The use of coarse spatial resolution AVHRR HRPT data was found to be extremely useful for large scale assessment and monitoring of major land cover types of Thailand. The methodology developed and used in other countries in the region well demonstrated its usefulness in Thailand, as well.

Major land cover types such as forests, croplands, paddy rice (irrigated) and waterbodies were discerned from the satellite data used. Deciduous and evergreen forests were not able to discriminate with reasonable accuracy particularly in the north where a complex of deciduous and evergreen forests exists. Mangrove forests, occurring in sporadic patches are not exhibiting distinct signature in the AVHRR data. Persistent cloud cover in the Peninsula was another major problem. The availability of cloud free data and its use in the study would definitely be an advantage.

Through the time series analysis of 1985/86 and 1992/93 satellite data, change analysis was performed. Areas undergoing major land cover transformations ("hot spot") were identified. Forest area was found to be most affected which is changing to non-forest areas mainly to agricultural lands. Due to various policy measure to combat deforestation, forest area of Thailand is decreasing at the decreasing rate. Other changes are insignificant.

Analysis of AVHRR data source in conjunction with GIS helped to correct the classification errors. The GIS database was found to be very useful in analysing the AVHRR data. For in-depth understanding of the nature and mechanism of forest cover transformation, detailed investigation using high resolution satellite data is recommended. Further analysis of NOAA data on a biannual basis is recommended to rectify the classification errors and also for the refinement of the methodology.
 
 
References
 
GAIA, 1995. GAIA : A Multi-Media Tool for Natural Resources Management and Environmental Education. Environmental Software and Services, Austria.

Gutman, G.,1991. Vegetation Indices from AVHRR : An Update and Future Prospects. Remote Sensing for Environment. Vol. 35, pp. 121-136.

IGBP, 1992. Improved Global Data for Land Applications: A Proposal for and IGBP-HDP Core Project. The International Geosphere-Biosphere Programme (IGBP), Global Change Report No. 24. IGBP, Stockholm.

Klankamsorn, B., and T. Charupat., 1994. Deforestation in Thailand. Royal Forest Department, Bangkok, Thailand.

Onchan, T., 1993. A Land Policy Study. The Thailand Development Research Institute Education, Bangkok, Thailand.

Ongsomwang, S., 1995. Forest Resources Monitoring Systems in Thailand. Paper Presented at the Expert Consultation on Forest Resources Monitoring Systems, FAO/RAPA, Bangkok, Thailand.