CJReport

REMOTE SENSING APPLICATION I N NEPAL

Bhesh Thapa
GIS Engineer,
Farrer Consulting,
www.farrerconsulting.com
Email:bheshthapa@yahoo.com

Abstract

Remote Sensing is the process of collection data about objects or landscape features without any physical contact. Most Remote Sensing is performed from orbital or sub-orbital platforms using instruments which measure electromagnetic radiation reflected or emitted from the terrain. The air craft and satellites are used to observe the earth as a means of platforms to acquired remote sensing data. At first, the imagery of Nepal took by Earth Resource Technology Satellite (ERTS) and later satellites in 1972, which was extensively used as map substitute. But the use of remote Sensing started in 1933 by photography of Mt. Everest areas and satellite remote Sensing developed since the 1980s in Nepal. The department of Forest, Survey, Mining and Geology and other international organization (ICIMOD), has been used remote sensing data for planning, monitoring and evaluation of development projects. The use of satellite data (IKONOS-1m resolution and IRS) is in initial stage at department of survey, Nepal. Actually, the satellite remote sensing is a scientific tool monitoring the earth resources providing temporal data for cost effective and quick scientific decision.
Keywords: Resolution, imagery, aerosol, Remote Sensing, Satellite, radar, geometric, radiometric. spectral, azimuth.

Development & Application of Remote Sensing

The development of Remote Sensing technology was started by the establishment of National Remote Sensing Centre (NRSC) in 1981 in the joint cooperation of His Majesty’s Government of Nepal and USAID. The main objective of the NRSC was to bring multi-disciplinary scientists to work together for generating useful information for national development. This was the first technological institute established in Nepal, focused on remote sensing application. During 1985 to1989 the NRSC was getting some funding from international agencies (FAO,GTZ,JICA &UNSP) to installed equipments, besides numbers of trained and qualified multi-disciplinary scientific staff, such as forest specialists, agriculturalist, soil scientists, meteorologists, geologists, cartographers, remote sensing officers and photogrammetrist,etc .In 1984,the NRSC organized fifth Asian Conference on Remote Sensing. The conference was concentrated on problems in Remote Sensing, to exchange academic and technical information and to promote operational applications in the region. While the NRSC was merged under the Forest Research and Survey, Ministry of Forest and Soil Conservation, the specialists of Remote Sensing joined into different organizations the area of FORESC is limited to forestry. As we know the Remote Sensing technology has been started by the department of forestry in Nepal.
The forest Survey and Research Office have been using aerial photographs since 1967 for district wise forest inventories. After merged of NRSC, remotely sensed data, such as; satellite imageries (LANDSAT TM & IRS LISS 111)along with the aerial photographs are being in use for national forest inventories using Geographic Information System (GIS).Since 1990s,Forest Resource Information System (FRIS)project, funded by Finnish International Development Agency (FINNIDA) was instrumental in using the satellite data for forest resource information.
The main achievements of the NRSC were as follows:
• Estimation of forest area on national basis,
• Study of natural resources of Gulmi district for appropriate management and planning,
• Arun watershed feasibility study for hydropower production and irrigating purposes,
• Hydrological and geological mapping of Bagmati Watershed for developing soil conservation strategy,
• Study of snowline survey and run off predicton,
• Study of Marshyangdi watershed area for the possibility of hydropower development,
• Organization of seminars/trainings/workshops and exhibitions on national and international basis,
• Yield study of winter crops of Bhaktapur district, etc.
In Nepal, aerial photographs have been used for three decades for mapping and monitoring the natural resources. Forest resource mapping, resource assessment and national level forest area estimation are the main application of satellite remote sensing in Nepal. Department of Survey, NEPAL, is trying to update the base map of Kathmandu city using IKONOS-1 meter resolution satellite data.

Technical difficulties and constraints

As we know the Nepal is a mountainous country, so the satellite image contains considerable shadow in winter compare to summer due to low sun elevation angle. This means total loss of information of surface. The summer is the rainy season and most of days are covered by cloud, even though less than five percent cloud can be accepted which depends on the purpose of data use. But, at this condition can be used active sensor data or radar image. The active satellites are time and season independent so we can get information at any time and season bit need more skilful interpreter to extract the information. As a mountainous country, Nepal, the terrains are more or less hilly; with low sun elevation angle. Rugged topography causes a lot of variation in spectral response and considerable shadows. These factors create various types of errors in image data which we called radiometric and geometric errors. The geometric distortion arises from the earth curvature, plate form motion, relief displacement and non-linear ties in scanning motion. But the radiometric distortion arises form the sensor sensitivity, sun angle, topography and atmospheric scattering. When a sensor mounted on an aircraft or spacecraft observes the reflected energy of earth surface the observed energy does not coincide with the energy reflected form the same object observed from short distance. This is due to sun’s azimuth and elevation, atmospheric conditions such as; fog, aerosols, sensor’s response etc; which influence the observed energy. Therefore, in order to obtain the real reflectance, that radiometric and geometric errors should be corrected. Normalized Differentiate Vegetation Index (NDVI) is one of them in case of forest monitoring and change detection study.
In rectifying an image of the hilly area, a small error is always resulted unless there are accurate and enough control points. The enough control points are necessary to minimize the positional errors.
The following organizational difficulties and constraints are responsible for the application of Remote Sensing in Nepal:
• Lack of co-ordination agency in the country which is responsible for data acquisition and supply to the entire data user,
• Dependence on foreign donors for satellite data,
• The remote Sensing data is expensive (high resolution) using the limited government resources,
• Lack of sensitivity and knowledge of remote sensing in policy maker,
• Staff transfer and political instability is another problem for the sustainable use of the technology,
• Lack of enough software, hardware, data quality and skill manpower.

Conclusion
Remote Sensing is a source of data which is multi-disciplinary, can be applied for any research work. The satellite can take a large area in one scene and can get frequently as well as cost effective and time independent which is not possible by aerial photography. Indeed, the application of satellite remote sensing and GIS in Nepal is a wide scope for natural resource mapping and sustainable development. As a mountainous country it is difficult flying aircraft frequently as well as expensive acquired aerial photography or resource monitoring and management.

Reference:
Thomas M.Lilles and Ralph W.Kiefer 1999: Remote Sensing and Image Interpretation.Now York,Singapore and Toronto: by Jon Wiley and Sons Publication.
Floyd F.Sabins.JR.1980: Remote Sensing Principles and Interpretation.New York Published: by W.H Freeman and Company,USA
Department of Forest,Government of Nepal,Babar Mahal,Kathmandu.