We evaluated the potential of a digital ground‐penetrating radar (GPR) for soil moisture determination. Ground‐penetrating radar offers a fast and nondestructive way for estimating the soil dielectric constant and may be an interesting tool for low‐cost mapping of soil moisture. Two modes of operation were considered: (i) the ground mode where signal propagation between the antennas placed on the surface was studied; (ii) the airborne mode where the antennas are raised 5–15 m above the soil surface. Variables describing the GPR response were defined and related to the soil moisture. It is shown from field experiments that the GPR measurements performed at 200 MHz in both modes are mainly affected by the moisture in the 10‐ to 20‐cm topsoil layer. In the ground mode, the obtained soil moisture error after calibration was lower than 0.03 m3/m3. In the airborne mode, soil moisture estimations were less accurate (0.046 m3/m3). The wave spreading loss characterization has to be improved to get an altitude‐independent GPR measurement.
Shrimp culture is a sector of aquaculture that has a high potential for poverty alleviation and rural development in Vietnam. However, the development of this activity induces changes that potentially have negative impacts on the environment, one of which is wetland deterioration. This paper describes the use of a proposed change detection methodology in the assessment of mangrove forest alterations caused by aquaculture development, as well as the effectiveness of the measures taken to mitigate deforestation in the district of Giao Thuy, Vietnam, between 1986Vietnam, between , 1992Vietnam, between and 2001. Geometric and radiometric corrections were applied to Landsat images prior to identifying changes through comparison of unsupervised classifications. Changes were afterwards validated using a thresholding method based on Tasselled Cap feature image differencing and a rule-based feature selection matrix. The matrix is used to identify the feature that is most efficient at detecting the presence of change between given land-cover classes. The proposed approach aims to minimize commission errors in the postclassification change detection process. The results suggest that 63% of mangrove areas apparent in 1986 had been replaced by shrimp ponds in 2001. Between 1986 and 1992, 440 ha of adult mangrove trees had disappeared, whereas the mangrove extent increased by 441 ha between 1992 and 2001. This recovery is attributed to reforestation projects and conservation efforts that promoted natural regeneration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.