Soil Moisture Content Estimation Using Active Infrared Thermography Technique: An Exploratory Laboratory Study

Abstract

Small scale laboratory testing was conducted to estimate the water content of sandy soils using a non-destructive and non-contact infrared thermography (IRT) technique. Tests were carried out under active conditions, with a constant halogen lamp light (400W). In this study, the aim was to explore the feasibility of using IRT to assess the water content of sandy soil. The laboratory tests were conducted in three stages: the first stage involved characterizing the soil, the second stage involved using the gravimetric oven-drying method to measure the soil’s water content (to act as a measurement reference), and the final stage involved estimating the soil’s water content using the IRT technique. Soil samples were prepared with five different water content percentages. The samples were then photographed with an ICI IR-Pad 640 P Series camera, which had an image resolution of 640 x 480 pixels and a capture rate of 6 frames/ minute. The emissivity correction used was 0.98. The soil surface temperature was captured in both the heating and the cooling phase, with the temperature taken from a specific thermal image area called the Region of Interest (ROI). Water content measurements were taken for each sample using the oven-drying method at the initial stage, and at the end of the heating and cooling phases. The procedure produced a good result in the heating phase. The soil moisture contents and surface temperatures were inversely related and formed a linear line with a high degree of accuracy (r²= 0.9138). The procedure was compared with the gravimetric oven-drying method at the end of the study. It is found that IRT successfully estimated soil water content.