Kod 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
the worst correlations with the higher values of 
densities as it has highest negative values of Ap. 
Fig. (5) shows measured densities 
versus channel 1 reflectance, where red points 
are below the threshold (Ap=0.01) suggested by 
Rong-Rong Li, et al., 2003. 
A linear fit is run with the accepted data 
and a poor value of correlation coefficient of 
0.59 was found. The fitted line has the equation 
of the form 
Density (mg/lit) = a (Pa)+b (1) 
where a is equal to 4160, b is 106 and Pen 18 
reflectance in channel |. 
Fig. (6) shows the same story but for channel 4 
reflectance. As expected, a better correlation of 
0.77 between density and reflectance in this 
channel was found. The algorithm for channel 4 
data is of the form 
Density (mg/lit) — c (Pens)+d (2) 
with € = 2396 and d = 33.9. 
The minimum density that can be 
detected by algorithm 1 is about 150 mg/lit, 
while this value for channel 4 (algorithm 2) is 
57 mg/lit. This makes algorithm 2 suitable for 
detection of coastal turbid waters as well as 
turbid estuaries, while using relatively low 
spatial resolution sensors such as MODIS 
channel 4(500m). 
  
  
  
  
ao T T T T T 
pu 
5 so} Accepted * : 
> = = - 
— an = N 5 
E S * v A 
2 v "s v. 
"OU yr e a 17 = 
E lier * Dr 
"n 
5 xol 4 + + s © 
; + = 
e : > 
= + 44 * 
= 10D + À à. 4 7 
4- + + 
0 I | | | | 
-0,05 -0023 0 0023 Oùs dors 0.1 
Channel 1 Reflectance 
Fig. (5) Measured density versus reflectance in channel 1 
.of MODIS sensor. 
Larger sediment particles concentration 
did not show a well-defined correlation with the 
total sediment density due to its dependence on 
the tidal state. : 
At the flood situation, more than 95% of 
the sediment particles had diameters more than 
1 micrometer, where in the ebb, less than 75% 
of particles had diameter of lu and more. This 
shows that the heavier particles have resided in 
the ebb situation. The correlation between 
channel 4 reflectance and density of sediment 
particles with diameter more than 1 u was about 
0.81 that shows some improvements. 
The effects of environmental parameters 
on the results were investigated. It was found 
  
  
  
  
an T T T T T 
c y is 
on =, + 
= o 
OL = Accepted ] 
: ter e. 
LA spy + P 
= e + 
D xor e OS * "d 4 
a * 
n = * Va ++ 
5 zl. * e 7 
a bud ht 
* + 
© + 
en . Lt * 
fee. 1 * # + + - 
= . Ka at 
@ #* ++ 
0 I l l l l 
-004 a 0.04 0.08 0.12 0.16 02 
Channel 4 Reflectance 
Fig. (6) Measured density versus reflectance in channel 4 
of MODIS sensor. 
that the visibility had strong influence on the 
correlation coefficients values of the line fit 
between channels 3, 5, 6 and 7, where higher 
visibility | values coincide with higher 
correlation and better prediction of density 
values using channel 4 reflectance. It is 
believed that the atmospheric aerosols are the 
main reason for the poorness of the results, 
while the effect of poor spatial resolution is not 
of lesser importance i. e. each sample represents 
an area of minimum 25 acres. So this sample 
may hardly represent the turbidity of that vast 
area unless we have strong mixing of the water 
in that region. This could be the case at the 
flood or ebb conditions at the vicinity of 
estuaries. 
Due to low wind speed, uniformity of 
temperature and humidity during expeditions, 
1293