people’s issues will stem more from user errors than anything as they try to do things with it for which it was not intended. 

[Nealius]

Cursor placement is a huge one for me in my experience so far. Dropping GBU-38s on trucks designated by radar varies from 33% to 80% accuracy. But for larger targets and larger bombs, e.g. SA-2 sites, GBU-31s, accuracy is pretty damn good.

[BigBorner]

vor 19 Stunden schrieb Rainmaker:

to be able to accurately place the cursors exactly where needed.

Yeah, that’s for me the biggest headache so far and attributed most misses to it. 

Can’t say anything on the technical limitations on coordinate precision from a radar designation in dcs - but I was hoping I was the only error factor there  

[doedkoett]

Well, I think I can confirm that my problem was GPS-related. I made a quick mockup of the mission I played, ran it twice - once with the year set to 1995, and the second time I set the year to 2020. The first time the bombs landed in a neat rectangle, just a little bit offset from the actual targets. The second time they were spot on. So I guess that mystery is solved.

I guess since I can´t blame the module, I will have to be mature enough to blame my friend who made the mission that set me up to failure. 

Edited November 23, 2023 by doedkoett

[Deano87]

Gyro drift is a killer!

[Tenkom]

Wouldn't an A-G radar designation be a point relative to the aircraft? And if so, as long as the bomb is dropped shortly after said designation, wouldn't the bomb go to that relative location? Assuming the bomb and plane have the same coordinates when you drop the bomb?

i.e. It doesn't matter where the plane thinks it is if it knows that the target is x meters north and y meters east of where the plane is and you tell the bomb to go x meters north and y meters east it will hit the target.

I am probably completely wrong here but that's how I thought it would work, especially when there is no GPS and it's all inertial navigation.
 

[doedkoett]

No, the bomb will go to the map coordinates you give it, either by entering them manually, or from the mission planning tool or by designating it with the onboard sensors. The onboard sensors know where they are looking because they know where the aircraft is. However, if the nav system is off, for example 100 m west and 200 south of where it think it is, the coordinates will be correspondingly wrong - instead of the correct coordinates, the coordinates you will get are the ones corresponding to a position 100 m west and 200 m south of the target.

So in a sense, yes, the designated point is a point relative to the aircraft, but it is translated to a point referenced to the earth, and that is where the trouble starts. If the bomb was laser guided, there would be no problem, since that "system" is totally internal to the aircraft. An unguided bomb would work too. But the GPS guided bombs uses an internal source (INS => Radar/TPOD) for getting the destination, and an external source (GPS) to get there.
 

Edited November 24, 2023 by doedkoett

[BigBorner]

vor 18 Minuten schrieb doedkoett:

external source (GPS) to get there.

Which did not exist in the initial mission setup, so I would assume also used INS only and probably introduced also its own drift. Idk if this is modelled for the bombs though 

[doedkoett]

Since the bombs are ED, and ED seems to have their GPS-cutoff in 1994 I believe the bombs did use GPS (mission was in 1995). The precision with which they missed makes me believe they were GPS-guided. They weren't entirely ballistic, because that would not have resulted in the nice, albeit offset hit pattern.

[Tenkom]

On 11/24/2023 at 3:37 PM, doedkoett said:

No, the bomb will go to the map coordinates you give it, either by entering them manually, or from the mission planning tool or by designating it with the onboard sensors. The onboard sensors know where they are looking because they know where the aircraft is. However, if the nav system is off, for example 100 m west and 200 south of where it think it is, the coordinates will be correspondingly wrong - instead of the correct coordinates, the coordinates you will get are the ones corresponding to a position 100 m west and 200 m south of the target.

So in a sense, yes, the designated point is a point relative to the aircraft, but it is translated to a point referenced to the earth, and that is where the trouble starts. If the bomb was laser guided, there would be no problem, since that "system" is totally internal to the aircraft. An unguided bomb would work too. But the GPS guided bombs uses an internal source (INS => Radar/TPOD) for getting the destination, and an external source (GPS) to get there.
 

 

Ok. So if the bombs didn't have gps they would have the same drift as the plane, presumably the plane would supply the bomb with what it thinks is the current position at drop, and would have hit the target?

[doedkoett]

50 minutes ago, Tenkom said:

Ok. So if the bombs didn't have gps they would have the same drift as the plane, presumably the plane would supply the bomb with what it thinks is the current position at drop, and would have hit the target?

Yes, I presume so. IDK if the JDAMs have an INS in game. I mean, GPS jamming is not a thing in DCS, so there is little need for a backup. Haven't tried, but I guess dropping JDAM before 1994 (ie before GPS exists in-game) would just have them go ballistic. But it would be interesting to learn if anybody has tried and seen other results.

[Deano87]

On 11/25/2023 at 5:43 PM, Tenkom said:

Ok. So if the bombs didn't have gps they would have the same drift as the plane, presumably the plane would supply the bomb with what it thinks is the current position at drop, and would have hit the target?

There's no guarantee that the INS in each bomb and the aircraft would drift in the same direction by the same amount so I doubt that would be the case.