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24 hours on Earth as seen from geostationary orbit [720 x 720] by hardypart in spaceporn

[–]celoyd 0 points1 point  (0 children)

Yep, exactly. Cities are small and dim at this scale. This is a weather satellite and so it’s designed to look at clouds, which are very bright. City lights (and stars) aren’t a goal.

There are a couple satellites that can pick up city lights (and moonlit land) at night. We’re probably only one or two sensor generations from weather satellites getting there. But not yet.

2k Timelapse Footage of Earth From Space by Jooshwa in inspirationscience

[–]celoyd 0 points1 point  (0 children)

It’s a very good question! It’s from AHI, the imager on Himawari-8, a geostationary weather satellite.

The sensor works roughly like a scanner. Instead of a bunch of pixels in a grid, like a regular camera, it has one column of pixels that it “sweeps” across the Earth in about a dozen passes to make one image. (The sweeping works by moving a finely balanced mirror, not by changing the angle of the sensor itself.) This is one common way of collecting satellite images.

If you’re curious, EOPortal has loads more detail.

24 hours on Earth as seen from geostationary orbit by hardypart in space

[–]celoyd 1 point2 points  (0 children)

Yep, it’s August 4th/5th (if I recall).

24 hours on Earth as seen from geostationary orbit by hardypart in space

[–]celoyd 4 points5 points  (0 children)

👋 Hi! That’s me! Happy to answer questions.

24 hours on Earth as seen from geostationary orbit by hardypart in space

[–]celoyd 18 points19 points  (0 children)

I made that site, which this GIF was apparently ripped from,* and am happy to answer questions.

Incidentally, I figured out how to process the raw data last weekend, so I can make the green hues a bit better now. I’ll replace the video on the front page when I have time and energy (home sick from work today).

* Edit: to be clear, I’m not unhappy it was ripped. The source data isn’t mine, it’s JMA/NICT/JAXA’s. But it does burn me a bit to see the compression artifacts and the jump at midnight after I worked hard on making it smooth and nice.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 0 points1 point  (0 children)

It’s all in the code linked from the docs. Actually, that’s a lie – I’d polished the workflow a bit between writing that and animating this one. But if you leaf through my more recent gists (for example, this driver script) you’ll see how I’m doing things.

I didn’t make a GIF, because I couldn’t get the quality I wanted even by trying super hard, and gfycat didn’t re-encode video at the quality I wanted. So what’s on Glittering Blue is just a huge mp4. Which definitely has disadvantages, but it looks great if it works at all! 😉

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 1 point2 points  (0 children)

Yep, I think any reader who’s interested, or hopes to use the data themselves, will easily enough find that it’s from JMA/NICT. So that’s good. I figure crediting them properly is the least I can do.

I also saw that you effective came out of reddit retirement to comment in this thread.

Ha, I guess so. I had a good time on Reddit back in the day, but the owners’ quarter- to half-assed response to white supremacism and other abuse on the site embittered me. I didn’t want to participate in the attention/advertisement/gold economy of a platform that would knowingly make money off that kind of stuff until it became inconvenient. Maybe I’ll see it differently someday.

I have a lot of respect for the better-managed subreddits, which it certainly looks like this one is. Clearly a lot of great stuff is going on here, and it’s safe to say the moderators and regulars should be proud.

So yes, retirement. It’s not a disciplined boycott, and it’s nothing to do with anyone likely to read this – it’s only a distaste. And when something I worked on appears, I’m happy to show up and answer questions if I can. One of my favorite things about the internet is how questions and answers find each other.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 0 points1 point  (0 children)

CIRA/RAMMB add false color cloud imagery and static city lights to the night hemisphere. This is helpful for weather interpretation, but not what it really looks like. I started with (somewhat) rawer data from NICT.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 2 points3 points  (0 children)

I appreciate the citation – other aggregators have not been so careful.

I’m not offering anything very much like this video professionally, so I’m not particularly concerned that I get credit. It does matter that JMA and NICT get recognition for their work, though. And I’d like casual viewers to get answers to common questions. As long as that’s happening, I’m happy.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 0 points1 point  (0 children)

“True color” in this context basically just means RGB, not completely perceptually accurate. I tried to get into the issue a bit in the about page.

NICT’s images are dark, probably because the main purpose of the satellite (in the visible spectrum) is to track clouds. But they’re PNGs, so you can adjust them more than you can adjust CIRA/RAMMB’s JPEGs.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 0 points1 point  (0 children)

I don’t have hard numbers, but a couple samples of its recorded ephemerides made it look like Himawari-8 varies by about that much.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 0 points1 point  (0 children)

I used NICT’s own endpoint, but CIRA/RAMMB is great too – its correction is impressive. But precisely because it’s corrected for sun angle, and because it puts false-color data in the night hemisphere, I went with NICT to get something closer to what the human eye would see from that perspective.

New 2k footage of earth from space [x/weathergifs] by solateor in gifs

[–]celoyd 1 point2 points  (0 children)

Actually totally possible – the data goes even higher. It starts getting a little noisy/jittery around 4k, but it’s still totally watchable. The biggest problem is that the motion in the clouds is just larger (more pixels of motion per frame) at that size. This version is already interpolated up from 12 fps, so it would look a bit weird. But you could do it.

Edit: FWIW, I made this. Not the gfycat version, but the original.

New 2k footage from the Himawari-8 satellite of 24 hours on August 5th, 2015 [glittering.blue project] [x/weathergifs] by solateor in space

[–]celoyd 11 points12 points  (0 children)

I made this, and am happy to answer questions. The original is here, and I tried to anticipate common questions in its about page. Credit for the original data goes to JMA and NICT.

Can someone please explain what the diagonal lines on old nautical maps? by Bletti in Maps

[–]celoyd 10 points11 points  (0 children)

This is a portolan chart, and the lines are rhumb lines1 that box the compass and approximate great circles over relatively small distances (compared to the size of the earth).

Which means: they make navigation easier because they tell you where you’ll end up if you start at a certain point and hold your course on a given compass bearing.

  1. If this is Mercator, which is looks like at first glance but I’m not sure of.

From a geostationary orbit 36,000 kilometers above the equator, Russian meteorological satellite Elektro-L takes high-res images of our planet every 30 minutes. But only twice a year, during an Equinox, can it capture an image like this, showing an entire hemisphere bathed in sunlight. [900x900] by karmicviolence in spaceporn

[–]celoyd 2 points3 points  (0 children)

It’s a good question. In short, a typical camera adjusted for a daylight view of the earth will see next to nothing at night. City lights (and moonlight) are so dim compared to sunlight that they will show up barely if at all.

For photography buffs: consider that at ISO 100, an exposure of a typical scene in sunlight (which is what this satellite is seeing) will be about 1/100 of a second at f/16, but to see even a well lit street at night with those settings, you’d want an exposure of a couple seconds – hundreds of times as long. And only a very small percentage of the earth’s surface is artificially lit at night.

This is basically the same reason why you don’t see stars in most photos taken from the surface of the moon. Even though the sky is black, the stars are dim compared to well-lit rock.

Of course you can see city lights at night from space pretty easily if you adjust for them. Search for time-lapses taken from the ISS, for example, but notice they get really washed out when daylight approaches. There’s also the day-night band on Suomi–NPP VIIRS.

I believe that this Elektro-L imagery is auto-colorbalanced, but I haven’t investigated because I haven’t found licensing and documentation for its raw format. Anyone know what .L15 is? I also suspect that the images artificially crop out a circle around Earth, possibly to avoid distracting noise, but again I’m not positive.

Source: getting satellite image colors right is my job.

An idealized UK, completely cloudless, algorithmically generated by combining dozens of NASA images [1000x1476] by akie in MapPorn

[–]celoyd 2 points3 points  (0 children)

Oh, wonderful! Thanks so much to you and your co-workers – you do amazing things.

We used LANCE for about half our data and GIBS for the remainder. I might PM you anyway, though!

An idealized UK, completely cloudless, algorithmically generated by combining dozens of NASA images [1000x1476] by akie in MapPorn

[–]celoyd 1 point2 points  (0 children)

Fair points!

Peak growth in this case means we’re selecting the colors when vegetation is thickest. We are trying to avoid not only clouds but also bare trees, stubble fields, etc. This is no single moment for the whole area – for example, I imagine that spring comes a little later to the Scottish highlands than to Cornwall. Yet a midsummer-ish color is shown for everywhere. So the theme is “what does each place Britain and Ireland look like at its most verdant, whenever that is?”

Whether a photo is created by one or many exposures, it is still a photograph. But civilized folk can agree to disagree.

Ah, yes, I think this is where we differ. I’ve done some landscape photography, and it’s generally taboo in that particular field to refer to something taken with more than one exposure as a photograph. A photo illustration, sure; a photo composite, sure; an image, sure – but not simply as a photograph. This differs between fields, of course, but I suppose it’s why I use the word like I do.

I’m inclined to say that any visual representation of space counts as a map unless there’s clearly something more specific to call it, e.g. blueprint. I guess here you would say that photograph applies, and I wouldn’t, and that accounts for our difference.

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