Ground-based synthetic aperture radar (GBSAR) is a powerful tool used in monitoring structures such as bridges and dams. However, despite the extremely short range of GBSAR interferometry, the atmospheric effects cannot be neglected. The permanent scatterer (PS) technique is an effective operational tool that utilizes a long series of SAR data and detects information with high accuracy. An algorithm based on the PS technique is developed in accordance with the phase model used in GBSAR interferometry. Atmospheric correction is carried out on a real campaign (Geheyan Dam, China). The atmospheric effects created using this method, which utilizes SAR data, can be effectively reduced compared to when plumb line data are used.
Precise topographical information has a very important role in geology, hydrology, natural resources survey and deformation monitoring. The extracting DEM technology based on synthetic aperture radar interferometry (InSAR) obtains the three-dimensional elevation of the target area through the phase information of the radar image data. The technology has large-scale, high-precision, all-weather features. By changing track in the location of the ground radar system up and down, it can form spatial baseline. Then we can achieve the DEM of the target area by acquiring image data from different angles. Three-dimensional laser scanning technology can quickly, efficiently and accurately obtain DEM of target area, which can verify the accuracy of DEM extracted by GBInSAR. But research on GBInSAR in extracting DEM of the target area is a little. For lack of theory and lower accuracy problems in extracting DEM based on GBInSAR now, this article conducted research and analysis on its principle deeply. The article extracted the DEM of the target area, combined with GBInSAR data. Then it compared the DEM obtained by GBInSAR with the DEM obtained by three-dimensional laser scan data and made statistical analysis and normal distribution test. The results showed the DEM obtained by GBInSAR was broadly consistent with the DEM obtained by three-dimensional laser scanning. And its accuracy is high. The difference of both DEM approximately obeys normal distribution. It indicated that extracting the DEM of target area based on GBInSAR is feasible and provided the foundation for the promotion and application of GBInSAR.
Ground-Based Synthetic Aperture Radar interferometry (GBInSAR) has generated movement with sub-millimeter accuracy in line-of-sight(LOS) direction, and it can provide movement images with high spatial and temporal resolution. Though the fluctuation of atmospheric environment affects interferometric phases strongly, GBInSAR can be used for deformation measurement after removing the interference phase and transforming the displacement from LOS direction to radial and tangential. This paper provides a comparison of different atmospheric disturbance correction techniques. We made an experiment of deformation measurement about Geheyan Dam on Qingjiang to estimate the movement caused by atmosphere. In the experiment, displacement information of the dam was obtained by IBIS-L system and atmospheric parameters (humidity, temperature and barometric pressure) were collected from the weather station located on the dam. The collection process lasted for several days. By processing and analysis the data of a whole day without equipment malfunction, the results show an atmospheric delay of 15mm when the system located 1000m away from the target dam and atmospheric correction should be reinforced somehow for most Ground-Based InSAR applications. Then three correction algorithms are presented in order to weaken the influence from atmospheric disturbance. The techniques respectively based on the atmospheric parameters, Ground Control Points(GCP) and distribution model are quantitively compared using a reference dataset gotten by inverted perpendicular lines. And the accuracy of each method are finally drawn. It could be seen that the atmospheric disturbance be weaken by the three methods with reliable results and error of the technique based on distribution model was less than 2mm with the highest reliability. This analysis is followed by a discussion of the advantages and the limitations of each technique.
Only the displacement along the radar line of sight can be got in Ground Based Synthetic Aperture Radar (GBSAR). In order to extract high-precision three-dimensional displacement field of research area, in this article, we research deeply the method which integrates both three-dimensional laser scanning and GBSAR techniques. It is proved that high precision three-dimensional displacement field information can be extracted with this method through analyzing case and assessing the accuracy of three-dimensional displacement field. The method has a good practical value.
The subsidence was monitored by micro‐deformation monitoring system IBIS based on ground‐based SAR interferometry technology. The displacement in the line of sight can be corrected along the subsidence direction after atmospheric disturbances reduction, then get continuous deformation map of observation area in 24 hours. These experiments show that the Ground‐Based InSAR technology can be applied to subsidence monitoring with millimeter precision, and IBIS system have an advantage in dynamic monitoring of micro‐deformation.