INS pre 1984 mission INS drift

[RogueRunner]

Did a mission last night with friends and the INS drift seemed excessive. Is that correct?

 

Can someone please explain the in flight INS update procedure to me?

[Svend_Dellepude]

You can use tacan update if you have a tacan station stored in the HSI/TACAN page. But it doesn't always work as intended and you might have to do it a couple of times before it works. But it wont ever be spot on as when you took off.

You should also be able to cancel the last update, but that option is missing atm.

I think It's pretty much still wip.

 

There is a lengthy thread in here about how drift affects your bombing solution and basically makes using dumb impossible after 15 mins of flight.

 

 

Edited August 29, 2021 by Svend_Dellepude

[Swift.]

I haven't been able to find a good way of measuring drift in DCS because waypoints don't move even after two hours of circling with no GPS.

 

If you've got a good repeatable method Is be interested in seeing it as I'm sure there is a bug that can be reported here. Real like ASN-139 drift rates are negligible at best, I've see test results of 0.0 NM/Hr drift

[Svend_Dellepude]

45 minutes ago, Swiftwin9s said:

I haven't been able to find a good way of measuring drift in DCS because waypoints don't move even after two hours of circling with no GPS.

 

If you've got a good repeatable method Is be interested in seeing it as I'm sure there is a bug that can be reported here. Real like ASN-139 drift rates are negligible at best, I've see test results of 0.0 NM/Hr drift

 

Just browse through the tread above your post, all tracks shows INS drift.

Could be interesting if the tracks worked differently on your system though.

[Swift.]

Just now, Svend_Dellepude said:

 

Just browse through the tread above your post, all tracks shows INS drift.

Could be interesting if the tracks worked differently on your system though.

What I did was create a waypoint and slave the pod to it to check the location, then undesignate the WP and circle for hours, then upon redesignating, you'd expect the pod to point at a drift location. However the pod and the diamond in the HUD pointed at the original location

[Svend_Dellepude]

Looking through the thread there where actually no tracks, just screenshots.

 

The TPOD is not affected, neither is the radar if you track something. Then you will get the correct coordinates every time. The HUD and helmet IIRC are affected.

 

With precise coordinates enabled on the HSI page you will see drift on the ground while parked. Just speed up time and you will notice.

 

 

Edited August 29, 2021 by Svend_Dellepude

[Svend_Dellepude]

Try for instance to place a steerpoint on a ground unit and then fly around for half an hour.

Bring some mavericks and then designate that steerpoint. The maverick triangle will point at the ground unit, but the target diamond will be offset.

[Swift.]

1 hour ago, Svend_Dellepude said:

Try for instance to place a steerpoint on a ground unit and then fly around for half an hour.

Bring some mavericks and then designate that steerpoint. The maverick triangle will point at the ground unit, but the target diamond will be offset.

Thats effectively what I did, but the Target Diamond was bang on. I suppose its possible that having the pod onboard meant nothing drifted at all, but still....

[Svend_Dellepude]

4 hours ago, Swiftwin9s said:

I suppose its possible that having the pod onboard meant nothing drifted at all, but still....

 

Nah. From the tests i did, INS drifted no matter what i was carrying. Don't know why you didn't see any drift. For that you would need to make a track.

[IvanK]

On 8/29/2021 at 7:06 PM, Svend_Dellepude said:

You can use tacan update if you have a tacan station stored in the HSI/TACAN page. But it doesn't always work as intended and you might have to do it a couple of times before it works. But it wont ever be spot on as when you took off.

You should also be able to cancel the last update, but that option is missing atm.

I think It's pretty much still wip.

 

There is a lengthy thread in here about how drift affects your bombing solution and basically makes using dumb impossible after 15 mins of flight.

 

 

 

The Update routines are not yet implemented as far as I can make out. FWIW A Tacan update is about the lowest order update there is/was. The single best update possible is/was the Overfly update.

 

Perhaps they think everyone will be flying with POS/AINS so no real need for the update routines ??

Edited August 30, 2021 by IvanK

[Harker]

1 hour ago, IvanK said:

Perhaps they think everyone will be flying with POS/AINS so no real need for the update routines ??

 

True, navigating and attacking ground targets effectively without GPS is not really possible, considering the rate and weird implementation of drift and the inability to use some update options. I did find that DSG worked though.

However, the INS/GPS simulation is still marked WIP in the Roadmap, so they'll likely flesh out the system more.

[Tholozor]

5 hours ago, IvanK said:

The Update routines are not yet implemented as far as I can make out. FWIW A Tacan update is about the lowest order update there is/was. The single best update possible is/was the Overfly update.

 

Perhaps they think everyone will be flying with POS/AINS so no real need for the update routines ??

 

The UPDT function on the HSI works. You can perform a DSG update off a TGT point, or TCN update as long as the TACAN station is programmed into the MC.

[IvanK]

The UPDT option on the HSI brings up the ACPT REJ options but alas does not do anything. What should happen when performing an update is the calculated error should be displayed in the centre upper portion of the HSI. The pilot then evaluates the error and decides to apply the update by pressing ACPT or reject the update by pressing REJ. See graphic below. Without any displayed error you are achieving nothing. So at the moment it is not implemented. Same occurs with the various DSG options.

 

Graphic below in POS/INS Attempted TCN update on Batumi 16X which is in the TACAN data base.

 

[Tholozor]

It may not show the computed difference (which I agree should be present as-per the NATOPS), but it does update when accepted.

Edited August 31, 2021 by Tholozor

[Svend_Dellepude]

 

3 hours ago, Tholozor said:

You can perform a DSG update off a TGT point

How do you do that?

When I try the dsg option it updates to my current A/C position and not the position where my sensor(s) are looking

[Tholozor]

6 minutes ago, Svend_Dellepude said:

 

How do you do that?

When I try the dsg option it updates to my current A/C position and not the position where my sensor(s) are looking

Most commonly I use WPDSG off a waypoint to make the TGT point I update from, usually as a post-flight update, but sometimes as a fence point overfly update if I think I need it.

Edited August 31, 2021 by Tholozor

[Svend_Dellepude]

That's what I do too, or maybe I misunderstand.

What I do is: 

I have a steerpoint where I know the location, Select it as my target ( i made a mission with a bunker at the steerpoint and nothing else for miles), Lock it up with the radar or TPOD, and use the update/DSG/ACPT on the HSI.

That just moves that steerpoint to my current location and messes drift up even more.

If i do an overfly and use DSG update when over the location it works, which it shouldn't.

 

[Tholozor]

Currently the DSG update will update your aircraft's position to the position of the designation (basically seems like it's only working as an overfly fix). It probably isn't taking sensor data into account.

Edited August 31, 2021 by Tholozor

[Svend_Dellepude]

Yeah! 

I thought you had it working as it was supposed to.

[IvanK]

I got the TCN update to work ... minus the error display.

Though in the process discovered another bug. If trying to enter Lat Long in the TACAN data table it will only accept a Lat or Long whichever is the first entered, but the other coordinate is not accepted.

 

Tholozor using WPTDSG doesnt seem a logical thing to me. WPTDSG is going to form the TGT on the position that will be subject to system drift, so updating on that is updating on "itself" so to speak is it not ?

 

What is the purpose of a post flight Ovfly update in the Sim ? I understand the reasoning and purpose IRL but don't see the value in the sim.

 

Do in OVFLY updates (Both manual and Auto) work in the Sim . I have tried and dont really see working .... off to test some more

[Tholozor]

50 minutes ago, IvanK said:

Tholozor using WPTDSG doesnt seem a logical thing to me. WPTDSG is going to form the TGT on the position that will be subject to system drift, so updating on that is updating on "itself" so to speak is it not ?

 

What is the purpose of a post flight Ovfly update in the Sim ? I understand the reasoning and purpose IRL but don't see the value in the sim

If I return from a sortie with a drifted INS, I can make a waypoint on my exact position via F10 after parking, WPDSG, and perform a DSG update to correct my aircraft's position to those exact coordinates without having to shut down and realign with an updated Waypoint 0.

 

I always perform a post-flight update if I plan to rearm and refuel for another sortie.

 

If I need to perform an update mid-flight and TACAN is not available or I want a more accurate update, I can program a waypoint I intend to fly over (maybe a bridge or something), WPDSG, and DSG update as I fly over it and correct my position. It doesn't matter that the INS is drifted, because the coordinates of the waypoint are absolute inside the computer.

 

Does it follow the correct procedure for DSG outlined in the NATOPS? No, definitely not; as you pointed out the error correction is missing from the display and it's ignoring the use of sensors for updating the position of the designation. It's working backwards in a sense: rather than updating the aircraft's position based on a pilot-induced correction of the observed difference, it's just making the designated point the aircraft's new position (basically a visual nav fix like in the Tomcat or Viggen).

[IvanK]

Ok Re arm refuel and post flight update makes sense.

 

Just been out trying various update modes. Started POS INS with Drift established by sitting on the ground for 1 Hr before take off to be 217/0.5nm. WYPT the intersection of the rwys at POTI. Airborne both HUD Designated diamond and EXP 2 Stabilsed cue show drift in relation to rwy intersection as expected. Attempted RDR designation, refined the designation to the runway intersection attempted DSG update .... no error just pressed ACPT .... no change error still present. Next attempted DSG UPDT using the HUD to refine the designation to the Rwy intersection same deal no change.

 

So then attempted both Manual and AUTO Overfly update with TDC assigned to the HI then activated TDC as I overflew the runway intersection, neither worked.

I presume in your method of Overfly update you press  DSG as you fly over the WYPT  then ACPT ?

 

Then performed TCN update and pressed ACPT ... it worked.

 

So to me, the only UPDT that works using correct procedure (minus error display) is the TCN update. HUD,RDR and Overfly dont.

Edited August 31, 2021 by IvanK

[Tholozor]

I press ACPT as I fly over the intended overfly point, not the presented designation point.

 

Currently the DSG update method only works as a visual fix. All the processes described in the NATOPS regarding using the HUD, radar, and other sensors for the DSG update are non-functional.

Edited August 31, 2021 by Tholozor

[IvanK]

Another point. UPDT option should it be displayed/available if in POS/AINS ?

Edited September 1, 2021 by IvanK

[Steinsch]

I have not found any recent information about working INS update methods. Does anyone know if all navigation fix functions have been implemented to be used in pre GPS scenarios?