Comparison between thermal airborne remote sensing, multi‐depth electrical resistivity profiling, and soil mapping: an example from Beauce (Loiret, France)

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ABSTRACTA wide variety of remote sensing and ground‐based (proximal sensing) methods have been developed to describe soil physical properties and their lateral variations. Remote sensing enables the estimation of soil properties over large areas, but the information is often limited to the soil surface. Ground‐based methods enable the derivation of soil properties for the whole soil column thickness, although these methods cannot be conducted over large areas. The aim of the present study is to contribute to the assessment of the efficacy of airborne thermal prospection over bare soils in soil mapping. This study focuses on a comparison between this technique, which can investigate over the whole soil column thickness after a sufficiently long transient heat exchange period, and pedo‐logical and electrical resistivity data that were recorded for three different depths of investigation.The study area is located in the Beauce region, where the soils (haplic Calcisol or calcaric Cambisol) consist of a loamy–clay layer that is 0.3 m–1.4 m thick and overlies Tertiary Beauce limestone. Thermal measurements were recorded by ARIES radiometer in December, after six days of heat loss from the ground. The investigation depth could thus be considered to be larger than the thickness of the ploughed layer. Comparisons using statistical analyses between the thermal measurements, electrical resistivity, and pedological data demonstrated that: (i) the spatial organization of the thermal inertia map is similar to the spatial organization of the 0‐m to 1.7‐m resistivity map; and (ii) the thermal apparent inertia values are significantly different between the haplic Calcisols and the calcaric Cambisols and can thus be mapped with a high spatial resolution over large areas. The applicability of thermal prospecting in soil mapping opens up many possibilities considering the present advances in light‐infrared radiometers. Beside agronomical concerns, this methodology will also facilitate progress in engineering applications, including the cross‐estimation of electrical and thermal properties.