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India Launches World's First Stereo Imaging Satellite
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."
But HIFI stereo, which means it has the highest level of fidelity available. It also sports an 8-track.
crap we hadn't thought of that..
-India
I'm going to assume the satellite designers knew what they were doing and there is some good reason for this.
:-), I'm looking for something a little more informed.)
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
This is just supposition, based on the fact that two cameras on a satellite would not be far enough apart to generate parallax.
Share. Until it becomes uncomfortable. Or at least a little.
Over the summer and last semester I worked in a nano-satellite lab at ASU. The most recent satellite of ours that was launched was Three Corner Sat and one of its primary mission objective was sterio imaging.
g e=3CS
http://threecornersat.jpl.nasa.gov/
http://nasa.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
-- James
... hopefully with Dolby!
--- Attorneys Assisting Citizen-Soldiers & Families -
See who keeps sneaking their $&^%@ trash into your can.
At 2.5 meter resolution? You must have some FAT neighbors.
See what I've been reading.
Getting proper parallax from 620 km is a bit tricky. The cameras would need to be many km apart to get good stereo (31 km camera baseline is equivalent to the parallax that human eyes have at 1 meter).
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.
Two wrongs don't make a right, but three lefts do.
This isn't the first stereographic satellite that's accessible to the general public; that would be MISR - NASA's Multi-angle Imaging Spectroradiometer, built by JPL, with nine cameras pointed in different directions along its direction of travel in polar orbit, ranging from nadir (straight down) to 70 degrees in either direction. Compared to India's new high-resolution satellite, MISR seems very low resolution - 275 meters per pixel - however, it covers the entire surface of the Earth every few days and all of the data is available for free at this resolution, while India's satellite is "targeting"; it only images a particular area when it is programmed to do so. MISR is used primarily to study clouds and aerosols.
To see some 3-D images taken by MISR or some animations of its 9 cameras' views of different scenes, check out their gallery.
Mmm, check out that white pixel laying on the sand colored pixel. Boy, would I like to anti-alias her! Assuming it is a her, and not a surfboard or a trashbag or something. Eh, who am I kidding? I'm not that picky.
1. The Indian economy happens to be the 12th largest in terms of GDP and 4th largest when adjusted for PPP (Purchasing Power Parity). 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) pursued a pretty widespread (and largely non-military space program) since the 60's. From this relevant Wikipedia article:
# 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.
An Indian-American Hindu committed to non-violent thought/speech/action alarmed by the global explosion of radical Islam
And a nitpick which will hopefully bring this post back on topic - the average literacy you mentioned is wrong. It is 64.8% 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.