Guoyin Cai

Monitoring of urban heat island effect in Beijing combining ASTER and TM data

This paper focuses on the monitoring of the urban heat island (UHI) effect with temporal and spatial variation, combining Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Thematic Mapper (TM) data. Our study area is located in the central urban area of Beijing, which mainly refers to the areas within the fifth ring road. For detecting UHI changes over the years 2002–2006, three ASTER images in the summers of 2003, 2004 and 2006 and two TM datasets in the summers of 2002 and 2005 were collected. For monitoring UHI changes with the seasons, three ASTER images and one TM image in 2004 in winter, spring, summer and autumn, respectively, were employed. To calculate the urban heat island intensity, the land surface temperatures were retrieved iteratively for ASTER data and using a generalized single-channel method for the TM image. Four separated regions located in four directions outside the fifth ring road were selected as representing rural comparative regions. Their averaged land surface temperature was regarded as the rural comparative temperature. The UHI intensity was computed by the difference between the pixel urban land surface temperature in the urban area and the comparative temperature in the rural area. Detection of the UHI effect over 2002 to 2006 indicated that most of the areas with high UHI effect were the industrial land use regions and the areas having a high density of buildings, roads, transportations and residents; and the areas without UHI effect were located around the regions with large areas of grassland, trees and water bodies. Our results also showed that the UHI effect was not proportional to urbanization over time. Statistical UHI data during 20 July to 20 September in 2003–2008 also support this point. The monitoring of the UHI effect over seasons (winter, spring, summer and autumn) showed that the urban area of Beijing city had a high UHI effect except in winter, when the urban area of Beijing was in an urban heat sink; the UHI effect increased in spring, summer and autumn.

Iterative self‐consistent approach for Earth surface temperature determination

The split‐window method is used widely for Earth surface temperature determination from remotely sensed data. The split‐window coefficients depend on the surface emissivities, atmospheric absorption coefficients and total water vapour amount. It is always a challenge to obtain the local split‐window coefficients for the land surface. An iterative self‐consistent approach has been used previously for studying atmospheric effects in optical scanner data for the oceans. This Letter presents a similar approach for Earth surface temperatures. The method can be used for Along‐Track Scanning Radiometer (ATSR) thermal infrared data to derive the localized split‐window coefficients, which are a function of space and time of surface emissivity, radiative forcing, etc., especially for land surface areas.

Preliminary Study on Unsupervised Classification of Remotely Sensed Images on the Grid

Grid is a new technology. With corresponding middleware it can give strong computing power. In this paper we mainly discuss the middleware technology and architecture used in remote sensing image classification algorithm. Because unsupervised classification middleware is the key of the classification middleware algorithms, we study the alternant-unsupervised middleware and put forward a non-alternant unsupervised middleware scheme. Based on this scheme, main factors which effect the performance of non-alternant unsupervised classification are analyzed.

Experience of Remote Sensing Information Modelling with Grid Computing

In this paper, we focused on the remote sensing information modeling and determination using Grid computing platform. We have underdone the experiments using remotely sensed images for thermal inertial modeling in Condor system that is one of the Grid Projects existed nowadays worldwide. We divided remote sensing data into several parts and run them on Condor pool and on one single machine. From these tests, the relationship among the work efficiency of image processing in Condor system and the number of the separated parts of image and the number of machines in this system is presented. Given a certain number of machines, a most efficient image size is existed among varies sized images. Besides, the possible causes of the longer put-off in this process are given, and some possible methods to resolve this problem are also presented. It is feasible to use Grid computing system such as Condor to process remote sensing data. And if the postpone problem can be resolved, the work efficiency of Grid systems will be high. Even with so many problems, it is a good thing that Grid systems do many things for you during all of us are in sleep. Our next major task will concentrate on realizing an arithmetic that can read and divide remote sensing images based on image size and number of machines in Grid system automatically, and transfer results back to the submitted machine as a whole data file.

Reconstruction of 3D Curvilinear Wireframe Model from 2D Orthographic Views

An approach for reconstructing wireframe models of curvilinear objects from three orthographic views is discussed. Our main stress is on the method of generating three-dimensional (3D) conic edges from two-dimensional (2D) projection conic curves, which is the pivotal work for reconstructing curvilinear objects from three orthographic views. In order to generate 3D conic edges, a five-point method is firstly utilized to obtain the algebraic representations of all 2D projection curves in each view, and then all algebraic forms are converted to the corresponding geometric forms analytically. Thus the locus of a 3D conic edge can be derived from the geometric forms of the relevant conic curves in three views. Finally, the wireframe model is created after eliminating all redundant elements generated in previous reconstruction process. The approach extends the range of objects to be reconstructed and imposes no restriction on the axis of the quadric surface.

A remote sensing application workflow and its implementation in remote sensing service grid node

In this article we describe a remote sensing application workflow in building a Remote Sensing Information Analysis and Service Grid Node at Institute of Remote Sensing Applications based on the Condor platform. The goal of the Node is to make good use of physically distributed resources in the field of remote sensing science such as data, models and algorithms, and computing resource left unused on Internet. Implementing it we use workflow technology to manage the node, control resources, and make traditional algorithms as a Grid service. We use web service technology to communicate with Spatial Information Grid (SIG) and other Grid systems. We use JSP technology to provide an independent portal. Finally, the current status of this ongoing work is described.

Java-Based grid service spread and implementation in remote sensing applications

Remote sensing applications often concern very large volumes of spatio-temporal data, the emerging Grid computing technologies bring an effective solution to this problem. The Open Grid Services Architecture (OGSA) treats Grid as the aggregate of Grid service, which is extension of Web Service. It defines standard mechanisms for creating, naming, and discovering transient Grid service instances; provides location transparency and multiple protocol bindings for service instances; and supports integration with underlying native platform facilities. It is not effective used in data-intensive computing such as remote sensing applications because its foundation, Web Service, is not efficient in scientific computing. How to increase the efficiency of the grid services for a scientific computing? This paper proposes a mechanism Grid service spread (GSS), which dynamically replant a Grid service from a Grid node to the others. We have more computers to provide the same function, so less time can be spent completing a problem than original Grid system. This paper also provides the solution how to adept the service duplicate for the destination node’s Grid environment; how each service duplicate communicates with each other; how to manage the lifecycle of services spread etc. The efficiency of this solution through a remote sensing application of NDVI computing is demonstrated. It shows that this method is more efficient for processing huge amount of remotely sensed data.

High throughput computing for spatial information processing (HIT-SIP) system on grid platform

For many remote sensing application projects, the quality of the research or the product is heavily dependent upon the quantity of computing cycles available. Middleware is software that connects two or more otherwise separate applications across the Internet or local area networks. In this paper, we present the High Throughput Computing Spatial Information Processing (HIT-SIP) System (Prototype), which is developed in Institute of Remote Sensing Applications, Chinese Academy of Sciences, China. Several middleware packages developed in the HIT-SIP system are demonstrated. Our experience shows that it is feasible that our grid computing testbed can be used to do remote sensing information analysis.

Feasibility Study of Geo-spatial Analysis Using Grid Computing

Spatial applications will gain high complexity as the volume of spatial data increases rapidly. A suitable data processing and computing infrastructure for spatial applications needs to be established. Over the past decade, grid has become a powerful computing environment for data intensive and computing intensive applications. In this paper, we tested and analyzed the feasibility of using Grid platform for spatial analysis functionalities in Geographic Information System (GIS). We found that spatial interpolation, buffers, and spatial query can be easily migrated to Grid platform. Polygon overlay and transformation could achieve better results on Grid platform. To do network analysis and spatial statistical analysis on Grid platform could be no significant improvement of performance. The most un-suitable spatial analysis on Grid platform is the spatial measurement.

Soil moisture retrieval from MODIS data in northern china plain using thermal inertia model (SoA-TI)

Soil moisture plays an important role in monitoring of drought and waterlogging. In this paper, a thermal inertia map was obtained from MODIS data on April 16, 2004 using SoA-TI model in Northern China Plain covering Latitude from 38.5°N to 40.5°N and Longitude from 115°E to 117.5°E. A soil moisture map was obtained based on the relationship between thermal inertia and soil moisture. And a distributive map of drought and waterlogging was obtained based on the relationship between ranks of drought and soil moisture. The drought map derived from MODIS data shows that most of the studied area was in a drought condition except the eastern littoral area where the soil moisture was in order. Generally speaking, the Northern China Plain was generally in a drought condition on April 16, 2004. The actual drought information obtained from the official website of Beijing Meteorological Bureau indicates that it was in a drought condition in Northern China Plain in the middle ten days of April. The result derived from MODIS data using SoA-TI model is in consistent with the actual situation. It indicates that it is an effective way to monitor regional drought and waterlogging by means of deriving soil moisture using SoA-TI model from MODIS data.