COASTAL WATER CHLOROPHYLL ESTIMATION USING LANDSAT TM 
Maycira Pereira de Farias Costa 
Instituto Nacional de Pesquisas Espaciais 
Caixa Postal 515 - CEP 12201 
Säo Jose dos Campos, SP - Brazil 
ABSTRACT 
This work was performed in Ubatuba, Säo Paulo coast, to assess Landsat 5/TM 
information of chlorophyll concentration (Chla) studies in the ocean. Twenty 
four water sampling stations were determined and the following parameters 
were sampled: chlorophyll a, yellow substance, total suspended solids and 
Secchi depth. TM digital image was prev 
iously corrected and an average of 
nine pixels values of each coordinate point was obtained from TM band 1,2 
and 3. A linear correlation analysis between water parameters and 
it was observed the correlation 
reflectance data was 
applied and 
coefficients between  Chla and TM], 
respectively:0.84, 0.92, 0.86, 0.91 and 0.71. A model to estimate Chla from 
TM bands was determined by usin 
resulting model included TM2 band (R 
a 
TM2,  TM3, TM1/TM2 and TM3/TM2, 
stepwise multiple regression. The 
adjusted=0.84). 
KEY WORDS: Remote Sensing, Ocean water chlorophyll. 
1.0-INTRODUCTION 
The phytoplankton pigments  (chlorophyll 
a) synthetize organic matter from 
inorganic matter by using the solar 
energy. It is responsible for around 95% 
of marine photosynthesis, being the main 
primary productor of the ocean and 
regulating the CO, levels in the 
atmosphere (Perry, 1986). 
The chlorophyll pigment can be used as an 
indicator of primary production level, 
physical oceanographic phenomena, etc 
(Tyler and Stumpf, 1989). 
The conventional sampling methods for 
determining chlorophyll concentration are 
expensive, time consuming. These aspects 
explain the poor spatial distribution of 
the resulting data sets and prevent their 
interpolation and extrapolation. Remote 
sensing data can minimize those time and 
spatial sampling problems by providing a 
synoptic view of the area under study 
(Perry, 1986; Platt and Sathyendranath, 
1988). 
The remote sensor signal results from the 
interection between the solar radiation 
and both water and atmosphere (Kirk, 
1986). 
Pure water presents high absorption in 
the red and infrared region of the 
eletromagnetic spectrum. The water 
spectral response is changed by their 
optically active components such as 
pigments, organic and inorganic matter 
and organic dissolved substances. 
Suspended inorganic matter are the main 
light scatters within the aquatic 
230 
environment. Size, shape and 
concentration are the main factors 
explaining the amount of scattering by 
inorganic matter( Novo et al., 1989). 
Yellow substances are mainly absorbed in 
the short wavelenghts. At high 
concentrations they cause a decrease in 
chlorophyll model sensitivity  (Tassan, 
1988). 
Each phytoplankton pigment presents its 
typical absorption curve. The pigment 
composition varies according to the 
phytoplankton species. Chlorophyll a is 
the main pigment and absorbs at 435nm and 
670-680 nm. The chlorophyll concentration 
in the water can be detected through 
remote sensing techniques since changes 
in its spectral absorption and scattering 
coeficients affect water color. 
Since the early fifties, water color has 
been used as an indicator of water 
components such as chlorophyll 
concentration, inorganic matter and 
yellow substance. In 1972, with the 
Landsat program, there was an increase in 
the use of remote sensing data for 
estimating chlorophyll concentration 
(Sturm, 1980). The poor spectral and 
spatial MSS/Landsat resolution prevented 
the operational use of this sensor system 
for primary production assessment. With 
the advent of CZCS featured to ocean 
color monitoring, there was an increase 
in chlorophyll algorithm development 
(Gordon et al. 1983). With: the CZCS 
discontinuity in 1986, TM/Landsat data 
started to be considered for chlorophyll 
model development (Lathrop and Lillesand, 
1986; Tassan, 1987; Grunwald et al. 1986; 
Braga, 1988; Novo and Braga, 1991, 
Khorran et al. 1991; Ekstrand, 1991). 
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