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India Launches World's First Stereo Imaging Satellite
Posted by
CmdrTaco
on Wed May 04, 2005 02:15 PM
from the zombies-look-so-real-in-three-dee dept.
from the zombies-look-so-real-in-three-dee dept.
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."
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Not just stereo (Score:5, Funny)
Re:Not just stereo (Score:3, Funny)
Tech support... (Score:3, Funny)
Re:Tech support... (Score:3, Funny)
I see you're using the term "humor" quite loosely.
What? How far apart... (Score:3, Interesting)
Parallax by pointing (Score:5, Insightful)
Instead, I suspect that the parallax is achieved by having two cameras that point slightly different angles. One points down and forward along the track of the satellite, the other points down and backward. Thus, as the satellite passes overhead, the same spot on the ground is seen by the two cameras in succession from different parts of the orbit.
For purposes of get topo data on fixed objects, its more than adequate. Given that the satellite is moving about 8 km/sec, it traverses the needed baseline for stereo in only a few seconds. This is not enough time for the scene to have changed that much.
Parent
Heights? (Score:3, 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
No (Score:3, Informative)
Re:Heights? (Score:3, Insightful)
Yes.
How would a picture be more accurate?
Well, among the most accurate topographical maps available are from the Shuttle Radar Topography [usgs.gov] mission, which gave us the entire earth at roughly 30-m resolution, with a height precision of about 16 meters.
India's new satellite has 2.5-meter resolution, and its vertical accuracy after proper stereoscopic matching would be of the same order of magnitude so
I don't get (Score:4, Interesting)
Re:I don't get (Score:5, Funny)
-India
Parent
Re:I don't get (Score:4, Insightful)
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Re:I don't get (Score:4, Funny)
Any ham-radio enthusiast can make one of those. A stereographic mapping satellite, on the other hand, is engineer-grade.
Parent
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
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
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.
Parent
Re:Why two cameras needed? (Score:3, Funny)
You must be new here.
Re:Why two cameras needed? (Score:4, Informative)
Everyone who posted before this is encouraged to be a little more careful providing answers in the future. (All four that I can see are not only wrong, in the sense they don't contain the correct explanation, but also in the sense that they contain serious technical errors.)
Parent
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.
Re:Not the distance between the cameras (Score:4, Informative)
Makes sense, though. According to the article, the orbit is at 620km. To obtain 1.0 degrees of stereo separation would require cameras placed 10.8km apart.
Parent
Re:Not the distance between the cameras (Score:3, Informative)
The curvature of the surface is not relevant to the calculation, thus neither is the radius of the earth. To consider the extreme cases, the surface could be absolutely flat (radius infinite), or it could be a point (radius zero). Either way, your two cameras are still 620km away from that surface. The object is still at some other distance which
Re:Not the distance between the cameras (Score:3, Funny)
Re:Not the distance between the cameras (Score:3, Interesting)
These Indian Guys (Score:3, Funny)
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]
Ugly Rumor (Score:3, Funny)
I'm kidding!
I'll Wait For Quadrophonic Images ... (Score:5, Funny)
power lines? Riiiight. (Score:4, Insightful)
Um...right. Like decades if not centuries of maps can't help there. Besides, I would think that in a country as large as India, they'd be focusing on localized power generation.
Sorry, but this sounds like a really lame excuse for lobbing a satellite up there to spy on Pakistan, with a happy-go-lucky PR spin so the average citizen thinks "oh, another satellite that will be useful!" Yessir, routing power lines.
Not like the US hasn't done the same thing- the majority of shuttle missions were for either admitted, or "disguised-as-scientific-experimentation" military satellites.
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...
Parent
Camera motion used to generate stereo pairs (Score:4, Informative)
Largest Cluster of RS satellites? (Score:3, Informative)
EOS/Terra/MODIS http://modis.gsfc.nasa.gov/ [nasa.gov]
Landsat ETM+ http://landsat.gsfc.nasa.gov/ [nasa.gov]
Landsat MSS (yes still going)
AVHRR http://daac.gsfc.nasa.gov/data/dataset/AVHRR/ [nasa.gov]
GOES http://www.goes.noaa.gov/ [noaa.gov]
ASTER http://asterweb.jpl.nasa.gov/ [nasa.gov]
Not to mention US based commercial satellites:
IKONOS http://www.spaceimaging.com/ [spaceimaging.com]
Quickbird URL:http://www.digitalglobe.com/
Somebody is conflating ... (Score:3, Interesting)
Not first stereographic, but first hi-res stereo (Score:5, Informative)
To see some 3-D images taken by MISR or some animations of its 9 cameras' views of different scenes, check out their gallery [nasa.gov].
Also launched a ham satellite: VUSat (Score:4, Informative)
NRO (Score:3, Informative)
Re:NRO (Score:3, Informative)
Check out the cameras [nro.gov]
Don't know when the birds got stereo capability, but the first photos were returned in 1960 [nro.gov].
Re:How many military satellites already do this? (Score:3, Informative)
http://www.madsci.org/posts/archives/2004-09/10940 49193.Ph.r.html [madsci.org]
I've exchanged email with NOAA about hurricane photos and have been told that some of them are inface ISAR radar images that have been colored.
The blurb there for the story sounds like a Press Release there from Mr Nair, chairman of the Bangalore-based Indian Space Research Organisation (Isro).
Re:Imagine the Possibilities (Score:5, Funny)
See who keeps sneaking their $&^%@ trash into your can.
At 2.5 meter resolution? You must have some FAT neighbors.
Parent
Re:Imagine the Possibilities (Score:4, Funny)
If they could only get a little better resolution, I can imagine they could pull in some cash by taking pictures of nude beaches. You would think that by now the first thought with new tech would be, "how can I use this for porn?"
Parent
Re:Imagine the Possibilities (Score:5, Funny)
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Re:Imagine the Possibilities (Score:3, Informative)
Don't get too excited. The process of extracting 3d depth from a pair of 2d pictures is shockingly more difficult than one would initially expect. Given the 2d positions of the same point in both cameras, it is trvial to find the 3d depth, but in practice the problem of finding the corresponding points is extremely difficult. (It is called the 'correspondence problem' and can justifiably be called the holy grail of the field of Computer
Re:All this... (Score:3, Informative)
India has a population of 1,065,070,607 [google.com] whereas the US has a poulation of 293,027,571 [google.com]
52% of 1,065,070,607 is 553,836,715 and 97% of 293,027,571 is 284,236,743. That m
Re:All this... (Score:3, Informative)
Google shows their budget to be somewhere around $3.3 billion US over 5 years or about $650m.
Given nasa's budget of $16 billion US, and the US's population of 300m, per capita income of $30k VS india's 1b population at $3k per capita...
The amount of tax [compared to per capita income] needed to fund the space programs are nearly identical. (around
Re:All this... (Score:3, Insightful)
I had enough of "but there are starving people there" comments about India. India is a developed nation as far as intellectual capital is concerned. If the Indian government completely ignored this segment of the population, they would simply emigrate.
Re:All this... (Score:4, Informative)
And a nitpick which will hopefully bring this post back on topic - the average literacy you mentioned is wrong. It is 64.8% [censusindia.net] according to the 2001 census. The number you gave was for 1991. 14 years can make a lot of difference in a country like India, even given its huge population.
Parent
Re:All this... (Score:3, Informative)
Since you asked for a clarification.... (Score:5, Insightful)
1. The Indian economy [wikipedia.org] happens to be the 12th largest in terms of GDP and 4th largest when adjusted for PPP (Purchasing Power Parity [wikipedia.org]). I quote from the Wikipedia article:
With a GDP of 568 billion (B$) ($3.096 trillion (T$) at PPP) India has the world's 12th largest economy (and the 4th largest when adjusted for PPP). However, the large population means that per capita income is quite low. In 2003 the World Bank ranked India 143rd in PPP per capita income and 160th in real terms, among 208 countries and territories.
2. India has (through the Indian Space Research Organization [isro.org]) pursued a pretty widespread (and largely non-military space program) since the 60's. From this relevant Wikipedia article: [wikipedia.org]
# 1962: Indian National Committee for Space Research (INCOSPAR); formed by the Department of Atomic Energy, and work on establishing Thumba Equatorial Rocket Launching Station (TERLS) near Trivandrum began.
# 1963: First sounding rocket launched from TERLS (November 21, 1963).
# 1965: Space Science & Technology Centre (SSTC) established in Thumba.
# 1967: Satellite Telecommunication Earth Station set up at Ahmedabad.
# 1972: Space Commission and Department of Space set up.
# 1975: First Indian Satellite, Aryabhatta, launched (April 19, 1975).
It's also fruitful to note that India was a British colony till 1947. IMHO, starting a space program in about 1.5 decades after gaining independence is a laudable achievement. The major problem which India faces today is it's large population, which pretty much negates all the economic advances, and causes it's perception as a "thirld world country" to continue.
It is also worth noting that India seems to be spending substantial amounts of money to improve it's people's lot and advancing education, science and research, rather than spending it instead on aggressive military tactics, which seems to be the trend nowadays. If you read up the history of the nation, you'll see that it's one of the few countries that has never pursued invasion/colonialism, and has instead been frequently invaded by conquerers (Mughals, British, etc) who looted the wealth of a formerly rich region and left it in a state that it's trying to dig itself out of now.
PS: Posted this because I perceived a derogatory slant in the Parent's use of the term "third world country". I find the practice of using wealth to rank nations (especially so when used to diss poor nations) quite abnoxious. I have nothing against using the term in a scientific/neutral sense.
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Re:Need clarification (Score:4, Informative)
India keeps losing it best people to the US but now slowly more and more people are staying back and using their brains to run ISRO and DAE (department of Atomic Energy) instead of enriching the shareholders of IBM and Microsoft.
There is great emphasis on tech in India . Engineers are much more respected in society than doctors or lawyers in contrast to the US so a lot of the top brains go to Engineering.
Parent
Re:India Can't Afford This (Score:3, Insightful)
I'm going to act as if the poster was sincere and not a troll, therefore deserving of a thoughtful answer.
Every government is faced with the challenge of balancing the short term needs of the impoverished with the long term obliga