Han Chunming

A novel method to reduce speckle in SAR images

A novel three-step method to reduce speckle in Synthetic Aperture Radar (SAR) images is presented. First, an edge detector is used to detect the edge orientations in SAR images. Second, using a data processing method named empirical mode decomposition, the SAR image is smoothed along four directions: horizontal, vertical, left diagonal and right diagonal, respectively. Third, the SAR image is reconstructed such that if the edge direction is horizontal, the pixel smoothed along the horizontal direction is used to reconstruct the image, and so on; if an edge is not detected, the mean of the four directionally smoothed images is used to reconstruct the image. Application of this method to SAR images has shown that it is well balanced in the quality of visual appearance, mean preservation, edge preservation, and reduction of the standard deviation.

A SAR interferogram filter based on the empirical mode decomposition method

In order to obtain a more accurate topographic model, a noise filtering step must be performed before the unwrapping of phase. In this article, a filter for suppressing speckle in SAR interferogram is proposed. The filter is based on the empirical mode decomposition (EMD) method which can separate the information to parts with different scale, when the parts related to the speckle is subtracted from the original interferogram, the speckle noise is reduced. The result is compared to that of two other methods and shows that EMD method is powerful to interferogram speckle noise reduction, as well as it can preserve fine details in the interferogram that are directly related to the ground topography and maintain phase values distribution.

A new multiscale edge detection technique [for synthetic aperture radar images]

An effective algorithm using the multiscale technique for detecting edges in synthetic aperture radar (SAR) images is presented utilizing the empirical mode decomposition (EMD). Since EMD is a one-dimensional data processing method, EMD is employed to image in two directions: horizontally (0/spl deg/) and vertically (90/spl deg/) to obtain two directionally smoothed images at different scales. In this way, different scales of image data were obtained. In order to obtain edge points of single pixel width, the grad of different image scales is computed. The edge map is extracted from different image scales based on a uniform space condition. Application of this method to SAR images has shown that the effectiveness of the method is quite satisfactory.

A method to segment SAR images based on histogram

The image segmentation is fundamental for many tasks of image processing and classification. Many methods for image segmentation have been developed. The some early segmentation methods are based on histogram, and some methods use local statistics, such as the mean, the standard deviation. Other methods are a combination of edge detection and region growing. It is difficult to determine the interval of the pixel value of a kind of ground object for the methods based on histogram in SAR image segmentation. In this paper, we proposed a method, which is based on histogram, and is similar to methods based on local statistics and region growing to segment the SAR images. Since speckle in SAR images disturbs the process of segmentation, we use an edge-preserving filter to reduce speckle. After the histogram is plotted, it will be noted that it is difficult to determine the interval of the pixel value of a kind of ground object. To determine the different ground object, for a pixel in a window of (2n+1)*(2n+1), the mean of all pixels in the window is M, if absolute value of a pixel value minus M is little T, then let the pixel value equal to M. T is a threshold selected based on the standard deviation and the classes of ground object. After the above process, it will be noted that it is still difficult to determine the interval of the pixel value of a kind of ground object in histogram. We use a data processing method named empirical mode decomposition to process the histogram. The pixel value interval of each ground objects can be determined. Based on the interval of each ground objects, we can segment the image. Application this method to SAR images has shown that the method can effectively segment the SAR images.

Re–Os Isotopic Age of the Hongqiling Cu-Ni Sulfide Deposit in Jilin Province,NE China and its Geological Significance

The major Hongqiling Cu-Ni sulfide deposit in central Jilin Province is located in the eastern part of the Central Asian Orogenic Belt. Rhenium and osmium isotopes in sulfide minerals from the deposit have been used to determine the timing of mineralization and the source of osmium and, by inference, the ore metals. Sulfide ore samples have osmium and rhenium concentrations of 0.28-1.07ppb and 2.39-13.17ppb, respectively. Ten sulfide analyses yield an isochron age of 223 ± 9 Ma, indicating that the Cu-Ni sulfide mineralization formed in the Early Triassic. The initial 187Os/188Os ratio is 0.295 ± 0.019 (MSWD = 1.14). This data indicates that the mineralization was derived mainly from a mantle source with some quantities of crustal components introduced into the rockforming and ore-forming systems during mineralization and magmatic emplacement. Together with the widespread occurrence of late Carboniferous-Permian mafic–ultramafic complexes and associated Permian Cu-Ni deposits in the western part of the Central Asian Orogenic Belt (Northern Xinjiang), we conclude that mantle-crustal interactions were active during the accretion-collisional processes that led to the Cu-Ni mineralization and considerable continental growth in the late Carboniferous-Permian to mid-Triassic.

Study on complex dielectric properties of saline soils

Using the Vector Microwave Network Analyzer in broad band (from 0.2 to 18 GHz), a controlled laboratory experiment was conducted on artificially prepared wet saline soil samples. The complex dielectric constants of soil samples in a wide range of moisture and salinity contents were measured and the relationship to the moisture and salinity of the soils were analyzed. The experiment results shows that the imaginary part of the dielectric constant of wet soil is more sensitive to the salinity of soils at low frequency range (f<5 GHz). It indicates that L band or P band SAR can be more effective in soil salinity detection. Secondly, 41 soil samples were collected along a profile from a dried salt lake in late April of 2001. Their moisture and salinity vary along the profile differently. The Vector Microwave Network Analyzer measured the complex dielectric constants of the collected soil samples in laboratory. C band, HH polarization RADARSAT data were simultaneously acquired on April 23, 2001. The backscatter intensity taken from RADARSAT image correlates with the complex dielectric constant. The correlation coefficient between the backscatter intensity and the real part of the complex dielectric constant is 0.23, and the imagine part of the complex dielectric constant is 0.66. This result shows that SAR will contribute to salinity monitoring program.

An Open Source Software and Web-GIS Based Platform for Airborne SAR Remote Sensing Data Management, Distribution and Sharing

With more and more Earth observation data available to the community, how to manage and sharing these valuable remote sensing datasets is becoming an urgent issue to be solved. The web based Geographical Information Systems (GIS) technology provides a convenient way for the users in different locations to share and make use of the same dataset. In order to efficiently use the airborne Synthetic Aperture Radar (SAR) remote sensing data acquired in the Airborne Remote Sensing Center of the Institute of Remote Sensing and Digital Earth (RADI), Chinese Academy of Sciences (CAS), a Web-GIS based platform for airborne SAR data management, distribution and sharing was designed and developed. The major features of the system include map based navigation search interface, full resolution imagery shown overlaid the map, and all the software adopted in the platform are Open Source Software (OSS). The functions of the platform include browsing the imagery on the map navigation based interface, ordering and downloading data online, image dataset and user management, etc. At present, the system is under testing in RADI and will come to regular operation soon.

Calibration and Validation of Airborne InSAR Geometric Model

The image registration or geo-coding is a very important step for many applications of airborne interferometric Synthetic Aperture Radar (InSAR), especially for those involving Digital Surface Model (DSM) generation, which requires an accurate knowledge of the geometry of the InSAR system. While the trajectory and attitude instabilities of the aircraft introduce severe distortions in three dimensional (3-D) geometric model. The 3-D geometrical model of an airborne SAR image depends on the SAR processor itself. Working at squinted model, i.e., with an offset angle (squint angle) of the radar beam from broadside direction, the aircraft motion instabilities may produce distortions in airborne InSAR geometric relationship, which, if not properly being compensated for during SAR imaging, may damage the image registration. The determination of locations of the SAR image depends on the irradiated topography and the exact knowledge of all signal delays: range delay and chirp delay (being adjusted by the radar operator) and internal delays which are unknown a priori. Hence, in order to obtain reliable results, these parameters must be properly calibrated. An Airborne InSAR mapping system has been developed by the Institute of Remote Sensing and Digital Earth (RADI), Chinese Academy of Sciences (CAS) to acquire three-dimensional geo-spatial data with high resolution and accuracy. To test the performance of the InSAR system, the Validation/Calibration (Val/Cal) campaign has carried out in Sichun province, south-west China, whose results will be reported in this paper.

Semi-physical Simulation of the Airborne InSAR based on Rigorous Geometric Model and Real Navigation Data

Raw signal simulation is a useful tool for the system design, mission planning, processing algorithm testing, and inversion algorithm design of Synthetic Aperture Radar (SAR). Due to the wide and high frequent variation of aircrafts trajectory and attitude, and the low accuracy of the Position and Orientation System (POS)s recording data, its difficult to quantitatively study the sensitivity of the key parameters, i.e., the baseline length and inclination, absolute phase and the orientation of the antennas etc., of the airborne Interferometric SAR (InSAR) system, resulting in challenges for its applications. Furthermore, the imprecise estimation of the installation offset between the Global Positioning System (GPS), Inertial Measurement Unit (IMU) and the InSAR antennas compounds the issue. An airborne interferometric SAR (InSAR) simulation based on the rigorous geometric model and real navigation data is proposed in this paper, providing a way for quantitatively studying the key parameters and for evaluating the effect from the parameters on the applications of airborne InSAR, as photogrammetric mapping, high-resolution Digital Elevation Model (DEM) generation, and surface deformation by Differential InSAR technology, etc. The simulation can also provide reference for the optimal design of the InSAR system and the improvement of InSAR data processing technologies such as motion compensation, imaging, image co-registration, and application parameter retrieval, etc.

The Paleoproterozoic Chibaisong Mafic-Ultramafic Intrusion and Cu-Ni Deposit, North China Craton: SHRIMP Zircon U-Pband Re-Os Geochronology and Geodynamic Implications

The Chibaisong magmatic Ni–Cu sulfide deposit (Jilin Province, NE China) is located in the Jiao-Liao-Ji Belt of the North China Craton. The ore-bearing mafic-ultramafic intrusions intrude the metamorphic rocks of the lowermost Sidaolazi Formation of the Anshan Group. SHRIMP zircon U-Pb dating gives a maximum depositional age of 2188 ± 8 Ma (95% confidence level, MSWD=3.2, n=8) for the host sedimentary rocks of the Chibaisong deposits. Rhenium and osmium isotopic analyses of Ni-and Cu-bearing sulfide minerals from the deposit have been used to determine the timing of mineralization, the source of osmium, and, by inference, the source of ore metals. Sulfide ore samples have Os and Re concentrations ranging from 19 to 490 ppb and from 0.47 to 13.97ppb, respectively. Analyses of these data yield a six-point isochron age of 1885 ± 94 Ma. An initial 187Os/188Os ratio of 0.80 ± 0.16 (mean square of weighted deviates=0.17) and δ34S values of -1.1 to +0.7‰ for the ores, as well as initial 87Sr/86Sr ratios of 0.703-0.708 for metalliferous intrusions, suggest a magmatic source for the ores, with the melts dominated by mantle contributions. The Chibaisong intrusion was previously considered to have formed under a post-orogenic extensional setting in the Early Cretaceous. However, our new Re-Os geochronological result indicates that the Chibaisong mafic-ultramafic intrusion, along with the Cu-Ni deposit, was related to a Paleoproterozoic extensional event, not resulting from an Early Cretaceous post-orogenic extension as previously considered.