India Launches World's First Stereo Imaging Satellite 339
sgups writes "India will tomorrow inaugurate a new launch pad at its Satish Dhawan space port near Chennai, on the south-east coast, by putting the world's first stereographic mapping satellite into orbit.
The most innovative feature of the 1.6-tonne Cartosat-1 is its pair of cameras, which will give stereo images of the earth's surface that can distinguish features down to 2.5 metres across. They will directly generate three-dimensional maps that have until now been achievable only indirectly, by combining data from a large number of satellite passes over the same place.
"Such a stereographic imaging system does not exist in the civil sector anywhere else," says Mr Nair, chairman of the Bangalore-based Indian Space Research Organisation (Isro). "It will give information about heights that will be very useful in applications such as planning power lines."
Cartosat-1 will join what is already the world's largest cluster of non-military remote sensing satellites. Six Indian spacecraft are already observing the earth with a wide range of instruments."
Imagine the Possibilities (Score:2, Interesting)
Six Indian spacecraft are already observing the earth with a wide range of instruments."
Though probably none are currently tracking CowboyNeal.
What? How far apart... (Score:3, Interesting)
Heights? (Score:3, Interesting)
I don't get (Score:4, Interesting)
Geologic Mapping (Score:2, Interesting)
Why two cameras needed? (Score:5, Interesting)
That said, given the resolution with which we know the position of a given satellite, and the low resolution of the source image in this case, what advantage does using two cameras give you, vs. taking one camera and snapping two pictures in quick succession?
Maybe they can't be snapped quickly enough? But then, you'd think the larger parallax would be helpful, not harmful.) I know consumer cameras have the basic tech now to take a snapshot of the CCD state and process it later, that tech ought to scale right with the CCD resolution, whatever it is.
Maybe this is so you can choose the parallax direction, instead of the orbit forcing your choice? Does the image processing need the parallax to show up in some particular direction relative to the light source to work?
Honest questions; knowledgeable answers appreciated. (As you can see, I can talk out of my ass too
Not the distance between the cameras (Score:5, Interesting)
This is just supposition, based on the fact that two cameras on a satellite would not be far enough apart to generate parallax.
Three Corner Sat (Score:4, Interesting)
http://threecornersat.jpl.nasa.gov/ [nasa.gov]
http://nasa.asu.edu/ [asu.edu]
https://spacegrant.colorado.edu/tiki-index.php?pa
Unfortunately, the two of our satellites that got launched were released at 50,000 km instead of 100,000 km so they burnt up before they could power up.
http://www.spacetoday.net/Summary/2737 [spacetoday.net]
Re:I don't get (Score:2, Interesting)
Re:Heights? (Score:3, Interesting)
Yes, but they're not passive. You either have to send an energy wave down or somebody holding a GPS unit. This satellite could get that data passively.
"How would a picture be more accurate?"
I didn't RTFA so I don't know the context of the word 'Accurate'. I can tell you, though, that I've seen stereoscopic images taken from airplanes travelling over
Also, concievably, they could take color images. There's no way you could get color data via the other methods you mentioned. If you're looking down over a city, for example, a stereo color image will tell you a LOT more than anything radar or GPS could do. In the sense that the data is more useful, yes, it's very accurate.
Somebody is conflating ... (Score:3, Interesting)
Re:Why two cameras needed? (Score:3, Interesting)
I didn't have anything to do with the design of this, but I have to assume that two cameras are necessary because you'd have to tilt the camera otherwise. Normally, a satcam is pointed straight down. If you get two images a few meters apart, you can't derive much z-axis data from them. With the cameras tilted so that they converge at the approximate height of the sat, you can derive z-axis information and work out the height of items on the ground.
Of course, you don't *need* two cameras. As I said, you could tilt the camera and take a snapshot of one spot from two angles. A much neater thing to do (in my opinion), would be to put a tilted camera on the outside of spinning ring. Then, try to keep the sat in one position as you take a 360 degree spin around something of interest on the ground. I bet 2 cameras is much cheaper though.
All this... (Score:2, Interesting)
48% of their citizens can't read or write, but they're funding a space program to the equivalent of a few billion U.S. dollars. Amazing. I can only imagine what taxes must be like in India to pay for something so expensive when the per capita income is so low.
Re:Not the distance between the cameras (Score:3, Interesting)
Re:Why two cameras needed? (Score:5, Interesting)
For a parallel example, try to take a picture of the ground from a moving vehicle at 10mph. To get a decently clear and detailed picture, your film speed would have to be high. Now try to get a stereographic image of an ant hill from overhead while moving from a vehicle at 10mph. With one camera you'd have to take fast pictures and move the camera angle without motion blur. As an alternative you could take one picture, change the angle, and pass over the ant hill a second time.
Applying those techniques to satellite imagery doesn't work well. The satellite can't rotate fast enough considering how fast it is passing over a target area. Using 2 passes does work but that unfortunately expends fuel to change the position of the satellite every time. So the lifetime of the satellite is sharply reduced unless it is serviced in space. Rarely are satellites ever serviced. Those that are serviced (Hubble, ISS, etc) have to be extremely important.
Re:Imagine the Possibilities (Score:2, Interesting)
And, for maybe the first time ever, I actually know what I am talking about in a slashdot post, because I studied this crap in college.
Re:Heights? (Score:2, Interesting)
Yes, with accurate clocks, it is possible to determine the location of observer in the space, relative to satellites, quite accurately.
However, for mapping this method is quite inpractical:
To distinguish elevation of every 2.5 * 2.5 meter spot on earth, one would need to move the receiver unit through every spot of that size.
The Earth's surface area is about 4 * pi * (6371 km)^2 = 5.101 * 10^14 m^2. The area of 2.5 * 2.5 m is 6.25 m^2. One would need to move GPS unit to 5.101 * 10^14 / 6,25 = 8.161^13 locations. Good exercise?
On the other hand, something like radio echograph would need energy to get the signal through atmosphere, to ground, and back to the satellite, and therefore is quite impractical for heavy mapping sessions.
Re:power lines? Riiiight. (Score:4, Interesting)
I'm not saying you're wrong about Pakistan though, just that you're wrong about archived maps of India...