Sensors & Software pulseEKKO Product Manual page 158

gaining the data as it can make interpretation difficult (Figure 7-15). In general, soils that are
more electrically conductive (e.g. clays) will require a higher gain compared to soils that are less
electrically conductive (e.g. sand). The type of gain used is what is set under Gain Type in
Plot Options (5.1.10).
7.1.8 Velocity
Velocity is used to convert measured time into accurate depths. The best way to determine
velocity is by using the hyperbola-fitting method, since it is based on data collected in the area.
The current velocity value is displayed on that button beneath the word Velocity.
Crossing linear targets like pipes or cables at a 90-degree (or right) angle produces a hyperbola
suitable for velocity calibration. The value obtained is used to compute a depth estimate of a
target. These depths will be incorrect if the calibration is performed on a target hyperbola
produced at an oblique angle, rather than a right angle.
Once you have a hyperbola on the screen from a subsurface target, press Velocity. The menu
at the bottom of the screen will change (Figure 7-16), giving you the option of specifying a soil
media or adjusting the velocity using the hyperbola-fitting method. These options are explained
below:
•
Media – If there are no targets to calibrate to, and you know the type of soil, press this
button to vary between the following mediums: water, very wet soil, wet soil, moist soil,
Figure 7-15: Varying the Gain
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Collecting Data
GPR