Soil Water Content Estimation Using High-Frequency Ground Penetrating Radar

Abstract

The rapid high-precision and nondestructive determination of shallow soil water content (SWC) is of vital importance to precision agriculture and water resource management. However, the low-frequency ground penetrating radar (GPR) technology currently in use is insufficient for precisely determining the shallow SWC. Therefore, it is essential to develop and use a high-precision detection technology to determine SWC. In this paper, a laboratory study was conducted to evaluate the use of a high-frequency GPR antenna to determine the SWC of loamy sand, clay, and silty loam. We collected soil samples (0–20 cm) of six soil types of loamy sand, clay, and silty loam and used a high-frequency (2-GHz) GPR antenna to determine the SWC. In addition, we obtained GPR data and images as well as characteristic parameters of the electromagnetic spectrum and analyzed the quantitative relationship with SWC. The GPR reflection two-way travel times and the known depths of reflectors were used to calculate the average soil dielectric permittivities above the reflectors and establish a spatial relationship between the soil dielectric permittivity ( ε ) and SWC ( θ ), which was used to estimate the depth-averaged SWC. The results show that the SWC, which affects the attenuation of wave energy and the wave velocity of the GPR signal, is a dominant factor affecting the soil dielectric permittivity. In addition, the conductivity, magnetic soil, soil texture, soil organic matter, and soil temperature have substantial effects on the soil dielectric permittivity, which consequentially affects the prediction of SWC. The correlation coefficients R2 of the “ θ ~ ε ” cubic curve models, which were used to fit the relationships between the soil dielectric permittivity ( ε ) and SWC ( θ ), were greater than 0.89, and the root-mean-square errors were less than 2.9%, which demonstrate that high-frequency GPR technology can be applied to determine shallow SWC under variable hydrological conditions.

CSRR-Based Microwave Sensor for Dielectric Materials Characterization Applied to Soil Water Content Determination

“…For the quartz sand soil samples, measurements were made up to a concentration of 10% due to the fact that, with the concentration of 15% of water for the amount of material in the sensor, free water, i.e., not absorbed by the soil sample, drastically influenced the result obtained. The values measured for the red clay presented low relative permittivity values due to the absorption characteristic and high conductivity of this type of soil, thus causing higher dielectric losses [29].…”

“…Some of them include, for example, monitoring of landslide and agricultural risk zones. Thus, several authors have proposed practical and simple ways to perform this type of characterization, such as a sensor that extracts moisture from soil samples based on Kopecky cylinders [28] or using high-frequency radar penetration [29]. The amount of water in the soil can be verified by measuring the relative permittivity of the sample [30], since the relative permittivity of the water is tens of times greater than the permittivity of the soil, with values of 80 for water and between 2 and 3 for dry sand.…”

Real-Time Pattern-Recognition of GPR Images with YOLO v3 Implemented by Tensorflow

“…Most of them appear as parabolic with openings downward or obvious energy reflection in electromagnetic waves format. GPR moves along the survey line and continuously collects a series of trajectories (A-scan) to form electromagnetic wave B-scan images [ 24 ]. Before YOLO v3 training, GPR images were collected in this way.…”

Effect of Shallow-Buried High-Intensity Mining on Soil Water Content in Ningtiaota Minefield

“…The GPR method has been widely popular with many scholars because it can realize continuous, rapid and large-scale SWC detection [36][37][38][39][40]. The GPR method has great advantages in the detection of SWC in large-area mining areas.…”