Tuesday 11 September 2007

ISRO--Remote Sensing

Business India, February 28-March 13, 1994

Remotely sensing profits

Remote sensing is becoming important in corporate planning

Shivanand Kanavi

What do ITC, Tata Tea, Tata Chemi­cals, Indal, Gujarat' Ambuja and fishermen's cooperatives in the west coast of India have in common? They are among the more than 700 users of Satellite Remote Sensing data from the Indian Remote Sensing satellites, IRS-IA and IRS-IB. ITC, the cigarette giant, is using remote sensing to get advance intelli­gence on the tobacco harvest to better pre­dict the price of tobacco when it comes to the market. They have also used it to study sunflower and soybean crops in certain districts of Andhra Pradesh.

Similarly Tata Tea is using it to scout for land that is suitable for tea plantations. Tata Chemicals is using RS to try better watershed management and cropping pat­terns to help the drought-hit villagers around their plant in Mithapur, Gujarat. They are also using it to survey siliceous limestone reserves near their cement plant for possible sourcing. According to Dr Manu Seth, Tata Chem's deputy manag­ing director, they are very interested in developing remote sensing applications to study the post harvest soil condition with respect to nitrogen, potassium and phosphorous content over whole districts. This will help them to advise farmers about the right mix of fertiliser inputs. With their own urea plant coming up at Babrala, UP, this novel application of remote sensing will not only help farmers with scientific information but also help Tata Chern estimate demand and adjust production accordingly. Similarly a num­ber of companies, like Indal and Gujarat Ambuja Cements, are using remote sens­ing for geological prospecting.

The National Remote Sensing Agency at Hyderabad and National Natural Resources Management System and Regional Remote Sensing Service Cen­tres are together making considerable efforts to popularise the technology. They provide satellite data in various forms to Indian users at throwaway prices that are one-third of what a foreign user has to pay but even then internationally they are cheaper than the French, who are their main competitors. They also help in inter­preting it for specific applications. This service is being widely used by various government agencies and a large number of users from the private sector. Among them are 250 fishermen's cooperatives, for whom NRSA provides charts of the best fishing grounds off both the east and west coasts. It has been found that the catch along these recommended routes is at least 30 per cent more than that without the help of such charts.

It is a classic case of a technology developed for war finally being turned around for peaceful developmental pur­poses. After all, remote sensing was pio­neered in the US to locate Vietcong guerrillas hidden in the jungles of Indo­China. Remote sensing is based on the fact that different objects reflect or scatter dif­ferent amounts of electromagnetic energy in different wave length bands.

The electromagnetic spectrum spans wavelengths right from gamma rays to long radio waves. In remote sensing, the most useful regions are visible light, infra red and the microwaves. While passing through the atmosphere, electromagnetic radiation is scattered and absorbed by gases like oxygen, carbon dioxide and ozone and water vapour and dust. The absorption occurs at particular wave lengths whereas certain wavelengths pass through the atmosphere without much attenuation. These are called atmospheric windows.

The reflective or emissive properties of various surfaces at different wave­lengths are called their 'spectral signa­tures'. The spectral signatures combined with spatial variation of these signatures tell us about the size, shape and texture of objects. In case both these fac­tors are the same for two crops, then the temporal variation of reflectance comes to our rescue since for different crops in their growing period it is different. Apart from wavelength, another characteristic of electromagnetic radiation is polarization. The polarisation of reflected radiation also tells us about the object.

Spectral reflectance of vegetation, for example, is quite distinct and plant pig­ments, leaf structure and water content influence it in the visible, near infra red and middle infra red regions. Since vege­tation has maximum reflectance in the infra red, it always appears dark red In RS photographs instead of the usual green that we associate with vegetation. Hence RS photographs are also called 'false colour composites'.

Soil reflectance tells us, about moisture content, amount of organic matter; iron oxide present, relative percentages of clay, slit and sand and roughness of the soil surface. Water reflectance is influenced by its turbidity, etc.

The IRS satellite with a spe­cial camera called the Linear Imaging Self Scanner, based on charged coupled device technology, scans a piece of the earth's surface for radiation in four bands. l) 0.45-0.52 micron: This band is useful for mapping suspended sediments or water quality and various, studies related to coastal region. 2) O.52-0.59 micron: Sensitive towards vegetation discrimina­tion and ferric oxides. 3) 0.62-0.68 micron: Useful for green bio –mass estimation and crop yield studies.

The IRS-IA and IRS-IB carry three cameras. The LISS-I camera provides a picture covering 148.48 km in width with a resolution of 72.5 metres. The LISS-2A and 2B cameras provide a resolution of 36.25 metres and a width of74.24 km. The entire payload including the world class LISS cameras are being make in the Space Applications Centre at Ahmedabad. The data is digitised but requires corrections to be applied for the earth’s rotation and the roll- pitch –yaw motion of the satellite itself.

For furthers analysis of data one needs to know the exact spectral signatures of different crops, soils , terrains, etc, this is called 'ground truth' . The preliminary analysis is compared with actual detailed data from the ground in a small area. For example, if one is looking for cotton acreage under cultivation, probable yield and evidence of pests and disease afflicting the crop, then one needs to correlate satellite data with data from a typical cot­ton growing area.

Remote sensing cannot tell you what is inside the earth but the detailed study of topography can tell you about ground water potential and even probable areas for certain minerals. Recently it has been applied to find probable gold and tungsten bearing regions in Andhra Pradesh. Remote sensing applications in planning are innumerable. Inland aquaculture development, drought monitoring, irrigation an command area development, flood risk zone mapping, urban sprawl, land encroachment, study of forest cover, even damage assessment of forest fires, pipelines and major roads lying are just some of them.

Due to increasing demand for satellite data a whole industry of small scale entrepreneurs has come up around Bangalore and Hyderabad for manufacturing equipment required for data analysis and even consultancies which specialise in data analysis. The skills developed in India in analyzing IRS, Landsat and SPOT data have become so internationally competitive that when France wanted to do a survey on land use to settle subsidy claims of farmers, the contract was given to ISRO. Today, most Regional Remote Sensing Service Centres have become self sufficient indicating the popularity of RS. Besides ISRO has created a wide infrastructure by training over 5,500 spe cialists in the field.

To the credit of ISRO' s satellite tracking, telemetry and command team goes the fact that IRS-lA, whose design life was only three years, has been working like a charm for nearly six years due to astute handling of the satellite from the ground. The IRS-1A and 1B data is top class compared to the American Landsat and the I French SPOT data. In fact, since Landsat- 5 has become old and Landsat—6 launched in 1993 was lost in space (accidents in space do not happen in India alone!) and since IRS data is highly price competitive, compared to the French SPOT, there is tremendous potential to market IRS data in North America. Eosat a US company that is a major in global marketing of remote sensing products, has tied up with Antrix Corporation - set up to market Indian space technology worldwide - to do just that. In fact recognizing ISRO' s experience in building and operating ground stations at Bangalore, Lucknow and Mauritius, Eosat will buy ground receiving systems and data processing software also, from the department of space.

The next generation IRS-l C, to be launched in mid-1995 from Baikanour, Russia, is even more advanced and wjl1 provide stereoscopic data with LISS-3 that has three times higher resolution than LISS-l and 2.The satellite also has a big­ger power pack and, most important, the capacity to record and transmit later. The additional wide field sensor in IRS- 1 C will make it capable of looking at vegetation in an area Once in four days instead of the present 11 days. It is clear that painstaking efforts by ISRO scientists, since the late sixties to learn remote sens­ing data analysis, application develop­ment and even acquiring the capability to fabricate world class remote sensing satellites is finally paying off.