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Agricultural Drainage Pipe Detection
Summary:
Enhancing the efficiency of soil water removal, and in turn crop productivity,
on land already containing an agricultural subsurface drainage system, typically
involves installing new drain lines between the old ones. However, before this
approach can be attempted, the older drainage pipes need to be located. A
research investigation has found that ground penetrating radar (GPR) was
successful in locating on average 72% of the total amount of pipe present at
thirteen test plots in southwest, central, and northwest Ohio. This method was
successful in finding clay tile and corrugated plastic tubing drainage pipe down
to depths of around 1 meter (3 feet) within a variety of different soil
materials. Additional research has focused on determining the impact that
equipment parameters, site conditions, field operations, and computer processing
have on GPR drainage pipe detection. Results with respect to equipment
parameters indicate that choosing the proper antenna frequency is crucial, and
antennas with a center frequency of around 250 MHz seem to work best. Also,
data quality is similar over a substantial range of spatial sampling intervals
and multiple signal averaging. In regard to the site conditions, shallow
hydrology, soil texture, and drainage pipe orientation all influence the GPR
response. Likewise, field operations (spacing distance between measurement
lines and bidirectional vs. unidirectional surveys) along with the algorithms
used in the computer processing sequence are very important considerations. The
information obtained in this study can hopefully be used to develop guidelines
that will enhance the potential for success of using ground penetrating radar to
locate buried agricultural drainage pipe. |
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This schematic illustrates how ground penetrating radar equipment (GPR) is used
to locate buried agricultural drainage pipes. The principle of the GPR method
involves directing an electromagnetic radio energy (radar) pulse into the
subsurface, followed by measurement of the elapsed time taken by the signal as
it is travels downwards from the transmitting antenna, partially reflects off a
buried feature, and is eventually returned to the surface, where it is picked up
by a receiving antenna. |
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These figures depict some typical ground penetrating radar (GPR) results with regard to locating buried agricultural drainage pipe. Figure a and Figure b are GPR generated images of the soil profile. As shown in these profiles, the GPR response to different buried drainage pipe orientations range from upside-down U-shaped to distinct linear banded features. Figure c is a map depicting the relative radar energy reflected back to the surface from a depth interval of 0.9 to 1.4 meters. Lighter shades on the map indicate greater reflected radar energy. Lightly shaded or white linear features often represent drainage pipes. Figure d is an interpreted map based on the GPR data showing the drainage pipe system with dashed lines. The blue line on Figure d indicates the line position along which the Figure a profile GPR data were collected. The red line on Figure d indicates the line position along which the Figure b profile GPR data were collected. |
