Digital Signal Processing Reference
In-Depth Information
Two velocity cross sections were measured at the fixed discharge measuring point in Edko
main drain near exit to lake, and near the bridge on sea exit channel. These sections were
required for checking the inflow and outflow from the lake water body.
Field Work (4)
This field work was conducted in
November 2007,
and the main need was to measure velocity cross
sections at the same locations or earlier measurements, for comparison and check of lake water
balance. The other important measurement was to check the tidal variation of water levels at the sea
exit channel, water levels recording was done for continuous 12 hours inside the exit channel.
5.6.4.
Description and Interpretation of Remote Sensing Data Sets
In situ Water Quality Reference Data
The in situ water sampling and quality measurements were carried out in order to get the true water
selected 26 sampling locations for TSM, Secchi disk transparency, pH, turbidity, depth water
temperature, dissolved oxygen (DO), orthophosphates as phosphorus (PO4), total phosphorus (TP),
Nitrogen compounds as ammonia (NH4), nitrate (NO3) and nitrogen N, 5 days biochemical oxygen
demand (BOD) and chemical oxygen demand (COD).The samples were taken on three days field work
from June 27
th
till June 29
th
.. The main parameters of concern for remote sensing in this study are the
CHL-aorophyll a, TSM, turbidity and Secchi depth.
CHL-aorophyll
a
values were determined by performing analyses on water samples collected at six
selected locations. CHL-aorophyll pigments were extracted in aqueous acetone (90% acetone:10%
water) and analyzed spectrophotometrically (at the Research Center for Oceanography, Alexandria).
Total Suspended Matter (TSM) was defined for all 26 sampling locations. TSM samples were
analyzed in the laboratory using filtration of a known amount of water through a pre-washed, pre-dried
at (103-105
o
C), pre-weighed (~
+
0.5 mg) filter - rinse, dry and reweigh to calculate concentrations in
mg/l. Secchi disk depth readings were done at each sampling location. Secchi disk depth is used as an
important indicator of trophic state and overall clarity of the water. Field turbidity measurements are
made with Submersible portable turbidimeter.
Field Spectrometer
Spectral reflectance measurements were taken with an (ASD) Field Spec Pro-handheld field-
spectrometer which collected reflectance from 350 nm to 2500 nm. A white reference disk was used to
measure incoming radiance for absolute reflectance calculation. The sensor (with a conical field of
view of 25
o
) was attached to a 1 meter long metal bar and extended away from the boat so that shadow
and surface effects from the boat didn't affect the readings. The spectrometer was held roughly 0.6
meters above the surface of the water with a collection time of 25 seconds. Reflectance readings were
gathered at the same locations that the water samples were taken. Days that reflectance were collected
were mostly sunny days so that sky reflectance was minimized. At each sampling location, after a
refrence panel measurement, a number of nine spectrums were taken with a white reference as the
tenth spectrum. A total number of 26 spectral sampling sets were measured during three days of field
work. Spectral measurements of vegetation from both the floating vegetation (water hyacinths) and the
submerged vegetation (potamogeton Pectinatus) were also taken. These measurements were
considered of importance due to the presence of these two types in the lake water and their significant
effect on the signal of spectral measurements.
Figure (5-17)
shows the spectral samples measured at
the different selected locations inside the lake.
Search WWH ::
Custom Search