TPOD + Elevated Target Surface = ???

I'm not sure if this is actually a bug, but it certainly seems to be one.

1. The TPOD using CCD(TV) seems to have difficulty recognizing that it is looking at an elevated surface, such as a bridge. Even when looking at the road-surface along the length of the bridge, only a small margin of the width of the surface is recognized to be above the hight of the water below the bridge.

EG if you let the cross-hair settle on the water surface, you get H6 for Hight 6 feet displayed, along with Long. & Lat. When targeting the surface of the bridge you can see H6 jump to H109, but only on a small margin of the width of the bridge.

2. When the road-surface of a bridge is targeted, the TPOD seems to still actually be targeting the ground level below the bridge. This can easily be recognized by targeting the road-surface of the bridge while looking along its length, and them moving to an angle 90° from the length. In other words, looking at the bridge from the side.

Instead of the road-surface of the bridge still being targeted, while looking from the side, the surface of the water below the bridge is being targeted, which will lead to a bomb landing under the bridge when approaching from the side.

Maybe the bridge is "transparent" for the tpod...

I think that's a general DCS issue as terrain and objects work quite differently. You could say that as far as the terrain database, from which all Targeting Pods take coordinates, is concerned, the bridge doesn't have dimensions.

That is normal for DCS and I think realistic too. Same happens if you target a vehicle and don’t use the laser - the bombs would fall on the ground behind it, because TPOD uses map coordinates and doesn’t “know” given object is there. That is also the reason why it is best to sweeten the solution and place your crosshairs on the tracks / wheel level.

I don't know, but it seems lazy and illogical. Engineers know there are buildings out there and bridges, etc. The TPOD reads the actual height of the target point. It would be silly to then ignore it, because it's on top of a man-made structure.

Of course one could always resort to only using GBU's or LMAV's, but I don't find it a viable proposition to offer the military, when all one would have to do is maintain the actual target-point on top of the targeted structure.

The TPOD reads the actual height of the target point. It would be silly to then ignore it, because it's on top of a man-made structure.

The aircraft doesn't know it's own height precisely, so even if the targets was known, there'd still be error.

The real TGP, creates a 'track' file that stores triangulation data i.e. when flying tangentially to the target, and sweetens the estimated position as it gets closer to the target.

There was an analysis of the TGP's accuracy in 2005 which estimated an error margin of CEP ~200m @ 15 NM, reducing to CEP ~20m @ 4 NM.

Using the laser range finder *might* improve accuracy but that is not perfect either as the target may be dark and a foreground/background object highly reflective i.e. the river (water vapour also reduces the laser range).

AFAIK most of this isn't modelled in DCS which instead has it's own limitations, however IMHO the error seen in game is similar in magnitude to that seen IRL.

Of course one could always resort to only using GBU's or LMAV's, but I don't find it a viable proposition to offer the military, when all one would have to do is maintain the actual target-point on top of the targeted structure.

As you've noticed, it's not always possible in game (or real life) and a realistic reason to use expensive precision weapons or plan/expect to require additional ordnance/flights against a 'difficult' target i.e. 3-6 Mk83 or 3-8 Mk82 per pass (number depends on bridge length, spans, etc.)

The aircraft doesn't know it's own height precisely, so even if the targets was known, there'd still be error.

 

The real TGP, creates a 'track' file that stores triangulation data i.e. when flying tangentially to the target, and sweetens the estimated position as it gets closer to the target.

 

There was an analysis of the TGP's accuracy in 2005 which showed an error margin of CEP ~30m @ 15 NM, reducing to CEP ~10m @ 3 NM.

 

Using the laser range finder *might* improve accuracy but that is not perfect either as the target may be dark and a foreground/background object highly reflective i.e. the river (water vapour also reduces the laser range).

 

AFAIK most of this isn't modelled in DCS which instead has it's own limitations, however IMHO the error seen in game is similar in magnitude to that seen IRL.

 

 

 

As you've noticed, it's not always possible in game (or real life) and a realistic reason to use expensive precision weapons or plan/expect to require additional ordnance/flights against a 'difficult' target i.e. 3-6 Mk83 or 3-8 Mk82 per pass (number depends on bridge length, spans, etc.)

Depending which table from that paper you are talking about but it was more like 100m at 10nm from what I remember, at least for coordinate errors or for JDAM targeting which is what the paper was about.

At any rate, I think in general you are right in the sense the real planes with their contrast lock systems aren't really well modeled in DCS at all. From what I've read of the DMT use in the gulf war it was challenging to be able to lock certain types of targets. Frankly its probably easier in DCS overall.

Depending which table from that paper you are talking about but it was more like 100m at 10nm from what I remember, at least for coordinate errors or for JDAM targeting which is what the paper was about.

Yes, you are correct, it's more like CEP ~200m @ 15 NM, reducing to CEP ~20m @ 4 NM.

I'd checked the wrong table, theoretical error vs flight test data :doh:

Honestly those sorts of errors likely exist with every TPOD. Making certain online "tactics" rather specious.

I don't know what this mystery document is, but it sounds like it's pertaining to gyroscopic precision and not GPS.

I don't see how it pertains to the TPOD (or ARBS for that matter) actually managing a target-point on a man-made structure, higher than the surrounding ground level.

I don't know what this mystery document is, but it sounds like it's pertaining to gyroscopic precision and not GPS.

 

I don't see how it pertains to the TPOD (or ARBS for that matter) actually managing a target-point on a man-made structure, higher than the surrounding ground level.

No mystery, publicly available master thesis from university of Tennessee using publicly available data about the litening pod. And it is 100% about GPS "accuracy" or lack thereof, plus the inaccuracies that arise when aligning things like TPOD's, inaccuracies in aiming gyros and systems, and all the other inaccuracies that arise. If you have a science or engineering background the term is "error propagation".

Targeting stuff higher than ground level goes back to the age old problem of correctly getting target height above ground. The targeting pod will have what is called a spherical targeting error (SEP) because you don't a) know the actual altitude of the plane with 100% precision b) know the actual slant range to the target with 100% precision. So you have XYZ errors for plane position, XYZ errors for target position. Which is what makes targeting JDAM's with the TPOD in absolute mode quite problematic. But even with the ARBS its just locking onto a contrast, not a target, and measuring an angular rate to get an "ish" slant range. I'm not sure what the error on the ARBS is but I'm sure its range dependent, and on the order of maybe 10's of meters (slant range) when used in the real world at a few km range. LRF's aren't perfect either.

I don't see how it pertains to the TPOD (or ARBS for that matter) actually managing a target-point on a man-made structure, higher than the surrounding ground level.

It's a thesis ...

• "An Analysis of Target Location Error Generated by the Litening Pod as Integrated on the AV-8B Harrier II"

... with the object to ascertain/improve the accuracy of the AV-8B TGP for use with JDAM (GPS) munitions.

It analyses inherent errors in the AV-8B/TGP systems and compares them to test flight data, the conclusion was that it had sufficient accuracy within approx. 6 NM for JDAMs.

Of note is that test flight data was more accurate than the analysis predicted, perhaps due to error cancellation or the TGP performing better than specification.

You can't get more specific :lol: