This paper investigates the ERS Scatterometer soil moisture products precision over a half-degree region in Southwestern France. Based on a high resolution soil moisture simulation (1 km2) validated at the local scale, the ERS-scat product is assessed at its own resolution (about 50 ¿ 50 km2). The study points out the suitable quality of the surface soil moisture product (root mean square error equal to 0.06 m3.m-3 for a 4-year period) and assesses the retrieved root-zone soil moisture accuracy provided by a semi-empirical methodology exclusively based on surface soil moisture products.