Laser ranging from a distance to another

[Akenar-99]

Hello,

 

I observed something strange regarding how the system records the range detected by the laser.

When you lase, the range is stored and showed even if you stop lasing, changing if your helicopter moves. So far everything is normal.

The problem starts when you lase another object at another distance. It gives you the correct range but if your pulse is to short, when you stop lasing, it returns back to a value between the former range and the new one.

 

Example :

We are stationnary (to make it easy).

We lase an object at 8000m for a few seconds. When the laser is off, the TADS and the TSD kekp showing 8000.

Then, we lase an object at 3000m for a few seconds. The TADS and the TSD show the new value, but when we stop lasing, it returns back to a value between the old one (8000) and the new one (3000).

The longer we lase, the closer to the new one it is. Lase 0.5 seconds, it dispays 7000. Lase 1.5 seconds, it shows 4000 (roughly).

 

Which means that if you want to make a new ranging and storing, you have to lase for a few seconds.

Is it normal ?

If yes, why does it work like this (technically)?

 

Thank you !

PS : I also observed that if lasing at more than 10km, you see 9999, which is normal. If you store a point at more than 10km, the storing will be accepted by the system but will store a point at exactly 10km in the middle of nowhere. I don't know if it is normal.

Laser test.trk

Edited November 16, 2023 by Akenar-99

[TheGhostOfDefi]

I hate to say it but could you provide a short track file in that you show us exactly what you described.

[admiki]

2 hours ago, Akenar-99 said:

PS : I also observed that if lasing at more than 10km, you see 9999, which is normal. If you store a point at more than 10km, the storing will be accepted by the system but will store a point at exactly 10km in the middle of nowhere. I don't know if it is normal.

System knows where you are and in which direction you are looking. It can go in that direction for 9999m, so that's where it stores the point.

And like the @TheGhostOfDefi said, track would be helpful.

[Akenar-99]

My bad !

It is done on my initial message.

I can see that if you don't lase long enough to have a stabilized range (5 seconds), the value changes continiously.

It may explain why the points I store use to drift.

Edited November 16, 2023 by Akenar-99

[FalcoGer]

I suspect it has to do with the target state estimator (TSE).

When using the TADS, the aircraft uses a combination of the laser range rate of change and the TADS rate of rotation to track moving targets. So when you put in a new range with the laser, the TSE assumes that the target is moving because of the rate of change for the range is suddenly not 0. I'm not sure how long into the past the system looks. Though if that were the case, I would expect the range to be running away into the direction of change once you stop lasing after too short of a time, which is what I have observed before. I don't recall there being a situation where it tries to average the range over 5 seconds for me.

It might also be a bug.

Or I could be completely wrong. Who knows.

Edited December 27, 2023 by FalcoGer