Digital Signal Processing Reference
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the hydrodynamic model the calibration target was water levels at specific measured points. The
comparison of the TSM patterns between the model and the image was used to set the validation target
parameter from the remote sensing images (MODIS time series) based on the sensitivity of TSM
spatial distribution to velocity patterns. The average correlation coefficient of 0.73 is considered valid
for the spatial comparison between the two datasets taking into account the effect of mixed pixels and
calibration accuracy of the received MODIS raw images. This spatial correlation indicates that the
TSM patterns of the model and the images are positively correlated and follow the same trend.
Consequently we can consider the hydrodynamic model to be a good performing model that can be
used in the next steps of calibration and validation.
8.5.4.
Developing TSM Time Series dataset from TSM-MODIS concentration maps
The developed correlation formula shown in
Equation (8-5)
was tested on the sampling points of open
water areas and applied on the set of 14 images covering the modelling period. Focused analysis was
done on the image acquired on June 28
th
where the field measurements were taken, to compare the
values from the
in-situ
measurements, the image and the model. The image reflectance values were
converted to suspended sediment concentration values.
Figure (8-19)
shows TSM map using the
developed exponential relation.
CHL-a = 4.0176 EXP (32.107B1)
(8-5)
Where:
CHL-a = chlorophyll a concentration (mg/l)
B1= MODIS Band 1 (665 nm)
Figure (8-19): MODIS TSM concentration map June 28
th
applying the developed algorithm
In order to compare the model and image patterns, the ROI was applied to both maps,
Figure (8-20
a
and
b
)
. The two maps were stacked for correlation analysis. The resulting correlation coefficient of
0.89 shows high spatial similarity. On the other hand, comparing of the two profiles taken from both
maps shows that the model is underestimating the concentration values,
Figure (8-21)
.
Selected
locations for pixel to pixel comparison are shown in
Figure (8-22)
including the model predicted TSM
concentrations on 28
th
of June, 2006.
Figure (8-20): (a) TSM concentration map applying the developed algorithm (left) and (b) TSM concentration
map predicted from model
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