Air to Ground Ranging (AGR)

[imacken]

Ok, we’re not getting anywhere, probably because I’m not explaining very well. I can’t relate the 30 degree slant to your diagram in post #30 (I think).

[hein22]

Ok, we’re not getting anywhere, probably because I’m not explaining very well. I can’t relate the 30 degree slant to your diagram in post #30 (I think).

 

I can't either. IMHO I think that if that diagram was applicable to radar ranging method then it'd be useless.

 

On the other hand, I do not know exactly how narrow a mechanical radar is able to shoot a beam. But seeing the upper and bottom altitudes at 1BAR scan and 40nm range it would suggest very narrow.

[Fri13]

 

I can't either. IMHO I think that if that diagram was applicable to radar ranging method then it'd be useless.

 

On the other hand, I do not know exactly how narrow a mechanical radar is able to shoot a beam. But seeing the upper and bottom altitudes at 1BAR scan and 40nm range it would suggest very narrow.

 

You can apply it, as a second diagram, just ignore the aircraft angle as would be in level.

 

The radar beam is about 2-3° wide and tall, so it is not very narrow for long ranges.

[maxTRX]

 

You can apply it, as a second diagram, just ignore the aircraft angle as would be in level.

 

The radar beam is about 2-3° wide and tall, so it is not very narrow for long ranges.

 

Well, AGR works to around 10nm max?

[imacken]

 

You can apply it, as a second diagram, just ignore the aircraft angle as would be in level.

 

The radar beam is about 2-3° wide and tall, so it is not very narrow for long ranges.

 

The problem is that your diagram shows the centre of the beam to be level in level flight whereas we know it is actually at 30 degrees. I'm sure we're missing something, but on the face of it that doesn't stack up.

[Fri13]

 

The problem is that your diagram shows the centre of the beam to be level in level flight whereas we know it is actually at 30 degrees. I'm sure we're missing something, but on the face of it that doesn't stack up.

 

Ignore that, take the concept and adapt of second (middle).

the radar is not accurate. It is very wide beam at long range.

And flashlight effect grows smaller your radar angle is on the ground.

 

It doesn't matter is your radar 30 degree or 45 degree or 15 degree, it is always far less accurate than if it would be 90 degree.

 

You are now stuck to 30 degree in level flight, as I have explained you want to range the ground where you either see through HUD, you have a some kind benefit to start to see where you are targeting etc.

 

Your radar is always inaccurate if you don't increase angle of it enough and get it ranging flat terrain so it has easy time to estimate what you want to range, but it is better than just measuring altitude from below aircraft and assuming aircraft and target altitudes are same.

 

The AGR is there just to get the target altitude relation to aircraft so proper impact point can be calculated. But radar is not like a optical targeting with laser ranging (as well inaccurate at long ranges and shallow angles etc).

 

And if you fly at 15 000 ft and you get 30 000 ft slant range, your radar angle is 60°, not 30°.

Meaning radar is pointing at maximum deflection downward (+/-60° scan range).

​​​​

 

At 30 000 ft slant range, and 2.5° beam width you are scanning 1308 ft (0.215 nmi) range on flat ground. From it, what is your target position as what is taken as center of ranging is questionable for that solution at that range. Closer you get, more accurate you become.

Ie. At 8000 ft you are already 348 ft area. Enough for bomb dropping? You can't have a great accuracy than by luck, but you are getting bomb explode in good area of effect for target.

 

Compare that to ARBS system that can calculate slant range with sub-CEP values, so bomb own flight dynamics is the limiting factor for accuracy, meaning you can't get more accurate than that not even with laser guided bomb unit.

 

The AGR is just a one mean there to assist in uncertain situations, not to be the solution for accurate engagements.

​​​​​​ Why targeting pods are so important.

[imacken]

I’ll absorb that later, but I was referring to the angle from level flight path, i.e. 30 degrees.

[Fri13]

I’ll absorb that later, but I was referring to the angle from level flight path, i.e. 30 degrees.

 

Yes, sorry thought it wrong. You are correct about 30 000 ft for 30 degrees from aircraft point of view. I made mistake at the 30 degree from vertical and not from 90 degree, that results to 60 degree from vertical.

 

But it still doesn't matter do you fly straight or do you dive, the radar is inaccurate with it couple degree wide beam and inaccuracy gets bigger further you point it at lower angles and more uneven or cluttered terrain there is to measure range.

​​​

​​​​​The compromise is acceptable for error in ranging accuracy if you need to get bomb with area of effect in hundreds of feets, but for gun it becomes less useful for longer ranges and you need to get closer.closer.

 

But shallower attack you do, less accurate you are as radar beam scans larger surface area.

so what you want is to be able tell and switch the targeting modes that are more proper for your weapon realise. So you can switch to example radar altitude trigonometry calculation as it can be a lot more accurate if you can expect your aircraft position on terrain and target altitude to be very close to each others. You wouldn't like to use radar for that.

 

As well in many missions you must go silently, as even normal tanks can have a RWR that can pinpoint source direction in ten degree accuracy. So if you turn your radar On to do ranging, they get warning and they can spoof you or even turn air defense at you to expected direction and altitude.

 

And at low altitude you likely are approaching behind the terrain cover so your radar ranging is not fast enough to give you calculation on moment you drop behind the cover and only fly over the target area after release.