Mark Point Inaccuracy

[Avio]

I created a mark point for a target, came in using CCRP high drag bombs, only to find the mark point to be a little off from the actual target. This happened at Sinai map.

Anyone else noticed this before? Is it a map coordinate issue, or the F16 mark point issue?

 

[RogueSpecterGaming]

1 hour ago, Avio said:

I created a mark point for a target, came in using CCRP high drag bombs, only to find the mark point to be a little off from the actual target. This happened at Sinai map.

Anyone else noticed this before? Is it a map coordinate issue, or the F16 mark point issue?

 

Can you post a short track of what you are talking about? 

Depending on the direction you came in from when you placed the markpoint initially it will appear slightly off if you come in from another direction. 

 

[LorenLuke]

1 hour ago, Avio said:

I created a mark point for a target, came in using CCRP high drag bombs, only to find the mark point to be a little off from the actual target. This happened at Sinai map.

Anyone else noticed this before? Is it a map coordinate issue, or the F16 mark point issue?

 

F-16 only has a GPS-corrected INS, not a full Enhanced GPS-INS (EGI) navigation system. So when you make a mark point, it's an offset based on the INS present position. As you turn, especially for sharp maneuvers, the INS will drift, and with it, your markpoints (and really every waypoint, coordinate, and such in the jet) will drift as well, moving them off-target.

[Avio]

Thanks much folks. I was under impression the GPS/INS in F16 is similar to the EGI in the F15E, which gives exact location plotting.

That being the case, does it mean for JDAMs they would all hit a little off from targets too? Or they should be spot-on since they are guided via satellite GPS?

 

[Dača]

2 hours ago, LorenLuke said:

F-16 only has a GPS-corrected INS, not a full Enhanced GPS-INS (EGI) navigation system. So when you make a mark point, it's an offset based on the INS present position. As you turn, especially for sharp maneuvers, the INS will drift, and with it, your markpoints (and really every waypoint, coordinate, and such in the jet) will drift as well, moving them off-target.

Can we do anything in flight to combat this drift? I know of FIX and A-CAL options on ICP. Should we re-align INS in Air mode ? Or are there some other solutions ?

25 minutes ago, Avio said:

Thanks much folks. I was under impression the GPS/INS in F16 is similar to the EGI in the F15E, which gives exact location plotting.

That being the case, does it mean for JDAMs they would all hit a little off from targets too? Or they should be spot-on since they are guided via satellite GPS?

 

JDAM will already hit slightly off from target, even if mark point is precisely sitting on a ground vehicle. I tested this. In real life, JDAM has 5 meters radius where it will hit. After all it targets INS coordinate and coordinate is not point, but area. So do not engage tanks and maybe heavy armored vehicles with JDAM. For pin point accuracy use laser guided bombs and mavericks.

[Gilligan]

6 hours ago, Dača said:

Can we do anything in flight to combat this drift? I know of FIX and A-CAL options on ICP. Should we re-align INS in Air mode ? Or are there some other solutions ?

 

No.

7 hours ago, Avio said:

Thanks much folks. I was under impression the GPS/INS in F16 is similar to the EGI in the F15E, which gives exact location plotting.

That being the case, does it mean for JDAMs they would all hit a little off from targets too? Or they should be spot-on since they are guided via satellite GPS?

 

Pre-planned CCRP strikes are not possible in the F16C in DCS. You must correct steerpoint/markpoint drift with the TGP or HUD for accurate CCRP drops. 

Edited August 27 by Gilligan

[BIGNEWY]

GPS-Era / STRD HDG Alignment

First, let’s start with the most common form of alignment in DCS, GPS-era using a STRD HDG alignment. This is the simplest, fastest, and most common for single- and multi-player. With power to the avionics systems, set the INS switch to STRD HDG and then set the GPS switch to ON. It’s important that the MIDS switch remains in the OFF position.

After about 12 seconds, you’ll see an ALIGN indication on the HUD.

You’ll then verify the STRD HDG alignment by going to the DED INS page and check the latitude, longitude, and altitude against your location on the F10 map view.

After about 60 seconds, you should be aligned and confirm this by the ADI flags being retracted; HSI showing correct magnetic heading, DME, bearing pointer and CDI deflection; roll and pitch correct on the HUD; and RDY should be flashing on the INS alignment DED page after less than 2 minutes.

We can now switch the INS switch from STRD HDG to NAV. On the DED INS alignment page, confirm that GPS TIME is displayed one minute after the GPS switch is set to ON. Note that this may take longer if the aircraft is under cover like a hardened aircraft bunker. As such, it is best to align out of cover.

With good GPS TIME, set the MIDS switch from OFF to ON.

After alignment with GPS correction, you can expect no more than 40 meters of INS drift. Further, if you zeroize the GPS or are flying a REDFOR Viper, you can expect an INS drift of 100 meters or more.

 

GPS-Era / Normal Alignment

A normal alignment is much like the STRD HDG Alignment, but we’ll need to manually enter the aircraft starting location because we’re not using a known, STRD HDG location.

To start though, we’ll in the INS switch to NORM and not STRD HDG this time. Then set GPS to ON, verify MIDS to OFF, and wait for ALIGN on the HUD after about 12 seconds.

The big difference is now going to the DED INS alignment page and entering the aircraft’s latitude, longitude, and altitude as shown on the F10 map.

Once done, we’ll verify ADI, HSI, and HUD as before and wait for the flashing RDY indication on the DED INS alignment page after about 8 minutes. Once flashing, set the INS switch from NORM to NAV and verify GPS TIME indication. With that, set the MIDS switch from OFF to ON.

 

These will be the most common alignment scenarios when performing a cold start. However, you may come across a mission or campaign with a date prior to the GPS era. In that case, we’ll only align based on INS with no GPS correction.

 

Non-GPS Era / STRD HDG Alignment

Like the GPS-era, set the INS switch from OFF to STRD HDG and wait for the ALIGN indication on the HUD. Then, verify the DED INS alignment page latitude, longitude, and altitude to the F10 map data and verify ADI, HSI HUD, and wait for the flashing RDY indication.

We can now move the INS switch to NAV.

Once airborne, you’ll then want to conduct alignment FIX procedures using Overfly, targeting pod, HUD, or FCR to remove accumulated INS drift. Please see the earlier videos on fix taking.

 

Non-GPS Era / Normal HDG Alignment

The last weight-on-wheels we’ll look at is doing a normal alignment at a mission date prior to GPS.

Set the INS switch from OFF to NORM and wait for the ALIGN indication on the HUD.

From the DED INS alignment page, enter the aircraft’s latitude, longitude, and elevation using the F-10 map.

Next, verify the DED INS alignment page latitude, longitude, and altitude to the F10 map data and verify ADI, HSI HUD, and wait for the flashing RDY indication after about eight minutes.

We can now set the INS switch to NAV.

Once airborne, you’ll then want to conduct alignment FIX procedures using Overfly, targeting pod, HUD, or FCR to remove accumulated INS drift. Please see the earlier videos on fix taking.

 

So far, we’ve only been talking about weight-on-wheels alignment procedures. We’ll now shift gears and discuss in-flight alignment. We’ll start with the more common GPS-era procedure.

 

GPS-Era / In-Flight Alignment

First, set the INS switch to FLT ALIGN and flight straight and level until the ADI flag is retracted. You’ll see INS FLT ALIGN on the DED and STBY on the HUD.

Maintain straight and level flight and enter your compass magnetic heading within 20 seconds on the DED and verify that the pitch ladder is displayed on the HUD.

Continue to fly straight and level until the ALIGN is replaced with the maximum G value on the HUD and then return the INS switch to the NAV position.

 

Non-GPS-Era / In-Flight Alignment

Last, for an in-flight alignment with no GPS, set the INS switch to FLT ALIGN and fly straight and level until the ADI OFF flag is removed. INS FLT ALIGN should appear on the DED and STBY on the HUD.

Fly straight and level and enter your magnetic heading on the DED within 20 seconds while ALIGN appears on the HUD, replacing the maximum G indication.

We’ll now perform an OFLY FIX within the next 30 seconds. It is required we perform a second OFLY FIX within two minutes to correctly perform velocity calculations.

Keep flying straight and level, and once the maximum G field replaces the ALIGN indication, you are done.

For best INS alignment, you may wish to perform an OFLY, HUD, FCR, or TGP alignment every 15 minutes for best possible navigation and acceptable weapon accuracy.

 

Manual Alignment as Backup

The manual alignment is a backup alignment designed to provide get-home capability only.

[Dača]

2 hours ago, BIGNEWY said:

GPS-Era / STRD HDG Alignment

First, let’s start with the most common form of alignment in DCS, GPS-era using a STRD HDG alignment. This is the simplest, fastest, and most common for single- and multi-player. With power to the avionics systems, set the INS switch to STRD HDG and then set the GPS switch to ON. It’s important that the MIDS switch remains in the OFF position.

After about 12 seconds, you’ll see an ALIGN indication on the HUD.

You’ll then verify the STRD HDG alignment by going to the DED INS page and check the latitude, longitude, and altitude against your location on the F10 map view.

After about 60 seconds, you should be aligned and confirm this by the ADI flags being retracted; HSI showing correct magnetic heading, DME, bearing pointer and CDI deflection; roll and pitch correct on the HUD; and RDY should be flashing on the INS alignment DED page after less than 2 minutes.

We can now switch the INS switch from STRD HDG to NAV. On the DED INS alignment page, confirm that GPS TIME is displayed one minute after the GPS switch is set to ON. Note that this may take longer if the aircraft is under cover like a hardened aircraft bunker. As such, it is best to align out of cover.

With good GPS TIME, set the MIDS switch from OFF to ON.

After alignment with GPS correction, you can expect no more than 40 meters of INS drift. Further, if you zeroize the GPS or are flying a REDFOR Viper, you can expect an INS drift of 100 meters or more.

 

GPS-Era / Normal Alignment

A normal alignment is much like the STRD HDG Alignment, but we’ll need to manually enter the aircraft starting location because we’re not using a known, STRD HDG location.

To start though, we’ll in the INS switch to NORM and not STRD HDG this time. Then set GPS to ON, verify MIDS to OFF, and wait for ALIGN on the HUD after about 12 seconds.

The big difference is now going to the DED INS alignment page and entering the aircraft’s latitude, longitude, and altitude as shown on the F10 map.

Once done, we’ll verify ADI, HSI, and HUD as before and wait for the flashing RDY indication on the DED INS alignment page after about 8 minutes. Once flashing, set the INS switch from NORM to NAV and verify GPS TIME indication. With that, set the MIDS switch from OFF to ON.

 

These will be the most common alignment scenarios when performing a cold start. However, you may come across a mission or campaign with a date prior to the GPS era. In that case, we’ll only align based on INS with no GPS correction.

 

Non-GPS Era / STRD HDG Alignment

Like the GPS-era, set the INS switch from OFF to STRD HDG and wait for the ALIGN indication on the HUD. Then, verify the DED INS alignment page latitude, longitude, and altitude to the F10 map data and verify ADI, HSI HUD, and wait for the flashing RDY indication.

We can now move the INS switch to NAV.

Once airborne, you’ll then want to conduct alignment FIX procedures using Overfly, targeting pod, HUD, or FCR to remove accumulated INS drift. Please see the earlier videos on fix taking.

 

Non-GPS Era / Normal HDG Alignment

The last weight-on-wheels we’ll look at is doing a normal alignment at a mission date prior to GPS.

Set the INS switch from OFF to NORM and wait for the ALIGN indication on the HUD.

From the DED INS alignment page, enter the aircraft’s latitude, longitude, and elevation using the F-10 map.

Next, verify the DED INS alignment page latitude, longitude, and altitude to the F10 map data and verify ADI, HSI HUD, and wait for the flashing RDY indication after about eight minutes.

We can now set the INS switch to NAV.

Once airborne, you’ll then want to conduct alignment FIX procedures using Overfly, targeting pod, HUD, or FCR to remove accumulated INS drift. Please see the earlier videos on fix taking.

 

So far, we’ve only been talking about weight-on-wheels alignment procedures. We’ll now shift gears and discuss in-flight alignment. We’ll start with the more common GPS-era procedure.

 

GPS-Era / In-Flight Alignment

First, set the INS switch to FLT ALIGN and flight straight and level until the ADI flag is retracted. You’ll see INS FLT ALIGN on the DED and STBY on the HUD.

Maintain straight and level flight and enter your compass magnetic heading within 20 seconds on the DED and verify that the pitch ladder is displayed on the HUD.

Continue to fly straight and level until the ALIGN is replaced with the maximum G value on the HUD and then return the INS switch to the NAV position.

 

Non-GPS-Era / In-Flight Alignment

Last, for an in-flight alignment with no GPS, set the INS switch to FLT ALIGN and fly straight and level until the ADI OFF flag is removed. INS FLT ALIGN should appear on the DED and STBY on the HUD.

Fly straight and level and enter your magnetic heading on the DED within 20 seconds while ALIGN appears on the HUD, replacing the maximum G indication.

We’ll now perform an OFLY FIX within the next 30 seconds. It is required we perform a second OFLY FIX within two minutes to correctly perform velocity calculations.

Keep flying straight and level, and once the maximum G field replaces the ALIGN indication, you are done.

For best INS alignment, you may wish to perform an OFLY, HUD, FCR, or TGP alignment every 15 minutes for best possible navigation and acceptable weapon accuracy.

 

Manual Alignment as Backup

The manual alignment is a backup alignment designed to provide get-home capability only.

Thanks !

[falconzx]

At the current state of the module, what we observed is not an inaccuracy related to the INS+GPS. Taking care of the standard procedures, that @BIGNEWY kindly reminded us, the drift is within the expected amounts, expecially when observing it through a Targeting pod in INS tracking mode. What we continue to find very odd is the constant misalignment of the SPI/Steerpoint symbology on the HUD, (given that what a TGP is showing in INR is the current INS solution for that coordinates+elevation). That Square, or diamond, is never aligned to the same point where TGP is pointing, there is always a difference and in some missions i've flown that discrepancy became very big (more than 200ft). I don't know how to reproduce the steps to make that misalign bigger, but it's never correct, even when just took off with a hot started jet.
Seems there is always an elevation error, because the symbology seems to drift over/under the ground so it moves changing the view perspective. But, for example the calculated SPI for CCRP is never the HUD symbol (just try a good drop to see it), but the actual INS postion shown by a Targeting pod in INR, so it's the HUD to be inaccurate.

This is the issue i think it's making the DTOS mode quite useless with GP ballistic bombs, if you don't have a TGP all the designations made by the HUD are wrong.

Aswell, expecially in the pre-GPS-era operations, without a TGP even the INS fixes made by HUD are inaccurate.
 

Edited 2 hours ago by falconzx