Channel Master CM-6001 Specifications download pdf (Page 130)

Channel Master Operation Manual

page 124 RD Instruments

Doppler Velocity Log (DVL): An instrument designed to measure the ve-

locity and elevation of a moving platform with bottom tracking. Most

DVLs will switch to measuring velocity relative to the water when the bot-

tom is out of range.

DVL: Doppler Velocity Log.

------ E ------

Earth Coordinates: Profile data is reported in an orthogonal coordinate

frame as referenced to the Earth (East, North and Up). “North” can mean

magnetic or true, depending on the heading input.

Echo Intensity: A key quality control parameter, echo intensity is a meas-

ure of the signal strength intensity returned to the transducer. High echo

intensity can show solid targets (e.g. a boundary, obstruction or fish), while

low echo intensity can show insufficient scatterers or the limits of profiling

range for the environment.

Edge Estimate: When measuring river discharge with an ADCP it is not

possible to measure to zero depth at the banks of the river. The flow

through this unmeasured area must be approximated in order to obtain an

accurate estimate of the total discharge.

Ensemble: A group of measurements (pings) considered together. An en-

semble is usually the average of the individual measurements, and has a

higher precision than any individual measurement.

Error Velocity: A key quality control parameter that derives from the four

beam geometry of an ADCP. Each pair of opposing beams provides one

measurement of the vertical velocity and one component of the horizontal

velocity, so there are actually two independent measurements of vertical

velocity that can be compared. If the flow field is homogeneous, the

difference between these vertical velocities will average to zero. To put the

error velocity on a more intuitive footing, it is scaled to be comparable to

the variance in the horizontal velocity. In a nutshell, the error velocity can

be treated as an indication of the standard deviation of the horizontal veloc-

ity measurements.

------ F ------

Fish Detection Threshold: Used to identify and mark as bad any velocity

measurement that was potentially contaminated by a fish (because fish are

generally not passively following the flow). It is a flag on the maximum

allowable value for the measured echo intensity return.

Frequency: The number of wave crests passing a given point per unit time.

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Channel Master CM-6001 Specifications Page 130