Does the Viper INS drift?

[Lace]

If I leave the GPS switch off, or disable GPS through the MP, does anybody know if the INS drift and at what rate?  Is this currently simulated?

[Hobel]

It looks like.

 

So yes.

 

 

Edited November 23, 2022 by Hobel

[_SteelFalcon_]

it does drift, but dunno how much tbh

[Lace]

Great, thanks!

[amalahama]

Are all INS fix modes modeled already?

[Tholozor]

You can do OFLY, FCR, HUD, and TGP fixes.

[amalahama]

Oh I didn't know it was already implemented! Cool! How does JDAM behave under GPS denied (e.g. pre 90s missions) environments? Are they affected by the lack of available GPS too?

[Topo]

13 hours ago, Tholozor said:

You can do OFLY, FCR, HUD, and TGP fixes.

I probably misunderstood, but is the procedure described in the video needed to change the position of the waypoints or to improve the accuracy of the navigation system's position?

[QuiGon]

17 hours ago, amalahama said:

Are all INS fix modes modeled already?

Officially yes, but they are partially broken and thus don't work properly.
 

2 hours ago, amalahama said:

Oh I didn't know it was already implemented! Cool! How does JDAM behave under GPS denied (e.g. pre 90s missions) environments? Are they affected by the lack of available GPS too?

AFAIK the JDAMs are not directly affected by the lack of GPS in DCS. If your aircraft INS has drifted though, you might supply a wrong target position to your JDAMs causing them to miss, so make sure your INS is in good condition before dropping JDAMs.
 

38 minutes ago, Topo said:

I probably misunderstood, but is the procedure described in the video needed to change the position of the waypoints or to improve the accuracy of the navigation system's position?

Yes, it's described in the video.

Edited November 25, 2022 by QuiGon

[Topo]

12 minutes ago, QuiGon said:

Yes, it's described in the video.

Sorry, i try to formulate the question better (my bad, terrible english): the procedure corrects a single wrong waypoint, or corrects the navigation error of the entire navigation system (and therefore the position of all waypoints) starting from the comparison of the known coordinates of a single waypoint with those that derive from on-board systems?

[QuiGon]

2 minutes ago, Topo said:

Sorry, i try to formulate the question better (my bad, terrible english): the procedure corrects a single wrong waypoint, or corrects the navigation error of the entire navigation system (and therefore the position of all waypoints) starting from the comparison of the known coordinates of a single waypoint with those that derive from on-board systems?

The latter. It affects the entire nav system, not a single waypoint position, as it corrects the accumulated drift of your INS.

Edited November 25, 2022 by QuiGon

[Topo]

18 minutes ago, QuiGon said:

The latter. It affects the entire nav system, not a single waypoint position, as it corrects the accumulated drift of your INS.

Wonderful, thank you!

[SickSidewinder9]

What I don't understand is why the GPS doesn't seem automatically correct for any nav errors.

[Sarge55]

23 hours ago, SickSidewinder9 said:

What I don't understand is why the GPS doesn't seem automatically correct for any nav errors.

The GPS does correct for INS drift normally.

However, if you are flying a mission which is set at a time before GPS (pre 1990's) was available or if the GPS system is down you will need to do an INS fix occasionally.  There are some missions in DCS set before GPS and some that simulate the loss of GPS service.

[SickSidewinder9]

I think what I'm seeing are changes in the way steerpoints are presented.  ie The steerpoint for something at ground level will not appear at ground level until 5-ish NM, and may just seem off in the HMD/HUD until very near. No idea if that's a bug or correct, but it's odd when used to how it was.

[Sarge55]

Is the steerpoint elevation set for ground level?

[SickSidewinder9]

On 11/29/2022 at 6:30 PM, Sarge55 said:

Is the steerpoint elevation set for ground level?

Yes.  But the indicator stays floating above the actual steerpoint untill gear is down, it seems.

Would love to see someone from ED comment on it so we could know the precise parameters.  Definitely throws off approach angle when not in direct visual or if not super familiar with terrain.

Edited December 2, 2022 by SickSidewinder9

[LastRifleRound]

On 11/25/2022 at 3:33 AM, QuiGon said:

Officially yes, but they are partially broken and thus don't work properly.
 

AFAIK the JDAMs are not directly affected by the lack of GPS in DCS. If your aircraft INS has drifted though, you might supply a wrong target position to your JDAMs causing them to miss, so make sure your INS is in good condition before dropping JDAMs.
 

Yes, it's described in the video.

 

What is broken about the update feature?

[QuiGon]

18 hours ago, LastRifleRound said:

What is broken about the update feature?

Currently the HUD continues to show the SPI with drift, even after a nav update/fix, while the TGP and HSD show the correct updated positions. This means the HUD will guide you to the wrong drop point when doing CCRP after having performed a nav update/fix. That should be fixed with the next OB update though.

Edited December 11, 2022 by QuiGon