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And the third microsat company with operations coming online soon is Planet Labs: http://www.planet-labs.com

Robinson Meyer at “The Atlantic” did a nice overview two months ago: http://www.theatlantic.com/technology/archive/2014/01/silico...

It’s an interesting time in remote sensing.


The video field of view is 1.1 by 2 km: http://skybox.com/uploads/10/08/imageryandvideospecsheet.pdf

Purely speculating, not going on anything they’ve said: theoretically when they have more satellites you might be able to patch together a larger area with simultaneous video from several birds. You’d have a slightly ugly angle difference at the seam, of course. There may be technical constraints here that I’m not thinking of, though.

In any case, at 1 m GSD and 30 fps, 1.1 by 2 km is 66 megapixels a second. Even efficiently compressed, that’s a lot of information already.


sixothree 44 days ago | link

It looks more like the fov is 0.1 by 2 km (in this particular video).


Exactly. This is why distant city lights often twinkle even more than stars do: there’s more atmosphere between you and them than between you and the stars.

Another effect here is that Skybox’s video uses the pan band, which includes infrared to 900 nm[0], and smog is usually pretty transparent in NIR, depending.

0. http://skybox.com/uploads/10/08/imageryandvideospecsheet.pdf

And a third important factor is that smog is very diffuse (by definition: otherwise you call it a smoke plume), so if you have the bit depth you can just increase contrast until you get a good image.

(I work at Mapbox on satellite imagery, but wasn’t involved with this particular blog post; what I’m saying here is stuff that people in remote sensing Just Know.)


I took a break from dealing with an in-band null problem in image data to check HN, and here’s this. Oof.

Don’t represent missing data with a value in the same domain as real data.

Maybe I’m just grumpy, but that seems like a clear, persuasive, and generally realistic goal. In cases where you’re constrained to break that rule, at least approximate it. For example, if you’re stuck using strictly floats for a percentage like this one – without recourse to an undefined/null/none type – you can still use -1.0 or Inf or NaN and not draw the lines.


wonderzombie 212 days ago | link

You're not just grumpy. I think this is a good practice in general. Or maybe it's just you and I; when someone does not do this, I go cross-eyed.

It does introduce the null reference problem, but that's what it's there for and if you're not going to invent a nil-object, let's not try to paper it over. IMHO it's better to make it explicit.

I think this graph is awesome, BTW; I just liked your comment. I sympathize with folks putting something together quickly, for fun, and of course we've all written bugs into our programs. I also enjoy discussing programming philosophy.


I’ve worked with NASA and USGS a fair deal both for fun and professionally, and this is typical.

They are extremely competent and sincerely want you to have good data. They are also hampered by the bureaucratic limits of any large organization. So it’s like working with a large, well-run business that’s hired a lot of the best people in its field and is working on good problems, yet is large enough that it can’t move to meet the exact needs of any one customer.

But on top of that there are political concerns. They have an institutional fear that a congressperson in a budget debate is going to stand up and say something like “And apparently we’re paying the Geological Survey $N million a year to run a web server for something called geotiffs that tell you how tall hills are!” That’s my impression from reading between the lines, anyway; no government employee I know has been indiscreet enough to deliberately hint at such a fear.

For example, the best interface to SRTM isn’t from the agencies that made it, it’s a single-page project from Derek Watkins at the NYT: http://dwtkns.com/srtm/

Working with NASA in particular feels like working with an industry leader that has a mysterious policy against advertising, or even going out of its way to help you find resources. (Individuals do, but not the organization, at least not anywhere near in proportion to the number and value of its resources.)

NOAA too: they have some amazing satellite imagery that’s public domain, but they simply do not have the budget to do anything but the most halfassed job of hosting, publicizing, and documenting it, because from a funding perspective that’s frivolous. They barely archive their images, because no one with budget control gets why a weather agency should save its input data. Look up “VIIRS granule” – that’s technically open data, but yikes.

The resources are there, and if you make the effort to figure it out, the people who manage them are pretty much all a delight to work with. But you have to deal with the damage created by a political culture that too often treats our civilian space and geospatial agencies as afterthoughts rather than as highly multiplied public goods.


skyebook 220 days ago | link

With regards to your political argument, its something I've often thought about because it can go either way. There's the loaded language approach as you mention, but there's also the possibility of the hypothetical member of the House or Senate saying "And apparently we’re paying the Geological Survey $N million a year to run a web server that no one is making use of and funding data that no one seems to care about."

This would be a hard argument to defend against as it directly hits the value derived from the service rather than the idea that the service itself exists. In either case, I couldn't agree with you more that the civilian agencies really get a raw deal (and I'm sure its only compounded by the mostly stagnant level of people graduating with STEM degrees[1])

[1] http://www.nsf.gov/statistics/digest12/stem.cfm#3


I’d be interested to know the ratio of the L0 data size to the L2/3/4 data[0] size – in other words, how many downlinked bits of sensor readout are processed per bit of useful science data? Of course that won’t be a hard number; I’m just curious to get a sense of the general scale on which the pipeline reduces pixels to physical parameters.

0. http://en.wikipedia.org/wiki/Remote_sensing#Data_processing_...


Yet until a credible leadership figure actually _offered_ unconditional surrender, it was going to be war as usual.

But it wasn’t. The A-bombs were quite unusual. They were extraordinary weapons, and would have required extraordinary justifications to use on the military, let alone on civilians.

(To the argument that it wasn’t possible to target the military apart from civilians: that’s exactly why nuclear weapons are so problematic.)

it deliberately ignores both the wide diversity of opinion which existed within Japanese leadership

An alternate interpretation is to not take it alone, and to see it as deliberately summarizing the wide diversity of opinion which was already going through the complex process that you rightly point out. News of Nagasaki’s destruction interrupted a meeting by the Japanese Supreme War Council, not so much about whether to surrender as about how. I don’t think it’s facile at all to call this, in context, “ready to surrender”.

The US did not know the details of the meeting, of course, but they chose to spend 70,000 human lives on an assumption with no particular justification, while under no special immediate military threat – at that point, Japan was relatively contained, and the fear was that if left alone it would reach out again in a matter of months or decades, not weeks. The threat was diplomatic: that Japan might surrender to the USSR. That seems worth presenting as something other than the rueful conduct of justified, proportional warfare as an absolute last resort.

As an American, sometimes I look at other countries that haven’t come to terms with major war crimes – the Armenian Genocide, for example, or indeed Imperial Japan’s crimes in China – and I shake my head.

Then I remember that the US has the A-bombs on our record, and we’ve made it almost 70 years now without admitting as a nation (meaning in standard textbooks, in mainstream entertainment, etc.) that these were, by any sensible definition, crimes against humanity of the highest gravity.

There’s this objection people sometimes raise: that it’s easy to say these things if you weren’t there, if you weren’t under the pressures of command, knowing your nation’s people were dying by the day. That’s true. I don’t know what that was like. It’s easy for me to moralize from a distance. But that argument isn’t actually justifying the act of the A-bombings, merely moderating judgment on the people who did it. Saying they didn’t really know what they were doing is very different from it was a good idea.


greedo 319 days ago | link

You have the privilege of tarring the commanders of US forces as war criminals "of the highest gravity" because of the sacrifices US soldiers, sailors, airmen and marines made during WW2.

If you haven't already, do some research on how the Japanese fought at Okinawa. At the defensive plans they had in place for defending the Home Islands. The toll of an invasion would have been horrendous for both sides. This is without dispute by serious historians.

Your idea that the Japanese were "relatively contained," implying that there was no need to do any further action is almost laughable as a military or political strategy.

When you go to war, you should go to war til the other side cries "Uncle."

Furthermore, the idea that war should be "proportional" is also a sophomoric argument without merit. War is hell for a reason. If someone engages you in war, you fight them to the death. You don't go back and forth in a tit for tat manner that negates all of your advantages and magnifies theirs.

And to lump the A bombs with what Japan did to China? Read up on the Rape of Nanking. Or find out how many Chinese civilians the Japanese Army killed on the mainland. Or how they treated POWs during the Bataan Death March.

War is hell.


levosmetalo 319 days ago | link

> Furthermore, the idea that war should be "proportional" is also a sophomoric argument without merit. War is hell for a reason. If someone engages you in war, you fight them to the death. You don't go back and forth in a tit for tat manner that negates all of your advantages and magnifies theirs.

Did you just agree that people, army and paramilitary forces of Afghanistan are right to go to total war "to death" with the USA, USA army and USA civilians. Because even one innocent dead man in Afghanistan can justify action of, for example, poisoning NYC water supplies?

Or this "unproporional" punishment of enemy is justified only if it's the USA that is doing it, not when it suffers it?


greedo 318 days ago | link

I think it's entirely justifiable for any afghani to be joining the Taliban and fighting to kick out a foreign invader from their soil. Everyone has a right to defend their country's sovereignty.

I personally wouldn't advocate targeting civilians; but if there was no alternative, and my culture, country and way of life was being destroyed, I could see a rational actor choosing to do so.

The US would have been far better served by simply conducting a punitive raid in AFG to knock over the original Taliban and let the assorted tribes learn not to stir the hornets nest. Instead we've decimated the country without creating any real change. And we've also grown accustomed to a sanitized style of warfare where drone operators in Creech, Nevada plink small targets without working up a sweat.

War should be hell, lest we grow to like it too much.


kalms 319 days ago | link

The United States dropped two very big bombs on cities. Cities, not military installations. That's very close to being a war criminal in my opinion, realities of war be damned.


> You have the privilege of tarring the commanders of US forces as war criminals "of the highest gravity" because of the sacrifices US soldiers, sailors, airmen and marines made during WW2.

In reality, we Europeans have the privilege because of United Kingdom, Soviet, United States, Canada, Finland, and countless volunteers and freedom fighters from the occupied areas. I appreciate the sacrifices, suffering and determination from a nation I so admire; in fact we celebrate it once a year, but please remember that United States were never alone in the fight.


greedo 318 days ago | link

I didn't mean to imply that the US was the sole combatant; I was responding to the parent who was an American.

War is still hell. The Romans razed Carthage, a war crime? The Germans in WW1 bombed London, war crime? The British torched Dresden, war crime? The Nazis bombed Rotterdam, war crime?

It's far too easy to conflate "war" with war crime. Some feel that the two are synonymous. I think each generation has a tendency to feel superior and more advanced than the previous generation; I think this is naive and ill informed. We're all savages of a sort.


kalms 317 days ago | link

"Now we are all sons of bitches." — Kenneth Bainbridge

Yes, yes, yes and yes.

I'm not even saying that I would act differently if I were a military commander. War is hell, granted. But that doesn't make it right, and we should be honest with ourselves. It's not right. Killing innocents is not okay; using civilians as leverage in an act of terror is never okay.

We should strive to be better than that.


greedo 317 days ago | link

Striving is fine, but as some sage once said, "your enemy always has a vote." We're limited in how we act by how our opponents behave. And despite what Fukuyama said, I think that we'll see more conflict in this century than anyone expects.


vidarh 318 days ago | link

Their actions can be necessary, and still war crimes and/or abhorrent. These are not mutually exclusive.

We can be grateful for the outcome and many sacrifices and still speculate about whether or not specific actions were necessary and justifiable.

And we can actually recognise the atrocities committed by the Japanese military and question actions by the allies at the same time.

It is understandable that a lot of decisions were taken that had horrible outcomes, and that many of them were taken in good faith and probably the only viable decisions despite how atrocious they might seem in retrospect. That does not mean we should just gloss over everything.


hga 319 days ago | link

"The A-bombs were quite unusual. They were extraordinary weapons, and would have required extraordinary justifications to use on the military, let alone on civilians."

Extraordinarily efficient, one plane, one bomb, one city, but we'd already methodically bombed pretty much every other city (along with Kyoto for political reasons, the A-bomb targets and their alternates were reserved), with e.g. the firebombing of Tokyo killing a conservative 100,000.


GauntletWizard 319 days ago | link

To view anyone in Japan, or more accurately, anyone in any of the great powers as a "civilian" during the wartime of WW2 - is pretty naive. All of Europe, Japan, and America were in a state of Total War - Every available resource was being put towards the production of munitions, every able-bodied man was being drafted, every spare cent was being spent on the war.


Scramblejams 319 days ago | link

Yes, I sometimes wonder what a veteran of the American Revolutionary War thought when he first saw the Gatling gun.

What would be unusual is if weapon technology _didn't_ increase exponentially in lethality over time.

Given enough time even Little Boy will, to future generations, look to be nearly as puny as a flintlock. Hope we don't do ourselves in.


Dylan16807 319 days ago | link

If you want to bomb a target smaller than a city then you have to design smaller bombs.

If you want to target cities then you keep making city-sized bombs.

If you want to target larger areas, you're probably going to be most efficient by targeting the cities in that area; go back to the previous step of city-sized bombs.

What's the incentive to increase lethality? If you make huge nukes or equivalently powerful weapons, they overkill your target and have negative side effects back on the homeland.


svachalek 319 days ago | link

Even sub-city-sized weapons like the ones dropped on Japan are too large to actually launch in the modern world; the political repercussions are much too great. The only use for a nuclear arsenal is to promise Mutually Assured Destruction, and it really doesn't take much for that.

The dangerous super-weapons of the future are small, simple ones that can kill just the right person, anywhere, anytime. That arms race is happening right now, and progress is rapid.


hga 318 days ago | link

"Yes, I sometimes wonder what a veteran of the American Revolutionary War thought when he first saw the Gatling gun."

Compared to e.g. canister shot from canons I don't think it would have awed them that much (http://en.wikipedia.org/wiki/Canister_shot).

Since at least the Napoleonic Wars, which followed shortly after our Revolutionary war, artillery has generally been the biggest killer on the battlefield.


vidarh 318 days ago | link

> But it wasn’t. The A-bombs were quite unusual. They were extraordinary weapons, and would have required extraordinary justifications to use on the military, let alone on civilians.

They were extraordinary weapons, but as the article points out: The bombing campaigns were not, other than in doing the damage with much fewer bombs. Japan had seen similar levels of destruction in dozens of cities that summer, and was running out of larger undamaged cities.

With that context, they should require extraordinary justification to use, but no more so than the previous months of firebombing, and the focusing on the use of a nuclear bomb vs. "just" the fire bombing is detracting from the issue of how much of that overall bombing should have been acceptable and how much of it was necessary or served much purpose.

I don't want to excuse the A-bombs, but the article does make a compelling argument that they were not qualitatively different in the suffering caused.


emmelaich 319 days ago | link

I stunned that you compare the atomic bombing with the Armenian genocide.

The atom bombs saved millions of Japanese lives because the alternative was a protracted brutal ordinary war.

Reminder: the firebombing that preceded the atomic bombs killed a lot more.


a clever, possibly elegant, algorithm

It’s just barely clever enough that no one thought of it before. It has to be really simple, because the innermost loop (estimating how cloudy a given pixel is) runs several trillion times.

using tools anyone could use (aside from a massive server farm)

EC2’s m2.4xlarge (> 64 gigs of memory, 8 decent cores) is going for $0.14/hour right now. You could run ten of those all day and spend less than on dinner at a restaurant with cloth napkins.


Heh, yes, we seriously considered the Honda Civic full of external drives option.[0]

Some of our images were from NASA’s hot new GIBS[1] service, which was extremely fast. However, it’d only backfilled about 2/5 of the data we needed, so for the rest of it we were using a legacy endpoint that was launched around 2004ish and has some, let’s say, idiosyncratic caching and throttling systems.

Instead of setting up a special channel, we talked to them and figured out how to shotgun the downloads in a way that wouldn’t kill their cache or require them to give us special treatment. We thought of this on a Friday and wanted to have it ready when we came in on Monday, and it worked. Thus the somewhat blunt methods.

0. For any young persons in the audience, the reference is to “Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.” from Tanenbaum’s “Computer Networks”.

1. https://earthdata.nasa.gov/about-eosdis/system-description/g...


Blue Marble was a big inspiration here, and we’ve had fun comparing notes with some of the people who made it. Blue Marble is, however, ten years old, and has a number of (justifiable) limitations. You can get a sense of these if you zoom in on its depictions of, say, the Niger Delta, or the northern tip of Greenland.



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