Integration of Remote Sensing and GIS Techniques to Study the
Relationship Between Vector Borne Disease and Vegetation
Cover: A Case of Malaria Chanthaburi Province of Thailand
Site Description
Chanthaburi province is a malaria endemic area of Thailand, located along the Thai-Cambodian border (Fig. 2). It is about one-third covered by forest with rice paddy fields representing about 30% and Para Rubber/orchard representing about 20% of the land use covered. The geographic environment comprises of mountains, hills, undulating land plain and coast land. The climate is tropical monsoon with the rainy season from April to October/November, with an average of 2,915.10 mm/year. Average temperature ranges between 26.02 and 29.56 degree Celsius.
Fig. 2 Location of Study area.
Data Base and Data Analysis
Normalized difference vegetation index (NDVI) were calculated for NOAA satellite coverage's of Thailand for 10 dates between December 1992 and April 1993 by using a ratio of the visible band 1 and the near infrared band 2. These data were then composite by selecting the highest NDVI for each grid cell location. These data have been used as thematic raster base maps for displaying malaria incidence by provinces and by district. This data also has been used to determine forest cover in provinces of Thailand using unsupervised classified of raster images to create vector maps of forest cover (TNT mips, 1996). Correlation between area of forest cover and malaria incidence by province have been made (Fig. 3).
Fig. 3: Correlation between percent forest cover and malaria.
The processed calculated malaria incidence data had been incorporated in to the GIS database for each district of Chanthaburi. This data includes species of Plasmodium and origin data for malaria cases. The malariometric survey has been started in Chanthaburi Province by monitoring cases at district malaria clinics.
The land use map of Chanthaburi provinces prepared at 1:500,000 by the Land Development Department, Ministry of Agriculture and Cooperatives Thialand 1986 and 1990 were digitized. These maps for 1986 and 1990 were originally prepared from interpretation of Landsat 5 MSS and TM, respectively. These maps has been digitized using ARC/Info software. The total area for each land-use type in each district has been calculated.
Thematic maps of malaria incidence using the land use maps of Chanthaburi in 1986 and 1991 as the base maps have been created. The 1985 malaria data is displayed on the 1986 vegetation image data in which it has been found that the available existing 1985 maps were not consistent and appeared to be unreliable.
LANDSAT TM image of February 1995 has been classified to produce the land use map of the province. Land use maps included five classes. ERDAS software was used as the image processing tool .Unsupervised classification of the image was performed by defining 20 classes with 2,3 and 4 bands of TM. Intensive field verification was performed by the use of the Global position system (GPS) instruments and a GPS camera for the unsupervised image and for the training sample.
