Guo Huadong

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.

Use of multifrequency, multipolarization shuttle imaging radar for volcano mapping in the Kunlun Mountains of Western China

Abstract A group of volcanoes northeast of Aksayqin Lake, in the western Kunlun Mountains, China, have been identified on multifrequency, multipolarization spaceborne imaging radar-C/X-band synthetic aperture radar (SIR-C/X-SAR) images. Field observations made on the volcanic morphology and terrain features are described in this paper. Analysis of single-band, single-polarization radar backscatter coefficients (σ°) shows that LHV best discriminates the two types of lava flows (pahoehoe and aa lavas), alluvium, and bedrock. The factors affecting the radar backscatter coefficient also are analyzed. Finally, this paper presents KAr isotopic ages of volcanic samples collected in the field and discusses the volcanism in the area.

On paleodrainage evolution in mid-late Epipleistocene based on radar remote sensing in northeastern Ejin Banner,Inner Mongolia

Radar remote sensing can acquire information of sub-surface covered by sand in arid area, detect surface roughness and vegetation coronet’s layer and linear feature such as linear structure and channel sensitively. With sediment facies analysis, this paper studies the features of environmental evolution in mid-late Epipleistocene (60 ka BP-20 ka BP) in northeastern Ejin Banner. The conclusions are listed as follows: (1) The evolution of the three lakes, i.e. Gaxunnur, Sugunur and Tian’e lakes, are dominated by faults and regional climate. (2) By analyzing sedimentary section of old Juyanze Lake, the three lakes used to be a large outflow lake before 50 ka BP in northeastern Ejin Banner, and at 50 ka BP, temperature declined rapidly in northwestern China. The event caused the lake’s shrinkage. (3) By fault activity uplift in the northern part of old Juyan Lake and depression in the southern part, the lake’s water followed from north to south at around 35 ka BP, old Juyanze fluvial fan was formed. At the same time, Juyan Lake separated from Sugunur Lake and Wentugunr old channel was abandoned. (4) In recent 2000 years, Ruoshui River is a wandering river, sometimes it flows into Juyan Lake and sometimes Sugunur and Gaxunnur lakes. Due to human activities and over exploitation, the oasis ecosystem is rapidly degenerated in 15 years (1986–2000).

Extended Three-Stage Polarimetric SAR Interferometry Algorithm by Dual-Polarization Data

Until now, most polarimetric synthetic aperture radar interferometry (PolInSAR) research has been based on full-polarization (HH + HV + VH + VV) SAR data, which can provide complete polarimetric information but usually have a smaller swath and lower spatial resolution than dual-polarization (dual-pol) data. Some existing researches concern the dual-pol PolInSAR; however, these works did not perform the coherence optimization process which may make the inversion unstable. In this paper, the PolInSAR technique based on dual-pol (HH + HV) SAR data is investigated in order to demonstrate its validity for forest height retrieval and thus show that PolInSAR is better able to meet the requirements of global-scale research. We extend the three-stage inversion process and coherence optimization algorithm to dual-pol PolInSAR. In addition, based on the random volume over ground model, a search method for finding the volume-only coherence on ambiguous line segments is proposed. Finally, the dual-pol PolInSAR technique is applied to forest height estimation using airborne L-band SAR data acquired by the E-SAR system over the Traunstein test site in Germany. The forest heights estimated by dual-pol PolInSAR are compared with those estimated using the full-pol mode and also with measurements made in situ. The results show that dual-pol PolInSAR can obtain similar estimated forest heights to the full-pol mode and also that the search method for volume-only coherence retrieval can improve the inversion accuracy. The coefficient of determination (r2) for the relation between the dual-pol PolInSAR and the in situ measurements is 0.7287.Until now, most polarimetric synthetic aperture radar interferometry (PolInSAR) research has been based on full-polarization (HH + HV + VH + VV) SAR data, which can provide complete polarimetric information but usually have a smaller swath and lower spatial resolution than dual-polarization (dual-pol) data. Some existing researches concern the dual-pol PolInSAR; however, these works did not perform the coherence optimization process which may make the inversion unstable. In this paper, the PolInSAR technique based on dual-pol (HH + HV) SAR data is investigated in order to demonstrate its validity for forest height retrieval and thus show that PolInSAR is better able to meet the requirements of global-scale research. We extend the three-stage inversion process and coherence optimization algorithm to dual-pol PolInSAR. In addition, based on the random volume over ground model, a search method for finding the volume-only coherence on ambiguous line segments is proposed. Finally, the dual-pol PolInSAR technique is applied to forest height estimation using airborne L-band SAR data acquired by the E-SAR system over the Traunstein test site in Germany. The forest heights estimated by dual-pol PolInSAR are compared with those estimated using the full-pol mode and also with measurements made in situ. The results show that dual-pol PolInSAR can obtain similar estimated forest heights to the full-pol mode and also that the search method for volume-only coherence retrieval can improve the inversion accuracy. The coefficient of determination (r) for the relation between the dual-pol PolInSAR and the in situ measurements is 0.7287.

Edge preservation evaluation of digital speckle filters

This paper makes three contributions. It clarifies the definition of edge preservation in SAR images. The definition of edge preservation is important for edge preservation evaluation of digital speckle filters. Only if the definition of edge preservation is reasonable, can the edge preservation evaluation be successfully performed. Second, an algorithm to evaluate edge preservation of digital speckle filters is proposed. Third, we analyze the reason why the enhanced Lee, enhanced Frost, gamma, and Kuan filters cannot effectively preserve edges. The main contribution in this paper is that we clarified the difference between edge preservation and edge point preservation. It is important to develop new methods to reduce speckle in SAR images, which can successfully preserve edges in smoothed images.

Three Parallel Rivers of Yunnan Protected Areas

The Three Parallel Rivers of Yunnan Protected Areas is a nature reserve extending over 170,000 km2 within the undulating mountains of northwest Yunnan Province. It is the combination of seven geographical features over eight geographic regions. The natural landscape comprises three great rivers of East Asia, namely, the Jinsha River (the upper reaches of the Yangtze River), the Lancang River (the upper reaches of the Mekong River), and the Nujiang River (the upper reaches of the Salween River). The mountains lying between these rivers are parallel in a north to south direction with gorges as deep as 3 km and flankfed by two 6 km high glaciated peaks. The three river systems and three ranges of mountains yield a pattern of the Chinese character “Jll.” The Three Parallel Rivers of Yunnan Protected Areas is representative of landscapes demonstrating the Earths evolution over major geological time periods and bio-evolution at important phases. Its distinctive bio-diversity and isolated geography makes it an important habitat for rare and endangered species.

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.

Research on global change scientific satellites

Global change now poses a severe threat to the survival and development of mankind. Large-scale, real-time, highly accurate Earth observation from space has become a key technology used to observe global change. China is one of the most influential countries affecting and being affected by global change, yet it has no scientific satellite for global change research so far. Developing global change scientific satellites not only would meet an important demand of China, but also would be a valuable contribution to the world. By analyzing the mechanisms of space-based observation of variables sensitive to global change, this paper explores the concept of global change scientific satellites, and proposes a series of global change scientific satellites to establish a scientific observation system for global environmental change monitoring from space.

A new airborne Earth observing system and its applications

A new airborne Earth observing system has been developed in China directed by the Expert Group for Information Acquisition and Processing Technology, Hi-tech Research and Development Program of China during the period from 1996 to 2000. The system is composed of 5 remote sensing sensors, including a 128-band modular imaging spectrometer with high spectral resolution, 244-band hyperspectral imaging spectrometer, an area array CCD digital camera with high spatial resolution, a 3 D imager with real time imaging capability, and an L-band SAR with 3m resolution. These sensors are installed onto different aircraft according to their performance, therefore, forming a set of distributive airborne Earth observing system. Since 1998, demonstrative applications study using the system has been conducted, and remote sensing imagery over 10 test sites have been acquired. These data after processing and analysis have achieved very satisfactory application results in rice classification, urban planning, water pollution and desertification monitoring, natural hazards monitoring, mineral exploration and other fields. These demonstrate the roles and application potentials of the new airborne system for Earth observation.