Environmental Engineering Reference
In-Depth Information
Table 1.2
Continued
Digital optic
imaging
Pressure
difference
Technology
Turbidity (bulk optics)
Laser
Hydroacoustic
Measurement
metric basis
to routinely
compute
mean
cross-sectional
values
Calibrated to SSC
from physical
samples in mass
units
Calibrated to SSC
from physical
samples in mass
units
Calibrated to SSC
from physical
samples in mass
units; PSD in 32
size classes;
volume SSC,
converted to
mass SSC if
density known
Calibration
may be
unnecessary;
PSD in 32
size classes;
volume SSC,
converted to
mass SSC if
density
known
Calibrated to
SSC from
physical
samples in
mass units
Calibrated to
SSC from
physical
samples in
mass units
Calibrated to SSC
from physical
samples in mass
units
Calibrated to SSC
from physical
samples in mass
units. If PSD, by
variable response
to selected
frequencies
Ancillary
measurements
None
None
Depth and water
temperature
Depth, ambient
velocity,
water
temperature
None
Stage
Index velocity.
Depth if oriented
down
Index velocity.
Depth if oriented
down
Reliability and
robustness
Optical window
may foul,
causing signal to
drift with time.
Sensor may
saturate at
larger SSC
Optical window
may foul,
causing signal
to drift with
time. Sensor
may saturate at
larger SSC
Requires
anti-fouling
device or
bioblock. Sensor
may saturate at
larger SSC; PSD
larger than
0.5 mm not
included in
calculations.
PSD larger than
0.5 mm not
included in
calculations.
Accuracy may
decrease
with
window
fouling;
software
will correct
for this
within
yet-
undefi ned
limits
Low SSC data
unreliable;
veracity of
higher SSCs
unresolved
More or less
unaffected by
fouling. Responds
almost solely to
entrained
sediment
More or less
unaffected by
fouling. Responds
almost solely to
entrained
sediment
