Xiuwan Chen

Object-oriented classification and application in land use classification using SPOT-5 PAN imagery

High-resolution remotely sensed data have been actively employed in urban land use/cover. Object-oriented classification techniques based on image segmentation are being actively studied in the high-resolution image process and interpretation to extract a variety of thematic information. Different from the pixel-based image analysis, the processing of the object-oriented method is based on image object or segment, not single pixel. The object-oriented classification includes two consecutive processes. An image is subdivided into separated regions according to the spectral and spatial heterogeneity in the image segmentation process. Then the objects are assigned to a specific class according to the classs detailed description in the image classification process. As a case study, the study area is a pail of the planning Beijing Olympic Games Cottage, which has changed greatly with the advent of the year of 2008. The panchromatic SPOT-5 image in August of 2002 is segmented and these segments then are classified to hierarchically linked objects by the eCognition software. The overall classification accuracy is up to 87%

Early warning monitoring and management of disasters

Everyone would admit that disaster early warning is more important than later treatment and damage repair. If an effective tsunami early warning system had been in place in the Indian Ocean region on 26 December 2004, thousands of lives would have been saved. The same stark lesson can be drawn from other disasters that have killed tens of thousands of people in the past few years. Effective early warning systems not only save lives but also help protect livelihoods and assets created by national development. This paper addresses the issue of disaster early warning monitoring and management in a systemic manner and offers a general approach to a management solution. From the viewpoint of control theory, it depicts the disaster early warning monitoring and management as an information chain which has five links: disaster model bank link, disaster monitoring network link, disaster transmission channel, disaster analysis and management link and decision making and commanding link. The five links constitute an information loop, with disaster data being collected, processed through the chain and control information being fed back to the different links. With some vivid examples, this paper indicates the weakness of current links in the existing disaster early warning and management systems. On the basis of all the above analyses, the paper finally puts forward some suggestions in order to improve the performance of early warning monitoring and management of disasters.

Simulation study of underwater passive navigation system based on gravity gradient

Gravity gradient based passive navigation for autonomous underwater vehicle (AUV) is proposed in this paper. Its basic principle and two working modes are analyzed in detail. Simulation test has been done and the results show that the proposed method can provide high precision positioning information for AUV

Decision-making modeling method based on artificial neural network and data envelopment analysis

When people make use of the limited, expensive and historical data to build multiple-input and multiple-output nonlinear mathematical model for decision-making, they often face the problems whether or not all of the experimental data can be used directly for modeling, although artificial neural network (ANN) is a good method to describe the non-linear relationship between inputs and outputs. In the paper, decision-making modeling method based on feed forward ANN and data envelopment analysis (DEA) is brought forward. Experimental data were evaluated and projected by DEA, a widely used method to evaluate relative efficiency among decision making units (DMU). Then the experimental data would become more scientific and reasonable, and all of them could be used for decision-making modeling of ANN. Experiments show that the model of ANN, which gained by training these data, is DEA effective. So it is a new method for optimal data utilizing and decision-making modeling. The method is useful to the research, which may only get limited and high cost data after several times or several years of experiments.

LBS based disaster and emergency management

In recent years, with the occurrence of more and more natural disasters and emergencies, China has also been greatly affected by that without exception. Wireless communication technology is playing an important role in disaster and emergency management. In current applications, mobile communication network, as the main key technology, have been used to deal with disasters and emergencies. However, mobile communication network application will be subject to certain restrictions when ground communication facilities are severely destroyed. In response to this situation, a new solution need to be worked out and a platform for disaster and emergency management should be built. The most important technology in the solution is Location Based Service, which is based on satellite communication and wireless communication. In this paper, the components of LBS and their applications in disaster and emergency were discussed. Meanwhile, the overall framework and function modules of the disaster and emergency management system were given. There are two main communication forms in response to different circumstances: the first one mostly depends on wireless communication; the other one relies on satellite communication, satellite communication (such as communication satellites and COMPASS system) would be an alternative method when wireless network is useless. COMPASS system is compatible with positioning and simple communicating function, which can play great role when communication satellites are busy or blocked. At the same time, tasks can be allocated to mobile users and managed by disaster and emergency management center. It can also receive data of multitudinous formats transferred from mobile user. Many tests approached under the platform proved that it is a useful solution for disaster and emergency management.

Simulation design of underwater terrain matching navigation based on information fusion

The data preprocessing, algorithm analysis and performance evaluation were done making full use of various information related to the ocean geographical features, then intelligent data fusion was used to design the underwater passive navigation system simulation module. Simulation results show that the underwater terrain matching assisted navigation can modify the error from inertial navigation system and provide precise navigation for underwater navigation system

Spatial temporal geographic ontology

Ontology is the branch of metaphysics that deals with the nature of being. Ontology is currently used by philosophers, information scientists and psychologists. A sharing ontology is required for communicating between the communicating participants. And the formal description of ontology is fundamental to data exchange standards. In recent years, ontology has been used by geographers. Many researchers have recognized the importance of geographic categories, and the relationships and interactions between geographic categories. Geographic objects are intrinsically tied to space and exist at some time. In the geographic realm, cognitive categories expose certain special features of geographic objects at surveyable scale. And that these features denote the specific ontological characteristics of geographical objects. At the same time, there has been an increasing awareness of the importance of time, and time has been an integral part of geographical information science. Thus, the research of geographic ontology must involve a fully spatio- temporal view of our world, in other words, it is about spatial temporal geographic ontology. In this paper, firstly, it reviews the recently research of geographic ontology of many experts. And it mainly explores that what is the geographic ontology and what are the research contents of geographic ontology, and how to construct an geographic ontology? The domain of geographic ontology contains objects, relations, boundaries, events, processes, qualities, and quantities of all sorts. Geographic objects are typically complex, and they will in every case have parts. An adequate ontology of geographic objects must therefore contain a theory of part and whole, or mereology. And that an adequate ontology of geographic objects must contain also a topology, a theory of boundaries and interiors, of connectedness and separation, that is integrated with a mereological theory of parts and wholes. Secondly, the paper investigates the three levels of reality: the spatial reality, the cognitive reality and geographic reality. Then it considers that geographic cognition is the key factor of geographic category. Geographic categories are related to natural, cultural, and fiat element, et al. Thirdly, in this section, the research is about an spatial temporal geographic ontology that contains space and time. The paper discusses the spatial classification and the temporal categories of geographic phenomena. Spatial objects based on object or field, which are continuants or discrete, must be represented suitably by geographic ontology. Temporal analogue of objects: there are events and processes of various kinds. Processes and events are the key elements that describe dynamic action of spatial temporal geographic objects. With the introduction of time, the requirement to take heed of the manifold interconnections between the spatial and the temporal must be proposed. The geographic phenomena can be represented as spatial or temporal, and as continuants or discrete, and as events or processes. These categories are not exist in isolation from one another. Spatial and temporal are restricted each other and represent the dynamic geographical phenomena all together. Lastly, the paper concludes that spatial temporal geographic ontology must take heed of the manifold interconnections between the spatial and the temporal and in the future a technical infrastructure be needed to provide a basis for GIS.

Study on data fusion method in geographic information system for transportation

In order to make it convenient for sharing and maintaining data, this paper structures the independent real-time traffic information database, seamless merging real-time traffic information and GIS data through data fusion method. In order to realize this purpose, a unified base-line net is set up in the traffic information data model. Base-line net is composed of base points and base lines.

Comparison of pixel-based fusion between multispectral data and high spatial resolution data

In the paper, experiments and analysis of three pixel-based fusion methods had been discussed. The fusion methods include IHS, PCA and Brovey transform method. The fusion experiments were carried out in two circs, that is, between Landsat TM multi-spectral data and SPOT-4 Pan data, Landsat TM multi-spectral data and IRS-C Pan data. From the fusion results, the definition of all fusion images were improved greatly compared to the Landsat TM image. Especially the linear ground objects are much clear, such as the roads, the residents, the bridges, etc. According to the fusion between Landsat TM data and SPOT-4 Pan data, the Brovey fusion method was the best one. The PCA fusion method was better than the IHS fusion method. According to the fusion between Landsat TM data and IRS-C Pan data, the Brovey fusion method was also the best one. But the IHS fusion method was better than the PCA fusion method. Maximum likelihood method of classification was carried out on the fusion result, and classification accuracy of the classification results were evaluated. From the evaluation result, it can be concluded that classification accuracy of the Brovey fusion result is the highest between Landsat TM data and IRS-C Pan data. Classification accuracy of the IHS fusion result is the highest between Landsat TM data and SPOT-4 Pan data.

Effect of precipitation on ocean wind scatterometry

This paper presents preliminary results of precipitation effect on microwave scatterometry wind estimates at C and Ku band. The results show that microwave scatterometer underestimates the wind speed by up to 10 m/s for rain rate condition of 15 mm/hr and wind speed condition of 25 to 30 m/s for both frequency bands