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CCIP pipper fluctuation


St4RgAz3R

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The ccip pipper seems to fluctuate very oddly when transitioning from ground to a runway. For example when you re doing a run with ccip to some targets on the runway as soon as the ccip pipper transitions from ground to the tarmac of the runway it fluctuates up and down making aiming with it very difficult which shouldn't be the case as the ground and runway are on the same elevation. It seems to do it only with the tarmac of the runway like it confuses it as if you re passing by some ground with big terain elevation  , when passing by hills, trees, buildings etc it has some slight fluctuation which is expected but works fine. I've included a track , don't know if it's a bug or not but worth taking a look at it

m2000 ccip piper.trk

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Yes, this is actually a feature

Runways have a very low reflectivity compared to normal terrain (look at SAR image, runways are mostly black) and combined with the fairly large radar beam (about 3° -3dB, and 6° lobe zero) even pointing on the runway, it gets more return from the surrounding grass. 

This causes the ranging processing to lock on the grass and since this is off axis it deduces a wrong elevation.

I have no proof it does the same IRL, but it plausibly does. It certainly does it with water/land boundaries, such as rivers.

You can disable TAS on the PCA, it will use the radio altimeter to compute the CCIP, and since terrain is generally well flat it will be accurate.

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17 hours ago, Kercheiz said:

Yes, this is actually a feature

Runways have a very low reflectivity compared to normal terrain (look at SAR image, runways are mostly black) and combined with the fairly large radar beam (about 3° -3dB, and 6° lobe zero) even pointing on the runway, it gets more return from the surrounding grass. 

This causes the ranging processing to lock on the grass and since this is off axis it deduces a wrong elevation.

I have no proof it does the same IRL, but it plausibly does. It certainly does it with water/land boundaries, such as rivers.

You can disable TAS on the PCA, it will use the radio altimeter to compute the CCIP, and since terrain is generally well flat it will be accurate.

Oh wow! Didn't know the radar simulation would be in such depths. But it makes sense as you put it. This module surpises me more and more each time i learn new things about it. Good job from the developers. And as you suggested disabling TAS helps keep the pipper steady even when transitioning from ground to the runway so in that kind of scenario it is better off. Thanks for your help @Kercheiz

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