Airborne Acoustic Method to Determine the Volumetric Water Content of Unsaturated Sands

Mohamed, Mostafa; Horoshenkov, Kirill V.

doi:10.1061/(asce)gt.1943-5606.0000168

Cited by 5 publications

(5 citation statements)

References 32 publications

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“…The corresponding degree of saturations at different suction heads were then determined. The testing procedure and measurements are thoroughly explained in Mohamed and Horoshenkov (2009) and Sharma and Mohamed (2003).…”

Section: Experimental Approachmentioning

confidence: 99%

Effects of coolant flow rate, groundwater table fluctuations and infiltration of rainwater on the efficiency of heat recovery from near surface soil layers

et al. 2015

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Section: Experimental Approachmentioning

confidence: 99%

Effects of coolant flow rate, groundwater table fluctuations and infiltration of rainwater on the efficiency of heat recovery from near surface soil layers

et al. 2015

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“…A number of studies have focused on the characterization of the speed and absorption of sound in different types of soils [7,8] and a few attempts to characterize sound propagation through the soil with different moisture contents [9,10], but these are in-situ rather than non-intrusive remote sensing or proximal sensing methodologies.…”

Section: Introductionmentioning

confidence: 99%

“…A laboratory study [9,10] indicated that reflectance measurements can potentially give estimates of volumetric water content to  2%. A field measurement [16] where the moisture content was measured and varied used an acoustic impulse, with the amplitude of reflected sound doubling when the moisture content of grassland was changed from 10% to 35%.…”

Section: Introductionmentioning

confidence: 99%

Irrigation Control Through Acoustic Proximal Sensing of the Onset of Surface Water

Bradley¹,

Radionova²,

Ghimire³

et al. 2020

Preprint

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Irrigation is a useful crop enhancement procedure up to the point where free surface water appears. Thereafter, water can begin to flow into waterways, leaching nutrients and giving rise to environmental damage, as well as being a waste of a precious resource. The current work addresses the problem of measuring free water on the surface of agricultural soils by a real-time acoustic remote sensing method. Directional acoustic transmitter and receiver arrays are used to define a ‘footprint’ on the ground from which changes in reflectance are sensed. These arrays are mounted on a moving irrigator. Chirp signals are used to provide along-path resolution and to ensure robustness against unwanted acoustic background noise from farm machinery and the irrigator. Field measurements have been conducted above a well-defined ‘quadrat’ with controlled and measured water content, and also with the instrument mounted on an operational irrigator. A structured light camera mounted above the footprint is used to validate surface water fraction. It is found that the areal fraction of free water on the soil surface can be reliably estimated from changes in the amplitude of the reflected sound waves. The mechanism giving rise to the observed acoustic reflectivity changes is discussed and a model is developed which agrees with normalized intensity observations with a coefficient of determination R2 between 0.65 and 0.83. The rms error between model predictions and observations is comparable to the rms variation of the measurements, indicating that there is insignificant error due to the choice of model.

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“…A number of studies have focused on the characterization of the speed and absorption of sound in different types of soils [10,11] and a few attempts to characterize sound propagation through the soil with different moisture contents [12,13], but these are in-situ rather than nonintrusive remote sensing or proximal sensing methodologies. One potential method of sensing the nature of the soil surface is to use acoustic reflection.…”

Section: Introductionmentioning

confidence: 99%

“…The acoustic impedance is expected to have a clear increasing trend with a greater moisture content, which will plateau for saturated soil [10], [18,19]. A laboratory study [12,13] indicated that reflectance measurements can potentially give estimates of volumetric water content to ±2%. A field measurement [19], where the moisture content was measured and varied, used an acoustic impulse, with the amplitude of reflected sound doubling when the moisture content of grassland was changed from 10% to 35%.…”

Section: Introductionmentioning

confidence: 99%

Irrigation Control through Acoustic Proximal Sensing of the Onset of Surface Water

et al. 2020

View full text Add to dashboard Cite

Irrigation is a useful crop enhancement procedure up to the point where free surface water appears. However, over-irrigation can lead to an accumulation of free water on the soil surface, which in turn results in overland flow and a high risk of contaminant loss. The current work addresses the problem of measuring free water on the surface of agricultural soils by a real-time acoustic remote sensing method. Directional acoustic transmitter and receiver arrays are used to define a “footprint” on the ground from which changes in reflectance are sensed. These arrays are mounted on a moving irrigator. Chirp signals are used to provide along-path resolution and to ensure robustness against unwanted acoustic background noise from farm machinery and the irrigator. Field measurements have been conducted above a well-defined “quadrat” with controlled and measured water content and also with the instrument mounted on an operational irrigator. A structured light camera mounted above the footprint is used to validate surface water fraction. It is found that the areal fraction of free water on the soil surface can be reliably estimated from changes in the amplitude of the reflected sound waves. The mechanism giving rise to the observed acoustic reflectivity changes is discussed and a model is developed which agrees with normalized intensity observations with a coefficient of determination R2 between 0.65 and 0.83. The rms error between model predictions and observations is comparable to the rms variation of the measurements, indicating that there is insignificant error due to the choice of model.

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Airborne Acoustic Method to Determine the Volumetric Water Content of Unsaturated Sands

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Cited by 5 publications

References 32 publications

Effects of coolant flow rate, groundwater table fluctuations and infiltration of rainwater on the efficiency of heat recovery from near surface soil layers

Effects of coolant flow rate, groundwater table fluctuations and infiltration of rainwater on the efficiency of heat recovery from near surface soil layers

Irrigation Control Through Acoustic Proximal Sensing of the Onset of Surface Water

Irrigation Control through Acoustic Proximal Sensing of the Onset of Surface Water

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