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Remote Sensing : Country Report – Sri Lanka

N. G. R. Fernando
Deputy Surveyor General, Sri Lanka


1. Introduction
1.1 Sri Lanka is a predominantly agricultural country.
Five million acres of its sixteen million acres are under cultivation, the major crops being paddy, tea, rubber and coconut. The island has two distinct climatic zones. The Wet zone in the South West Quarter of the Island is thickly populated and is influsenced by the South West Monsoon winds. The Dry zone covering the northern and eastern sections of the island gets rain mostly during the North-Eastern Monsoonal months. This is the region which had supported an ancient civilization based on paddy cultivation using water during the dry season from a series of both small and large man made reservoirs called tanks. These tanls have subsequently got into disuse and, as a result, this region during a long period was left abandoned. However, during the last 50 years restoration of these tanks and subsequent colonization of these areas have been undertaken.

2. Mapping
2.1 The country is well mapped. It had a series of comprehensive topographical maps on the 1/63,360 scale from the beginning of the century. Air survey activities were introduced into the country in 1956 when the country obtained a full cover of air photography on the 1/40,000 scale. The National Survey Department is well equipped to handle all types of photogrammetric work and all ground survey activities. It has now commenced work on the production of two series of maps one on the 1/50,000 scale and the other on the 1/10,000 scale, to form base maps for agricultural and other development activities.

3. Remote Sensing Activities
3.1 The existing maps and photographs have been used throughout the years with supplementary land surveys for studies required for development projects. However, since of late the need for recording information changes at frequent intervals was beginning to be felt. It has been felt that remote sensing techniques would provide the answer for part of these needs. With this in view activities in this direction were commenced about six years ago.

3.2 Mention should be made of U. S. Aid assistance received for this purpose in 1975. In 1976 technical assistance was received from Environmental Research Institute of Michigen (ERIM).

The technical approach of this project called for development of incountry capabilities for normal and simple digital processing of Landsat Data and evaluating various types of satellite imagery for application to crop and water resource assessment. While extensive normal image analysis was performed using standard EROS data center Products, digital processing was perceived as the key to quantitative agricultural surveys in a country with small field sizes such as Sri Lanka. Under this US AID assistance the following specific activities were performed:-
  1. Acquisition of image analysis equipment.
  2. Obtaining imagery and supplies.
  3. Modifications and adaptation of LIGMALS software (LANDSAT nteractive Gray Map and Land Slicing systes developed at the University of Michign) for operation on a locally available computer.
  4. Advanced digital processing of Sri Lanka
Data carried out in the U.S. and evaluated in Sir Lanka.

5. Local staff visiting agencies carrying out activities in this field in Washington D.C., Ann Arbor, West Lafayette, Sioux Falls and Bangkok

A working group formed within the Survey Department consisting of personnel experienced in Photogrammetry, Computer Programming, photo Laboratory Techniques and Photo Interpretation formed the fore runner of the Centre for Remote Sensing.

3.3. Mention should also be made of the assistance received in 1978 from the Swiss Directorate for Development Co-operation. This project has been renewed for a further period of two years from 1980 a team of Swiss Experts in now working in the country with local officials. A center for Remote Sensing has been established in the Survey Department. A field test area covering two administrative districts which form part of a vast development area has been selected for these studies. The approach is to find suitable and simple procedures and techniques of obtaining the required information regarding present land use and changes of same using satellite imagery supplemented by aerial photographs, topographical maps and field visits. Equipment obtained from Switzerland has been installed. These include a unit to process satellite imagery. A limited under of staff at different levels have been freshly recruited or obtained from the regular cadres of the Survey Department and have been or are being trained. This training included visits to the National Remote Sensing Agency (NRSA) Station at Hyderabad as well as Japan. Satellite Imagery is now obtained from NRSA.

4. Applications

4.1. Prospective user agencies in the country have been briefed of the potentialities of Remote Sensing Techniques. Different Aspects of this subject have been introduced to the land survey and other professionals through discussion groups, seminars and technical journals.

4.2. One of the main tasks will be an attempt to produce a series of maps showing the present land use to eb used by the land use policy planning Division of the Ministry of Lands and Land Development. An attempt will be made to monitor locations of forest clearings with a view to arresting large scale deforestation. Such information will be used by the Forest Department in its regular activities.

4.3. One other very important aspect will be an attempt to monitor the extents under paddy cultivation durng the different seasons for statistical purposes to be used by the Ministry of Agricultural Development and Research, the Department of Census and Statistics and other similar Agencies. So far the required information had been obtained either from cultivatior’s estimates or from estimates ppepared from sample studies. Both these have not been able to provide sufficiently accurate results. Remote Sensing Techniques are expected to provide much closer approximations.

4.4. Other prospective users such as the Geological Survey Department and the Coast Protection Division of the Ministry of Fisheries are also following the progress that is being made by the center for Sensing.

5. Conclusion
5.1 Hence it can be said that there is a great interest show towards these techniques by the professionals as well as the user agencies and that steady progress is being made by the Centre for Remote Sensing in it’s different activities.