Malaysian Tiungsat-1 Imagery for Water Quality Mapping

M. Z. MatJafri, K. Abdullah, H. S. Lim
School of Physics
Universiti Sains Malaysia
11800, Pulau Pinang.
Tel: 604-6577888 Fax: 604-6579150
E-mail: khirudd@usm.my and mjafri@usm.my

1. Introduction
Suspended matter deposited in reservoirs reduces their storage capacity and suspended material reduces the light penetration in water, thus minimizing the fish production (Choubey, 1998). The major factors affecting surface water quality are suspended sediments, chlorophyll, nutrients and pesticides. The standard traditional mapping and monitoring techniques have already become too expensive compared to the information achieved for environmental use. A solution could be to optimize our efforts and more frequently base our surveillance on remote sensing techniques to improve the information content and limit the cost (Ostlund 2001). Remote sensing offers potentially a significant source of information and methods are being developed for operational large-scale monitoring of water quality (Koponen et al. 2002).

In this study, satellite scene from Tiungsat-1 was used for water quality mapping around Penang Island. This preliminary study indicates the possibility of using Tiungsat-1 satellite image for monitoring coastal water quality.

Multi-spectral algorithms were used to determine the TSS concentration on the surface of seawater. Various algorithms were also tested and the values of their correlation coefficient (R) and root-mean-square deviation (RMS) were compared. The proposed algorithm was used to generate the water quality map. Finally, the digital image was geometrically corrected to produce a water quality map.

2. Study Area
The study area is located between latitudes 5° 12’ N to 5° 30’ N and longitudes 100° 09’ E to 100° 26’ E as shown in Figure 1. The Tiungsat-1 satellite image captured on 17 March 2001 was used in the present investigation. The water sample data collected within the region of interest were available for calibration of the quality algorithm.

3. Optical Model of Water
A physical model relating radiance from the water column and the concentrations of the water quality constituents provide the most effective way of analyzing remotely sensed data for water quality studies. Reflectance is particularly dependent on inherent optical properties: the absorption coefficient and the backscattering coefficient. The irradiance reflectance just below the water surface, R(l), is given by Kirk (1984) as
R(l) = 0.33b(l)/a(l)           (1)

where
l = the spectral wavelength
b = the backscattering coefficient
a = the absorption coefficient




Figure 1. The location of the study area
The inherent optical properties are determined by the contents of the water. The contributions of the individual components to the overall properties are strictly additive (Gallegos and Correl, 1990).

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