Soil moisture is an essential parameter which strongly affects the biological, physical and geological processes within a soil and is key for the understanding of hydrological and carbon cycles. It is also critical for agricultural activities and water management and hence techniques for monitoring its state are important.
A wide variety of techniques exist for measuring soil moisture. Traditionally samples are taken from the ground and then weighed wet and dry to determine how much water is in the soil. This is far from ideal, is slow time consuming and disturbs the soil surface. Other in-situ sensors can be used to measure the dielectric permittivity of the soil from which moisture content can be inferred. Alternatively, remote sensing can be used to infer information about soil moisture using sensors on board satellites and aircraft. All techniques have their advantages and disadvantages with some better at local measurements and others better at obtaining wide area coverage.
Our colleagues Adam and Maxine from the technical support team and the staff from Starlab carrying out fieldwork in Lleida, Spain.
GNSSProbe is a new ESA funded study which looks at the potential of satellite navigation signals, commonly referred to as GNSS signals, such as those from GPS satellites, to estimate soil water content and to provide a cheap alternative to existing techniques.
GNSSProbe relies on the fact that GNSS signals have the ability to penetrate into soil. The signal is attenuated by the soil, and in particular by the water held within the soil. Hence by comparing the signal measured on the surface with the signal measured at a depth in the soil, it should be possible to calculate the soil moisture.
The work is funded by the European Space Agency (ESA) and led by Starlab Ltd.