Comparison of the remote sensed soil moisture estimations and in-situ measurements

Soil moisture is an important parameter of the hydrological cycle used in many areas such as irrigation and water resources management. Remote sensingbased methods are very effective in determining the soil moisture of large areas. However, soil moisture estimates made by remote sensing differ from soil moisture values measured on site. Determining these differences will make it easier to establish a relationship between values estimated from remote sensing and values measured in situ. In this study, differences between soil moisture estimates made using remote sensing and soil moisture measured in situ were investigated. In this context, the soil moisture values at a depth of 20 cm measured at a total of 6 meteorological stations in Denizli and the surrounding area were compared with the soil moisture values estimated using the Oh 2002 model from the GRD images of the Sentinel-1 radar satellite. Firstly, the back reflection values (σvv, σvh) taken in satellite images and the measured soil moisture values were compared; in general, σvv showed a more successful result than σvh. It has been observed that there is generally a low correlation between measured soil moisture and soil moisture estimated by the Oh 2002 model. In order to increase the effectiveness of soil moisture estimates made by remote sensing, in-situ measurements must be reliable and taken at depths close to the surface. It was thought that measurements made in this way could help improve remote sensing models and create soil moisture maps.