Aiqing Shi

Comparison of ship detection algorithms in spaceborne SAR imagery

The algorithms discussed in this paper are three Constant False Alarm Rate (CFAR) models, which include the Probabilistic Neural Network(PNN) model, the K-Gamma model and the double parameters model. The SAR data utilized in the paper include ERS-2, ENVISAT and Radarsat SAR data. The data are applied in ship detection experiments and the results of ship detection of three models are compared. The results show that the PNN models applicability is the best .The performance of PNN model in ERS and ENVISAT SAR data is better than the K-Gamma model. The K-Gamma model can only do well in Radarsat SAR data. The double parameters model can fit local distribution of SAR image in the sea.

Raster to vector conversion of classified remote sensing image

An approach to vectorization of classified remote sensing image is presented based on the characteristics of raster data. This approach consists of three digitizing steps during the raster to vector convening: pre-processing, processing and postprocessing. First, all image pixels are categorized to some different types according to the characteristics of raster data. Then, polygons are generated by tracing these typed image pixels, with topological attribute built-in. Finally, the vector data are post-processed to reduce the redundancy and stored to GIS’s based file. Compared to traditional methods this approach creates topological information of vector data automatically during converting. It has high performance, and could be implemented step by step. The result vector data could be applied and used directly in the geographical information system. An example is used to illustrate this approach with classified Landsat TM image. Keywords-Raster to Vector Conversion; Topology; Remote Sensing Imag; Geographical Information System

Satellite observation of the Zhejiang-Fujian coastal front in the East China Sea

The Zhejiang-Fujian coastal front in the East China Sea has been studied using an 12-year time series (1991-2002) of Advanced Very High Resolution Radiometer (AVHRR) images. Satellite observation has shown that the front exits all year round and has a length scale of about 597 km. The strength and width of the front vary with average values of 0.14 degC/km and 14 km respectively. The front is characterized by the presence along its edges of rings which have a time scale of 1-7 days and a length of 30-90 km

AVHRR observations of the Yangtze River plume

The Yangtze River plume has been studied using NOAA AVHRR thermal infrared images. AVHRR observations have shown that the Yangtze River plume is a variable phenomenon. It varies daily, seasonally and annually. The thermal front of the Yangtze River plume has a length scale of about 371 km. The strength and width of the front vary with average values of 0.14°C/km and 16 km respectively. The temporal and spatial variations of the front have been discussed. KeywordsAVHRR;Yangtze River plume front; East China Sea.

Satellite Measurements of the Zhejiang-Fujian Coastal Front in the East China Sea with an Improved Front-Following Algorithm

The Zhejiang-Fujian coastal front is an important front in the East China Sea. The frontal parameters have been measured using an improved front-following algorithm with Advanced Very High Resolution Radiometer (AVHRR) data. The Frontal parameters including position width mean SST SST difference and gradient of the front have been retrieved.

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.

An improved front-following algorithm for oceanic front measurement with AVHRR SST imagery

An improved oceanic front measurement algorithm is developed based on Front-Following technique. Two approaches are introduced to improve the original Front-Following algorithm. First, an edge-detection operator is applied to the satellite image, giving initial algorithm parameters, such as the information on the position of the oceanic front. Second, instead of a size-fixed extraction window, the geographic window is used in the new algorithm while following an oceanic front. An example is used to illustrate the improvements using the new algorithm to measure coastal fronts in the East China Sea with AVHRR SST Imagery.

SAR imaging conditions of topography-induced current front in a tidal channel

The Lingding channel appears as a quasi-linear dark-bright feature in a TerraSARX synthetic aperture radar (SAR) image acquired in the area of Pearl River Estuary (PRE), China on October 25, 2010. The tidal current in this area is almost parallel to the major axis of the Lingding channel. In this paper, researches on the SAR remote sensing imaging conditions of channel topography have been carried out based on the analysis of SAR imaging mechanism. A 3-D simulation imaging model of SAR shallow water topography for the PRE consisting of a 3-D hydrodynamic model and a radar simulation model has been used. Simulations on SAR remote sensing imaging of channel topography have been carried out under different radar parameters and sea conditions, then the best conditions for SAR imaging of the PRE shallow water topography are given.

Chinese progress toward marine applications of synthetic aperture radar

This paper presents the progress toward marine applications of synthetic aperture radar (SAR) data and a review of the SAR satellite program in China. The technique development includes the development of algorithms and of methodology for extracting oceanographic parameters from SAR data. Marine applications range from environmental monitoring to oceanographic research. Two series of SAR satellites have been planned. The first SAR satellite of the Environmental and Disaster Monitoring Satellite series (HJ series) will be launched in 2009 while the first SAR satellite of the Ocean SAR Satellite series (HY-3 series) is in planning phase. A description is given of the instruments and their plateforms.

SAR measurements of the Taiwan Shoal in China

The submarine sand waves of the Taiwan Shoal in the coastal area of China have been observed with ERS-1 SAR images. A numerical model for shallow water bathymetric survey by SAR has been used to derive the heights and the slopes of the submarine sand waves while a feature tracking method has been applied to measure the movement of the submarine sand waves with sequential images. The results show that the submarine sand waves align parallel to the east direction with a height scale of 2-6m and a slope scale of 2°-14°. The lengths and widths of the submarine sand waves are about 500-5000m and 200 to 2000m respectively. The submarine sand waves move towards the south and the southeast. The displacement of the submarine sand waves varies between 20 to 450m with an average value of about 146m.