correct as is GBU38 Accuracy

[RPY Variable]

This can't be right. The accuracy or Circular Error Probable (CEP) of the GBU38 is as bad as a dumb bomb. The waypoint is from the editor, exactly in the middle of the tank X Y Z.

https://streamable.com/pi8l3e

F16 GBU38 CEP.trk

Edited February 6 by RPY Variable

[skywalker22]

As far as it goes for me, I used JDAMs quite a lot lately online, and I had 90% success hit, and from very high above. 

Was maybe the tank a moving target? I hope not.

Edited February 6 by skywalker22

[buceador]

" In its most accurate mode, the JDAM system will provide a minimum weapon accuracy CEP of 16 feet (5 m) or less when a GPS signal is available." 

 

https://en.wikipedia.org/wiki/Joint_Direct_Attack_Munition

[BIGNEWY]

Please ensure you are using the laser to get the correct range for the target, this will ensure the CEP is much smaller. 

thank you 

[skywalker22]

2 hours ago, BIGNEWY said:

Please ensure you are using the laser to get the correct range for the target, this will ensure the CEP is much smaller. 

thank you 

Exactly, forgot to say that. But note, Laser is only good to use in clean weather.

[RPY Variable]

7 hours ago, BIGNEWY said:

Please ensure you are using the laser to get the correct range for the target, this will ensure the CEP is much smaller. 

thank you 

Why so fast with the  "correct as it is"? This has no sense.

1) If there were drift between the target and the waypoint, for example 30 meter to the left, the bomb should fall away from the target (+-30m to the left), but with the same CPG. All bomb should fall near each other, because there is an offset, but the bomb accuracy (CPG) shouldn't change. Image attached showing what I mean.

2) The waypoint was in place in the editor, the mission was just started, so there should be no error, and what shows that there is no error is the TGP pointing to the tank, which was CZ, it was not slewed at any time. In this case, it should work as a B2 with preplan waypoints. Is a INS/GPS bomb.

3) They are also very apart in azimuth, so it not a distance (laser) thing.

4) I tried with lase, almost same result. Image attached.
null

F16 GBU38 CEP with Laser.trk

[AstonMartinDBS]

I replayed the track with the same results (4/4 GBU-38 missed).

Then I tried the mission at an altitude of 5k ft and didn't touch the TGP - result: 4/4 GBU-38 missed. After the release of the 4th GBU I used the TGP to observe the target area, as I noticed, that the TGP was lookin' about 10 m offset of the CZ.

There must be something wrong with the coordinates. Please take a closer look.

CA F-16C TGP offset.trk CA F-16C GBU-38.trk

Edited February 6 by AstonMartinDBS

[RPY Variable]

I release there because I was prepared for someone telling me, "you release from very far away and the bomb had poor energy"... nevertheless. They had plenty of flytime.

Based on what has been shown, I don't see any debate.

Next image is Mk-82 dumb bomb release on level CCRP, same altitude, same all. Almost same accuracy as gbu38.

This is nothing new, it has been like this for quite some time now.

Edited February 7 by RPY Variable

[BIGNEWY]

We have asked the team to take a look at the GBU-38 accuracy. 

Please note factors for improved accuracy. 

Ensure GPS is in use
Use Laser for range calculation. 

thanks  
 

[Hobel]

Am 6.2.2024 um 06:31 schrieb RPY Variable:

This can't be right. The accuracy or Circular Error Probable (CEP) of the GBU38 is as bad as a dumb bomb. The waypoint is from the editor, exactly in the middle of the tank X Y Z.

https://streamable.com/pi8l3e

F16 GBU38 CEP.trk 173.58 kB · 8 Downloads

 

With which airplane were the gbu38 dropped?

it is very important to know that

[BIGNEWY]

I have moved this thread to the weapons section as we are seeing similar issues with the A-10C and F-16C, however the F/A-18C is within expected CEP

thanks

[Lord Vader]

Hello all

After we reviewed the tracks and observed the conditions, we believe we have found the culprit for your reports.

It's actually a feature in DCS, regarding GPS quality.

In your track @RPY Variable your F-16C is set to the Red Coalition. As such, the GPS quality is by default much lower than the Blue Coalition. In order to mitigate this, you can select "unrestricted sat nav" option in the Mission Editor or just select a Blue coalition side. 

I tested this myself with the DCS: F-16C Viper and with the DCS: A-10C II Warthog and you can observe the difference. 

Without proper or with poor GPS guidance, the GBU-38 can have a CEP at about 30m or even more. So this is actually well modelled.

Thank you for your patience and, yes, this was a tricky one. 

[Exorcet]

8 minutes ago, Lord Vader said:

Hello all

After review the tracks and observing the conditions, we believe we have found the culprit for your reports. It's actually a feature in DCS, regarding GPS quality.

In your track @RPY Variable your F-16C is set to the Red Coalition. As such, the GPS quality is by default much lower than the Blue Coalition. In order to mitigate this, you can select "unrestricted sat nav" option in the Mission Editor or just select a Blue coalition side.

Would it be possible to move this option, and any related options to a coalition configuration menu? That might make it more obvious, and also allow customization of sides instead of relying on a preset notion of which coalition represents what.

Edited February 7 by Exorcet

[Lord Vader]

6 minutes ago, Exorcet said:

Would it be possible to move this option, and any related options to a coalition configuration menu? That might make it more obvious, and also allow customization of sides instead of relying on a preset notion of which coalition represents what.

I'm not sure what you mean. This is already in the mission options to restrict the use to the Blue side (unchecked) or allow it to all coalitions (checked).
What would be your suggestion? 

null

[Exorcet]

1 minute ago, Lord Vader said:

I'm not sure what you mean. This is already in the mission options to restrict the use to the Blue side (unchecked) or allow it to all coalitions (checked).
What would be your suggestion?

The current option seems to be built around Blue with the assumption that Blue will always have optimum GPS while any other coalition may or may not.

If the option was separate from Blue and could be applied independently to any coalition, that would add the following new possibilities:

-Blue with degraded GPS

-Non Blue with optimum GPS while Blue has degraded GPS

-Better support for more coalition if added in the future

I think it would also be a little more intuitive form of the GUI.

Here is a rough edit of your image showing what it might look like:

[Lord Vader]

Oh, I see. That envolves something deeper, then. Please add this to the Wishlist section of the forum here: 

https://forum.dcs.world/forum/207-dcs-core-wish-list/

Maybe we can pick up this suggestion for a future feature. 

[RPY Variable]

8 hours ago, Lord Vader said:

Hello all

After we reviewed the tracks and observed the conditions, we believe we have found the culprit for your reports.

It's actually a feature in DCS, regarding GPS quality.

In your track @RPY Variable your F-16C is set to the Red Coalition. As such, the GPS quality is by default much lower than the Blue Coalition. In order to mitigate this, you can select "unrestricted sat nav" option in the Mission Editor or just select a Blue coalition side. 

I tested this myself with the DCS: F-16C Viper and with the DCS: A-10C II Warthog and you can observe the difference. 

Without proper or poor GPS guidance, the GBU-38 can have a CEP at about 30m or even more. So this is actually well modelled.

Thank you for your patience and, yes, this was a tricky one. 

Thanks for taking the time.

I understand the argument, I don't say I agree (don't think anyone cares), 30 meters of precision seems a lot to me no matter how bad the GPS is. Even more so with such unverifiable aspects as GPS guided accuracy of eastern world countries. Maybe if BLUE is 5m, then make RED it 10m or 12m, I don't know, but 30m, 40m even 50m seems like much. It is worse than dumb bomb level flight release from 20.000ft.

Be sure to stick this report on the refrigerator door because it will surely be a constant complaint XD. Thanks again for the time.

[Zholik]

On 2/6/2024 at 4:05 AM, skywalker22 said:

Exactly, forgot to say that. But note, Laser is only good to use in clean weather.

clouds dont affect sensors in dcs, you can use laser just fine

[okopanja]

On 2/7/2024 at 4:24 PM, Lord Vader said:

It's actually a feature in DCS, regarding GPS quality.

In your track @RPY Variable your F-16C is set to the Red Coalition. As such, the GPS quality is by default much lower than the Blue Coalition. In order to mitigate this, you can select "unrestricted sat nav" option in the Mission Editor or just select a Blue coalition side. 

Is it possible to provide some more technical explanation for this feature. E.g. the only thing I could correlate to was the Selective Availability which was in effect until May 2000.

[okopanja]

@Lord Vadercan we have more in-depth reasoning for the difference between blue/red? E.g. which signals are actually simulated in DCS?

 

[BIGNEWY]

Hi, 

GPS is a bluefor asset, it is that simple. Thus weapons using GPS on redfor will be less accurate. 

 

[okopanja]

27 minutes ago, BIGNEWY said:

Hi, 

GPS is a bluefor asset, it is that simple. Thus weapons using GPS on redfor will be less accurate. 

 

First thanks for answering,

My point here is the following:

- GPS can be affected externally either by rightful owner of 3rd party, e.g if e.g. civilian signals get degraded (e.g. if we are talking about China produced glide bombs)

- Also some traditional military signals offer only protection against spoofing and ECM

- Only the latest M code offers the protection which prevents other side using high precision due to the encryption

I see no reason why the same physical hardware would not be capable to utilize same precision for both blue/red since unless you implemented weapons to utilized encrypted mode, which would make it available only to one side in the conflict.

Until now:

- no GPS jammers exist in DCS

- no GPS spoofers exist in DCS

-  no ability to enter the encryption codes

- It appears we have only the GPS in game (not sure about Glonass, BeiDou, Galileo, perhaps others).

IMHO: the mission editor option to disable this is a good idea as long as your simulation in this respect is incomplete (I was hoping you would confirm to which extend you simulate and where actually mimicking starts).

Last but not least a comment on general situation on with so called game-changing decisions:

Finding out about this through at least 2 bug reports (where even 3rd party vendors are not aware of the changed rules) is far from ideal. Instead it would have been much better of ED stated this game rule explicitly. IMHO: there should be part of DCS Encyclopedia where each of such critical decisions/rules is properly documented e.g.:

1. Radar range for hornet/viper
2. Ever more realistic FM model changes
3. Countless AIM-120C changes
4. AIM-54 drag impact
5. R-27 no relocking
6. R-77 RWR launch warning of the rail
7. ...

All such decisions should be documented and should reference the release/beta version where it got introduced, together with some sort of justification (I do not really expect you to provide 100% details, but bare minimum which is understood by common player would be OK).

[BIGNEWY]

8 minutes ago, okopanja said:

IMHO: the mission editor option to disable this is a good idea as long as your simulation in this respect is incomplete.

Using unrestricted satnav check box in the mission options will help. 

[Notso]

On 2/6/2024 at 12:56 AM, BIGNEWY said:

Please ensure you are using the laser to get the correct range for the target, this will ensure the CEP is much smaller. 

thank you 

I know you later found the culprit of this bug as being a Blue vs Red GPS quality issue.  But I just want to address the laser thing.  Firing the laser is NOT (or should not) be required if you are transferring accurate coordinates to the bomb from the NAV system.  Using the TGP at all is not required to deliver accurate JDAMs, as long as the coordinates and elevation in the bomb are accurate.

However, if you are targeting and transferring coordinates derived FROM the TGP - then YES you should fire the laser to have accurate slant range to correctly produce the coordinates.  I just didn't want people being confused into thinking they HAD to use the TGP with laser ranging for accurate JDAM delivery.