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Finding the B-21's hangar location from the stars in its press image

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Re: Finding the B-21's hangar location from the stars in its press image

#131

Post by evilotto »

dylan604 wrote: post #113
mk_stjames wrote: post #24

I feel like the entire thread should have led off with "This is in fact a publicly known hangar in Palmdale and this was known as public information as soon as the unveiling event occurred, and thus this is just an exercise to show how locating the spot could have been possible from just this photo as a technical demonstration." Because I guarantee there are going to be a hundred clickbait articles by various 'news'…

People have been doing photo analysis for a long long time, and have gotten quite good at doing geolocation based on details in the background that the average viewer ignores. Spy agencies are especially good at it. There's many a spy movie that offers glimpses into this, but The Good Shepard comes to mind. Even as a joking kind of thing, the opposite has been done. There's a famous exchange between Neil DeGrasse Tys…

There was an xkcd comic set in the future with the exact date calculated from the stars. https://xkcd-time.fandom.com/wiki/Astronomy

Re: Finding the B-21's hangar location from the stars in its press image

#132

Post by cjensen »

rootusrootus wrote: post #12

With the casual change from "34-35 degrees" to "lets draw a line at 34 degrees" followed by the "and this is where the press release was" I got the vibe that this was parallel construction. Still some good sleuthing, don't get me wrong, but still.

You're right. Vandenberg, Kirtland, Canon, Altus, and Little Rock are all matches for the latitude and there is no text explaining them away. Even the "it must be California because Northrup" is both (a) debatable and (b) doesn't exclude Vandenberg.

Re: Finding the B-21's hangar location from the stars in its press image

#134

Post by sva_ »

pifm_guy wrote: post #50

It's worth noting that stars can be seen even in daylight with the right software. That's because, while no individual star is visible, the exact angles between all stars is fixed, so you can do a brute force search of all possible orientations of the sky to find a matching one. In a 6 megapixel image of half blue sky, you effectively get an oversampling ratio of 3 million:1, so even with very bright sunlight obscuri…

I've never considered that but it makes perfect sense. Might try to code something up given some freetime.

Re: Finding the B-21's hangar location from the stars in its press image

#135

Post by jbverschoor »

fourthark wrote: post #110
dsfyu404ed wrote: post #13

Earlier quoted context omitted.

Also goes to show you the danger of tunnel vision. If they flew one to some air base outside DC for the roll out the author would be shooting from the hip and who knows what facility he'd have zero'd in on. Sure it might have been the same one because "the same facility as the B2" is an easy just-so story but you don't really know with any certainty.

It doesn’t fly yet, so that narrows it down a bit.

Do they’re trying to scare Russian with an airplane that can only be taxied around?

I wonder if it’s made out of proper material and not just some clay concept

Re: Finding the B-21's hangar location from the stars in its press image

#136

Post by 4gotunameagain »

protastus wrote: post #125
4gotunameagain wrote: post #88

Earlier quoted context omitted.

What does an optimization algorithm have to do with a brute force search? Even if your image patch is small, without previous images to compare, you need to brute force the entire sky? And how can "fft trickery" reduce the attitude state to 1 unknown ? 1 unknown with what units ? Sorry but I suspect you are making all these up.

The claims from pifm_guy are reasonable. This is a scenario with extremely high coding gain[1]. The DC value of the sky can be removed by high pass filtering. Finding the rigid transform (rotation+translation) between two images captured by the same camera, assuming no distortion[2], assuming the image pair has substantial intersection, doesn't require calibration. Dropping the "same camera" and "substantial intersec…

If the "DC value of the sky" could be removed with a simple high pass filter, then there would be no need of doing anything else. The positions of the stars in the sky would be known, and techniques like the one in the article would apply.

I have been working fine so far in startrackers for spacecraft without your tutorial in signal processing, but thanks for the offer

Re: Finding the B-21's hangar location from the stars in its press image

#138

Post by burntwater »

Sporktacular wrote: post #126
stuff4ben wrote: post #80

Earlier quoted context omitted.

Even if he did do this for the clicks, so what?

So it's manipulative. Like a sensational headline that buries the mundanity at the end. Lead with "this is already publicly known" so people can make an informed choice about where to direct their attention.

If the point of the article/twitter thread was to reveal the location of the hanger, as if that was previously a secret, then yes perhaps the title is misleading.

But that's not the point of the article. The point of the article was to reveal the location of the hanger using the stars and other metadata, and to explain how that was done. The journey was the story, not the destination.

Re: Finding the B-21's hangar location from the stars in its press image

#139

Post by UncleEntity »

Merad wrote: post #111
supernova87a wrote: post #98

He seems to use the hour estimate of 1:30am being a time when very few satellites are likely overhead as a sort of confirming factor. (I guess because many satellites are sun-synchronous around noon, and the USAF would purposely time the photo to not expose the aircraft to observation). But is that a very strong confirming factor? Is it likely that NG / USAF would be actively avoiding the potential for satellite imag…

> Is it likely that NG / USAF would be actively avoiding the potential for satellite imagery? Does it mean all the time it was being built, they avoided having it outside during the daytime? During the Cold War black projects like the F-117 did exactly that. IIRC they weren't necessarily limited to being out side only at night, but they were very careful about satellite orbits to make sure the secret aircraft wouldn'…

Not just secret projects.

When I was in the 82nd Airborne we had days where we didn’t do any outside training because the Soviet spy satellites were overhead. Estimated troop strength, deployment schedules, blada, blada.

Kind of nice because they generally left us alone as long as we stayed out of sight.

Re: Finding the B-21's hangar location from the stars in its press image

#140

Post by gmiller123456 »

There's a few highly suspect details in the way the author got the 34-35 degree estimate. Maybe he was just really lucky and the errors cancelled out, but don't count on using his method to produce similar results.

Polaris is about .8 degrees away from the celestial North pole, so using it alone can give a reading off by .8 degrees, and the orientation in the photo is actually nearing the worst case.

The horizon doesn't appear in the photo. I have done celestial navigation strictly as a hobby for fun, and using a sextant without a visible horizon results in a few degrees of error at best. And that's with the benefit of the sensation of gravity helping you estimate. It is theoretically possible to estimate the horizon using the man made parallel horizontal lines in the image, but the author doesn't give any indication he did that.

Additionally, the author used the angle measurement tool in Stellarium to measure the distance to another ambiguous horizon. This is incredibly odd, as just clicking on Polaris in Stellarium will tell you its elevation. But even more odd, is he would have had to explicitly set his latitude in the app in order to get that screenshot.

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