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Implications of Commercial 1m Res Satellite
One-eyed Orbital Snake writes "Interesting essay in the NYT magazine (free login, yadda yadda) on commercial 1m resolution satellite photos, with the Sept. 24 launch of Space Images' Ikonos. Not much new, but well written and all in one place. References Clarke's 2061, Brin's Transparent Society, and ties it all up with a heartwarming 1st Amendment ribbon. Definitely worth a read."
I smell marketing opportunities.. Kinda the same way that your local phone company has to be paid not to list your name in the phone book.. I'm sure someone will have the bright idea to offer people the ability to block the satellite from taking pictures of their homes for $30/sq ft or something. Perhaps law-enforcement agencies will be purchasing the right to view certain areas on a continual basis.. Hmm.
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This kind of thing isn't going to make me go out and install a giant mirror over my home pointing back up into orbit. The CIA (you know..the real one..not the one on TV) has had this sort of technology at its disposal for decades. However... It never ceases to amaze me how many people scream bloody murder about privacy. I wouldn't care if the police set up 10 satellites all looking down on my poor little apartment. I don't do anything illegal to begin with -- why the hell should I care?
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Bowie J. Poag
Bowie J. Poag
High resolution sensors such as Landsat TM (25m) and SPOT PAN (10m) have repeat rates of the order of 28 days, as will the new generation of 1m satellites. Actually SPOT has a tilting sensor which gives it a revisit facility as well as the option of producing stereo pairs. This is also a feauture of the new satellites.The repeat period (a month) means that you cannot use these satellites for the kind of surveillance that a lot of people worry about. Combine this with the fact that 80% of the Earth's surface is cloud-covered at any time and you'll see what I mean. These sensors have no thermal infrared capabilities at this resolution so you can't use them for spotting tanks or anything like that. You CAN use it to spot semi-permanent structures such as missile launchers and dug-in tanks - but you've been able to do this with SPOT for a long time.
Another note on resolution - there is a theoretical limit on spatial resolution, determined by atmospheric scattering. It's about 15cm. So a spy sattelite, on a perfectcly clear day, could, just about, be used to tell what kind of car you are driving - certainly not to read the number plate (which is kind of hard from a nadir view anyway). Forget geostationary satellites - they sit at an altitude of 35800km over the equator which means you get oblique views of most stuff, and lousy resolution (15km). They're great for synoptic weather (and telecomms obviously) but that's about it.
The people who should be worrying about the new high-res satellites are the air-survey crews. This could well put them out of a job for medium-scale photogrammetric surveying.
Nick Yes
I am a PhD student in remote sensing...
-- "It's a sad day for American capitalism when a man can't fly a midget on a kite over Central Park" - Jim Moran
It is nice to see an American newspaper showing such understanding of a very important issue. I really wish we would see this kind of mainstream publication around the crypto issue (which for now is a lot more important - and really shares a lot with this debate (the long term vs short term esp.))
I'm not sure the transparency is all good though. As long as we are not able to excersise individual freedom, but are forced by violence into the obedience of autocratic governments (regardless of whether they are controlled by a dictator, corrupt lobbyists, or >50% of the population) letting the very people that we allow to dictate our lives know all about is very dangerous. Society as it exists works because we can get away with breaking the rules (smoking up, speeding, whatever).
However, like online piracy, and like crytography, and like a million other technologies that conservatives have deemed dangerous, this is not a matter of choice. We are not in a position to choose whether we like this or not - having an opinion is futile. Transparency is the future, like it or not, for better or worse.
It is my belief that was has to go is our current regimes. It is they, not itself, that turns transparency into a nightmare. For the "global village" that the article discusses to be real (and we all no that in a real village things can get pretty harsh for the weak and deviant - it is all but a utopia), power, and freedom must be evenly distributed among us and we will have to learn to rule ourselfs. For better or worse.
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Oh and they can't see through clouds either... (active microwave can but that's a different matter)
Nick
-- "It's a sad day for American capitalism when a man can't fly a midget on a kite over Central Park" - Jim Moran
>There's a theoretical limit (determined by the scale length of atmospheric turbulence) of 15cm.
Nick, a few questions:
What wavelength corresponds to that limit?
What does a plot of theoretical limit vs wavelength look like over the range far IR to UV? (ie, big divot at OH absorption, I'd guess)
Aren't there techniques (laser "false star") used by ground-based telescopes to get around atmospheric distortion, and can't they be used to enhance satellite resolution?
- Raleigh scattering - molecular scattering from gaseous atmospheric species. Goes as one over lambda to the 4. This is the reason why 'blue' spectral bands are useless for actually looking at the surface - it's also why the sky is blue...
- Aerosol scattering - this is all those pesky dust particles, water droplets and ice particles. generally asymmetric. Can be modelled using Mie theory. Rainbows are an obvious side effect.
- Absorption - the obvious ones - H2O, CO2 some trace gases. All these species have different absorption spectra - H2O (vapour) has two massive absorption bands in the mid-IR. Aerosols also absorb. UV absorption is behind the O3 layer.
Another effect to take into account is that maximum radiance is at about 550 nm - you're severly limited past the NIR by the fact that there ain't that much energy coming back up at you - which hurts resolution. Much the same for thermal IR (80m resolution) and passive microwave (tens of km) where the amount of enery is miniscule.The false star technique relies on shining a laser upwards against an essentially black background. To do the same thing with a satellite you would have to fire the laser downwards - and make sure it lands on a surface with perfectly predictable spectral response. So short of lugging a massive square of BaSO4 around I don't see how this can be done. Also - the footprint of the laser would be a lot bigger than the resolution you are going for. And mounting a 1200W laser on a satellite could be kinda tricky...
Good questions though.
Nick
-- "It's a sad day for American capitalism when a man can't fly a midget on a kite over Central Park" - Jim Moran
Satellite picture of Microsoft was available by clicking on some of the "Other Dates" links to the side of your image.
I am a programmer for a photogrammetric company (aerial surveying). Most of my work involves developing applications to correct for lens fall-off, brightness gradient, and sun flares in scanned aerial photography. I've been doing this bit for almost six years now and have been hearing from day one how these new up-and-coming high resolution imaging satellites would make our aircraft obsolete. From everything I've seen, its mostly marketing hype. 1m resolution is just that, 1 pixel == 1m x 1m, there is not a lot you can see in something that coarse. Sure roads, buildings, and cars are visible, but that is about it.
i s/hyper/guide/napp
Have a look at some NAPP photography if you want to *see* something:
http://edc.usgs.gov/Webglis/glisbin/guide.pl/gl
NULL
For 4 years I've been working on Remote sensing. I feel that there's a missconception about satellite imagery. 1m resolution is not so "Hi Res" imagery. Same imagery has been around for years in form of aerial photography, let's say, for more than 40 years. Yes, the times have changed, now images are processed and used with computers, you have powerfull geographic information systems, etc...but privacy is still the same... There's no way that 1m resolution can be used to see french girls topless in ibiza, or if you are wearing red shirts or even if you read marx or bradbury... 1m resolution can show if you built a new room in your house, or if that nice swiming pool you built in your house is big or small. Just like walking and watching from the street... In military applications, every government of the planet knows the satellite orbits, and no one will test that "hot new tank" while the satellite is above them. Russians knew that US planes and satellites were taking images during the cold war, and funny things happened, but I can't remember a serious discovery in the intelligence field, when everybody knew what was going around. Maybe in the first years it was secret, but quickly it became obvious that imagery was just a control tool, nor a real secret eye in the space. This reminds me "The Simpsons" when the goverment guys say they don't know where monty burns hides the 1 billion dollars note, but sattelites show that is not in the roof...that's the real thing... Real privacy violations are coming, but not 1m resolution images...maybe electromagnetic scaning of monitors activity, or laser microphones targeted to our windows, but...jejeje...not ikonos from the space... just my 2 cents...