User's Manual

Appendix B: GPR Signal Processing Artifacts pulseEKKO PRO
B-2
Figure B-2: Display of a single data trace (left) and data section (right) with the low frequency WOW component present. Com-
pare these plots to the figure below where the WOW has been removed with the DEWOW high pass filter.
Turn the DEWOW filter off to see this low frequency component of the data when plotting the data with
Windows-based software.
Dewow Filter
With this wow usually being present, it is common practice that GPR data is high pass (DEWOW) filtered.
DEWOW is a high pass filter optimized to pass the transmitted signal spectral peak for the specific antenna
center frequency with fidelity and suppress the low frequency wow in the data. The wow is removed from
the data by applying a running average filter on each trace. A window with a width the same as that of one
pulse width at the nominal frequency is set on the trace. The average value of all the points in this window
is calculated and subtracted from the central point. The window is then moved along the trace by one
point and the process is repeated.
In the initial software releases, this high pass filtering was integral to all of the plotting and display
programs. As a result the user was, in many situations, unaware of this wow or low frequency component
in the data. The raw recorded data, however, always retained this information.
Figure B-3: Display of a single data trace (left) and data section (right) where the Wow seen in the figure above has been
removed with the Dewow high pass filter.