Changbao Zhou

An improved CFAR model for ship detection in SAR imagery

This paper presents an improved constant false alarm rate (CFAR) model for ship detection in synthetic aperture radar (SAR) imagery. The model includes the probabilistic neural networks, CFAR technique, golden section method and area growth method. It is compared with other ship detection methods. The results show that the improved CFAR model performs well

Nonlinear internal wave amplitude remote sensing from SAR imagery

The amplitude of internal waves is very difficult to retrieve from satellite. In this paper, a method is given to estimate the amplitude of nonlinear internal waves from synthetic aperture radar (SAR) imagery. It is assumed that the observed groups of nonlinear internal wave packets on SAR imagery are generated by local semidiurnal tides. The mean distance between the leading crest of two successive wave packets has been used to derive the group velocity of the nonlinear internal waves. The amplitude of nonlinear internal waves has been calculated from a model which consists of the KdV equation, action balance equation and Bragg scattering model. Case studies in China Seas show reasonable results.

Fractal characterization of Ikonos imagery

An IKONOS image was used to examine the spatial complexity of the band spectra of remote sensing. Triangular prism method and double blanket method were applied to calculate the fractal dimensions of all bands for each land cover type. The results show the image texture characteristics of the images by bands and land cover types. As the conclusions, the fractal dimensions of all bands of each land type range between 2.0 and 3.0. But different type sub-images show different complexities, thus different dimensions. Dimension values reflect spectral characters and spatial characters of sub-images. Thus, it is believed that the measurement and analysis of land cover can be more effectively and efficiently realized using fractal characterization of high spatial and spectral resolution remote sensing data.

Shallow water bathymetric surveys by spaceborne synthetic aperture radar

A numerical model for shallow water bathymetric surveys by spaceborne synthetic aperture radar (SAR) and its calculation procedure have been developed based on the SAR imaging mechanism of sea bottom topography. Water depths of the Xiaoyinsha sandwave off the east coast of Jingsu province have been calculated from the ERS-1 SAR imagery. The results have been compared with the sea chart. It is shown that the agreement between the image-calculated bathymetric pattern and that in the chart is excellent. A root mean square difference accuracy of 0.42 m has been achieved.

The dynamic monitoring and infinite-scale management of coastal zone with remote sensing and fractal approach

The new needs for quantitative and precise detection for coastline dynamic changes and their environmental factors are addressed with the fast and more developing activities of coast areas. The magnitudes from satellite or airborne remote sensing and in-situ observed data, and different scale mapping as well as multi-dimension changes are increasingly important. So the problems on capture, store, process, display and management of an unprecedented amount of information have become a very important. Satellite remote sensing associated with fractal approaches presented here are new methodologies to solve related scientific problems. The situation and requirement of coast zone are briefly introduced in the paper at the first. The theories and models of fractal system and the examples of their application in coastline and the possibility of infinite scale managements of the coastline are described in detail. The potential of satellite remote sensing associated with fractal approach in detecting and manage of coast zone is discussed and concluded at the final of the paper.

The dynamic monitoring and management of coastal zone with SAR remote sensing and fractal approach

It is known that coastal zone and its environments are the complex and specialized areas. Synthetic aperture radar (SAR) with all weather is the powerful tools for monitoring the dynamic changes of those regions, and fractal approaches may be a good ideal technologies for managements on the unprecedented amount of information from the coastal spatial and temporal processes and remote sensing images etc. database. The needs of coastal dynamic monitoring are introduced at the first. The imaging mechanisms and the technologies as well as the example studies of SAR detecting coastal zone are described in detail.

Ship detection in presence of sea clutter from temporal sequences of navigation radar images

This work presents a method to suppress the sea clutter for radar images acquired from ordinary navigation radar sensors, which are incoherent radars working in X-band and horizontal polarization. The proposed method considers short temporal sequences of consecutive navigation radar images. This method, which is based on rotation-to-rotation correlation and the variation of sea clutter response with range, can be described as follows. 1) To cumulate the k (k>1) temporally consecutive images. 2) To fit the variation of the sea clutter intensity with range for every scan line of the cumulative image and to subtract the fitted sea clutter intensity from the cumulative image for every pixel. 3) To calculate the threshold value of detection by applying the Constant False Alarm (CFAR) model and the Probabilistic Neural Networks (PNN) model. 4) To threshold the resulting image with the obtained threshold. 5) To remove the false alarm by utilizing the flood fill algorithm to determine the connected area size of any probable target in the binary image. Temporal sequences of navigation radar images were used to test the performance of the proposed method. The results obtained show that the proposed method is able to reduce significantly the sea clutter from the radar images and detect efficiently a ship embedded in the sea clutter. The detection precision is provided according to the experimental results.

Detection studies of the ship targets on sea-surface based on fusion of multi-parameter satellite SAR images

Recently, the developments of multi-parameter SAR systems are so fast. Those images are of multi-bands, multi-polarizations, multi-look-angles, multi-resolutions and multi-swaths and so on respectively in order to meet the different needs from ocean, atmosphere and land users. The safeties and operations for the ships over sea surface offer important supports based on real detection from satellite SAR. So, Satellite SAR remote sensing methodology is of great potential for monitoring ships. The research areas of the paper include satellite SAR developing states and its progresses, SAR imaging mechanisms and studied techniques for ship detection, example research and compare their results by the approach and tradition. The studies indicate that the monitoring technology for ship provided by the studies is of important application values and develop potential.

Ocean surface wind, wind stress, and drag coefficient remote sensing by SAR

Wind wind stress and drag coefficient of ocean surface are very important parameters in the studies of ocean and atmospheric dynamics especially in that of air-sea interaction. It is shown in this paper that wind wind stress and drag coefficient of ocean surface can be measured remotely with high resolution by synthetic aperture radar (SAR). A model has been developed based on SAR imaging mechanisms of ocean surface capillary waves and short gravity waves. A Radarsat SAR image of coastal ocean of south of Hainan Island has been used to calculate wind stress and drag coefficient. Good results have been achieved.

Simulation of the Chinese airborne SAR image spectrum

The image spectrum ofthe Chinese airborne synthetic aperture radar (SAR) has been simulated using a simulation model based on the closed nonlinear integral transformation. The results of the simulation have been used to study the ocean wave imaging mechanism. The ability of the Chinese airborne SAR to observe ocean waves in the China Seas is discussed.