jarlrmai
Senior Member.
Source: https://www.youtube.com/watch?v=YYLKK6ZlCHc
This guy is apparently a pilot/wso and is claiming Go Fast range display is not accurateExternal Quote:
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F-16 Pilot Chris Lehto's Interpretation of the GoFast footage [Focus, Parallax, Inaccurate Range]
- Thread starter jarlrmai
- Start date
Source: https://www.youtube.com/watch?v=YYLKK6ZlCHc
DavidB66
Senior Member.
The guy may be an excellent flyer, but he doesn't seem to understand parallax or camera focus. His argument near the beginning seems to assume that parallax effects would make distant objects appear to move faster than close ones, which is the reverse of the case, but it's difficult to be sure because he doesn't really state his conclusion. His demonstration towards the end of the video is misconceived because the objects on his floor are relatively close to the camera, where the choice of focal length really does make a difference. Beyond a relatively short distance (100 meters? 1 km?) the rays of light reaching the camera from an object are effectively parallel.
He may be right about the range display, but I don't think he explains how come the screen is showing a definite range [RNG} as soon as the target is 'acquired'. If the range indicator is inaccurate that is pretty important.
jarlrmai
Senior Member.
Yes he is unaware of hyperfocal distance. He also uses the V/C measure to make a point about how the speed of the object, but surely that figure is based on the rate of change of the RNG data he claims is wrong...
I have being trying a lot recently to work out where that RNG figure comes from as far as I can tell it can only come from the RADAR, the laser for ranging works for direct line to the ground up to 18 nautical miles, it is not intended to range A/A targets. If the laser were turned on in A/A mode it would give likely range to the ground providing the ocean would reflect the laser correctly as there's no way it can range the target as it's far to small. If the range were to the ocean I think that would be ~7.1 nautical miles not ~3-4 we see
In A/G mode the LTD/R flashes if the laser is ranging, in Go Fast the ATFLIR is in A/A mode from what I can tell but LTD/R is not flashing anyway whatever that means if anything in A/A mode.
So his claim is kind of like what I've been wondering, if there is a track providing range (the theory being a weather balloon with a RADAR reflector) then why no other radar data displayed on the FLIR MFD?
It could be they only have range for some reason or they are only asking for range to be displayed on the MFD for the ATFLIR, I'm trying to find non L+S slaved ATLFIR footage with ranges displayed to see if I can see anything similar, but most ATFLIR videos are L+S because if you have a RADAR track why would you not slave 1st if you really wanted to see it without trying to manually slew and capture?
In Go Fast if they have a track and that is providing the range and they are not messing around with auto track like has been suggested, why not SLAVE 1st to get your auto track?
It could be the nature of what is shown in Go Fast, they have a track, but they are messing around trying to manually grab the auto track. Which is an unusual situation because generally if you had a track and you really wanted to put the ATFLIR on it you'd L+S slave 1st then autotrack on that and L+S would be boxed, unless you L+S acquired it, then autotracked, then turned L+S off maybe.
He also goes on about how Mick needs to speak to a pilot, well you know Mick has tried to talk to them right? Maybe you could be that pilot he speaks to..
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DebunkMee
New Member
If the pilots are not getting any radar returns from the object, is there a way for the plane's systems to deduce the distance to the object based on the IR video data alone? It would have to make an assumption about the true size of the object first (which is probably going to be fighter plane-size) and then based on that assumption calculate how far away it is based on how small it is in the video. But if the object were to be 2 times smaller or larger, then the estimated distance is also off by x2.
jarlrmai
Senior Member.
Not that are documented in the sim docs we are working from, the laser ranger is only used for ranging the ground in A/G mode.
jarlrmai
Senior Member.
@Mick West perhaps you can get an interview with this guy?
Yeah, I suggested that on his YouTube page.
I'm going to have to at least make a short rebuttal video explaining depth of field and hyperfocal distance, but it would be good to get clarification from him as to exactly what his argument is. It seems pretty clear in the video, but it's such a fundamental misunderstanding, so I'd like to talk to him about it.
#ufotwitter is gleefully sharing his video this morning.
jarlrmai
Senior Member.
Yeah I figured it would get traction, because of the source.
For Go Fast his main "real" claim is the the range is wrong for some reason.
AmberRobot
Senior Member.
I stopped at the point when he said you can't focus on two things at five miles and at ten miles Simultaneously. Maybe I'll continue watching more at some point but this is laughably false. He seems to think a camera focus on only one distance and everything else should be out of focus. If he replaces "miles" with "inches" that may be true, but for him to preface his argument by saying he's going to use physics and geometry he's off to an extremely rocky start.
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jarlrmai
Senior Member.
Yeah his main real new "claim" that needs looking at is that the RNG figure in Go Fast is wrong. No-one with a big profile as a Navy source (Fravor/Graves/Underwood/Dietrich) has ever claimed this as far as I know. it's simplest attack on the debunk essentially claim a key figure is wrong. The problem is that the footage would probably look different if they were tracking a target at 7NM (ground level at the FLIR angle) that was moving fast I would imagine the object speed to create a track that looks like the parallax effect would be extreme, as in during the ground track phase it would be almost impossible to manually catch it.
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DavidB66
Senior Member.
I don't see any comment from you under the video in question. Is it somewhere else, or is he maybe blocking you? It would be prize hypocrisy if he complains that you don't talk to pilots and then blocks you!
Scrolling through the comments on YT, I did notice that Lehto had responded to a question about the range (RNG) data, as follows:
jarlrmai
Senior Member.
I don't think in A/A mode there is any other system that can provide a range other than the RADAR. He acknowledges the LTD/R doesn't fire.
Link 16 seems to be the shared track network, ie a track from another RADAR (ship/plane etc) being broadcast to the jet.
The range must come from somewhere and that somewhere can only be RADAR, remember the RADAR is on 1 MFD and the ATLFIR is on the other, perhaps there are modes/setups/configs where you choose what data from the RADAR is overlaid on the ATLFIR MFD and you can choose only range and V/C etc etc.
The pilot just flies forward with a slight bank.
It's unclear what he means by "I initially tried graphing the engagement using the ranges on the screen and it doesn't work.", graphing it based on the numbers is what we did here years ago and it makes perfect sense for a slow moving object at 13,000 feet and a few degrees to the left of the jet.
AmberRobot
Senior Member.
I watched a little more and he even demonstrates the focus issue by moving his hands back and forth within inches of a camera, implying this would scale to miles. He doesn't mention that depth of field isn't just about focal length it is also about aperture size and focal ratio. If he stopped his camera way down he could show even at inches he could get multiple things in focus simultaneously.
Imagine how bad landscape photography would look if what he is saying were true.
He doesn't mention the focal lengths, the aperture sizes, the focal ratios or the exposure times of the camera being used in those videos so it isn't as simple as just thinking about geometry and a single focal length.
Imagine how bad landscape photography would look if what he is saying were true.
He doesn't mention the focal lengths, the aperture sizes, the focal ratios or the exposure times of the camera being used in those videos so it isn't as simple as just thinking about geometry and a single focal length.
jarlrmai
Senior Member.
The main issue for his theory is https://en.wikipedia.org/wiki/Hyperfocal_distance
In optics and photography, hyperfocal distance is a distance beyond which all objects can be brought into an "acceptable" focus. As the hyperfocal distance is the focus distance giving the maximum depth of field, it is the most desirable distance to set the focus of a fixed-focus camera.[1] The hyperfocal distance is entirely dependent upon what level of sharpness is considered to be acceptable.
AmberRobot
Senior Member.
Yes, and this is fairly rudimentary knowledge for people used to working with optics and photography. If he gave some details of the camera used we could work out the hyperfocal distance and put the argument to bed.
The focus issue really just needs some good examples of something with approximately a 1° FOV looking at two things, one being less than miles away, and the other being at least twice as far away. See what the focus difference is.
I think I'll go for a bike ride with my IR P900 (1° FOV at 2000mm) see if I can get something specific.
I think I'll go for a bike ride with my IR P900 (1° FOV at 2000mm) see if I can get something specific.
mikenos
New Member
Chris does make a mess of his explanation of focus but he is correct that the sharpness of the ocean reduces once the ATFLIR locks onto the object. Which would suggest that the ATFLIR is not at maximum focal length for the duration of the video as some are suggesting.
Would be interested to see this addressed in your rebuttal @Mick West.
DebunkMee
New Member
Even if there was no video compression the shutter speed of the camera will still create motion blur for moving objects.
DavidB66
Senior Member.
Another point that occurs to me on reading Lehto's comments at #11 again is that he clearly doesn't know how the RNG data on the display is derived, or where it comes from. Neither do I, but then I don't go round boasting about being a Top Gun pilot, and dismissing other people's views based on my mastery of the inside of a cockpit. More seriously, if he doesn't know the source of the data, how can he just brush it aside as unreliable? Simply from viewing the video, it is evident that the RNG data appears on screen as soon as the system 'acquires' the target, and then varies slightly up or down, in a way that suggests continuous real time monitoring of the range. What is Lehto's explanation for this? Does he think that the system enters in, and then modifies. completely arbitrary figures?
Agent K
Senior Member
Passive ranging is possible, generally based on assumptions about the target's speed, not size, in which case a "go fast" assumption is more likely than a "go slow" assumption. But if the pod is in ground track mode, then it should just estimate the range to the ground, yet it estimates half that range. I'm not convinced that it couldn't get a range estimate from the radar or laser rangefinder.
Agent K
Senior Member
I don't buy the focus argument. Here's an F-16 tracked by a Sniper pod, and the ground beneath it.
Motion blur is usually the bigger problem.
Source: https://youtu.be/Yi9d8bstWsE?t=76
Motion blur is usually the bigger problem.
Source: https://youtu.be/Yi9d8bstWsE?t=76
Agent K
Senior Member
He mistakenly thought the 'L' in the FLIR1 video stood for "Laser", then correctly said that it stands for "Left" in the Gimbal video, but then called it "Laser" again in the Go Fast video.
He says he was an F-16 pilot, which suggests that he may be unfamiliar with the ATFLIR pod, which is mounted on the F-18.
Source: https://youtu.be/qXWG1Trw88E?t=431
He says he was an F-16 pilot, which suggests that he may be unfamiliar with the ATFLIR pod, which is mounted on the F-18.
Source: https://youtu.be/qXWG1Trw88E?t=431
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Here I show the far shore (>4 Miles) and some trees on a central spit of land (2 miles) and on the near shore (about 0.5 miles) all in focus at 2000mm (1° FOV)
Here I focus first on the near shore (0.5 miles) and then pan over to the far shore (>3.5 miles), which is slightly out of focus. I then focus on the far shore and pan back to the near shore, which is still in focus.
I took a bunch of other videos and photos. Some of this is rendered a bit less compelling due to heat haze, but it demonstrates the principle.
jarlrmai
Senior Member.
Yeah it's getting a bit silly now I assume there will be no response to Mick's request to chat, despite having called him out for not speaking to a fighter pilot.
So far all this guy has managed to do is make fighter pilots seen like they are bad at interpreting footage from fighter jets.
He is in Portugal, so may will check his YouTube comments in the morning. I also pinged him on Twitter.
On point: the footage of a Jet with the ground behind it "out of focus" is from here
Source: https://youtu.be/wCA5xmYeQC8?t=93
That's not out of focus, it's some kind of video echo. Seems like persistence between frames. Nothing like that is seeing in the ATFLIR footage.
Agent K
Senior Member
He misinterpreted the "glowing aura" in the Gimbal video. Maybe he's not used to seeing that much image sharpening, even though pilots asked for it.
Agent K
Senior Member
Looks like bad deinterlacing.
I thought that at first, but there seem to be more that two frames in some parts of the image. Maybe a combination.
The ATFLIR videos seem to be interlaced.
Agent K
Senior Member
jarlrmai
Senior Member.
There's an interesting section in the Star SAFIRE manual that seems to relate to image processing done for white/black hot modes, in the examples given the objects have corresponding inverted halos, however it's unclear if this is related to the processing or not.
Edge sharpening as an option is also mentioned in the manual.
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jimmyslippin
Active Member
So the relevant parts of the video are 7:13, 13:36 and 17:46.
Being charitable, I think he may be suggesting that the L/R indicator would flash if the laser was firing, not necessarily that the L means laser.
Of course that could be easily cleared up by someone familiar with the ATFLIR display, though the chances of getting someone to actually talk about it seem to be pretty slim.
Daniel F
Member
He also points at the small 'o' next to R which denotes degrees of right. He seems to mistake this o and says its the situational awareness dot ( that white dot that drifts around the edge of screen in other videos ) and because of its position centre above means that we are looking straight ahead.
But , to be fair, in beginning he does explain that the symbology on these atflirs is different because of branding; and that the systems are basically the same except for the symbols- so I can personally put this down to initial unfamiliarity with some of the symbols.
jarlrmai
Senior Member.
This is the LTD/R indicator (LASER TARGET DESIGNATOR / RANGER) on the ATLFIR
Laser Status Indication - The laser status display provides 6 labels as follows:
The manual also says LTD/R then switches to LTD only in the display statuses, this could be a typo in the manual, or some version difference between the sim and the real ATLFIR. Or it could mean that the display shows it as there in A/A mode but there is no option to use it in A/A mode.
Laser Status Indication - The laser status display provides 6 labels as follows:
- LTD/R (flashing) - Laser is firing with ranging available.
- LTD (flashing) - Laser is firing with no ranging available.
- LTD (steady) - Laser is in standby.
The manual also says LTD/R then switches to LTD only in the display statuses, this could be a typo in the manual, or some version difference between the sim and the real ATLFIR. Or it could mean that the display shows it as there in A/A mode but there is no option to use it in A/A mode.
FatPhil
Senior Member.
Like interlacing, it's the combination of multiple fields into one frame. However, it's lacking the "interlacing" part of interlacing - a reduced spacial resolution being restored by alternating between the multiple fields. It looks more like motion compensation. Several fields over time (seems to be more than 2) are being combined such that the object of interest can be displayed with less noise. Alas this smears the information elsewhere in the frame. To be sure, I'd like to see how it handles trickier cases, such as the target banking.
Daniel F
Member
He says ' I think we are in ground mode '
That he thinks they picked it up visually and that they were probably sent there by another radar.
When he says ground mode I'm presuming that is the A/G you are referring to ?
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