Surface net radiation is the sum of incident downward and upward shortwave and longwave radiation. Changes of surface net radiation control the Earth's climate, the hydrological cycle, and plant productivity. In this paper we focused on the spatio-temporal variation analysis of surface net radiation over China at site-scale. We estimated the parameters of the FAO Penman model using daily surface net radiation of 53 radiation sites during1993-2010 over China, and then we calculated mean annual/seasonal surface net radiation data in 699 weather sites from 1961-2010, based on the model and long-term measurement data of these stations. Furthermore, we analyzed the spatio-temporal variation characteristics of mean annual/seasonal surface net radiation of 699 sites in China in recent 50 years, by means of Mann-Kendall trend analysis method and GIS spatial analysis technique. We concluded that: 1) Parameterization of the FAO Penman model shows that the model has a relatively high simulation accuracy with RMSE 27.9W/m2, the coefficient of correlation 0.85, and the mean relative error 13%; 2) Mean annual/seasonal surface net radiation over China declines visibly with a fluctuant process with the changing rate reaching 0.74 W/m2 every 10 years. The amplitudes of changes vary with the seasons with the maximum downtrend (1.93 W/m2 every 10 years) in summer; 3) The analysis at each site shows that mean annual surface net radiation declines significantly (α=0.05) in most sites (59.8%). The changing trend of the eastern part is more obvious than that in the western part and summer plays the most important role in the interannual variability of surface net radiation. Northern China, Central China and Southern China are decreasing regions in spring, summer and autumn, while the Qinghai-Tibet Plateau turns to be a noticeable decreasing zone in winter. We speculated the much heavier aerosol loading in eastern part of China should be the primary cause for the decrease in surface net radiation and the volcano aerosols contribute to the oscillation in the trend. The increasing trend of snow on the Qinghai-Tibet Plateau should account for the decreasing trend of surface net radiation in winter. The quantitative spatio-temporal analysis of surface net radiation will be vital for the climate change and terrestrial ecosystem evapotranspiration research.
The process of population agglomeration/shrinking and changes in spatial pattern are the most intuitive presentation of the spatial distribution of population. This study focused on the pattern of population agglomeration/shrinking and the overall population evolution trend. In view of this, we took the Beijing-Tianjin-Hebei Metropolitan Region as an example, based on 1982-2010 census data, using the degree of concentration of the population, population increase-decrease change, population migration methods, quantitatively studied the process of population agglomeration/shrinking and changes of spatial pattern in Beijing-Tianjin-Hebei Metropolitan Region. The study shows that the total population continues to grow, but rendering uneven growth in over different areas during nearly 30 years in the Beijing-Tianjin-Hebei Metropolitan Region. The regional distribution differences of population are obvious, especially between north to south, east to west of Beijing-Tianjin-Hebei Metropolitan Region. Population increase is a main character, more than 80% of the counties possessing a population growth, reflecting the effect of population concentration. Population decrease is just scattered, less than 20% of the counties possessing a population decrease. The population flow is more frequent in the Beijing-Tianjin-Hebei Metropolitan Region. Population flow into the region is located in the urban areas of Beijing, Tianjin and Hebei. Population outflow is mainly from the impoverished mountainous counties of Zhangjiakou and Chengde. Both the static demographic indicators and the dynamic analysis method show that the population agglomeration/shrinking and changes of spatial pattern are very obvious. The Beijing-Tianjin-Hebei Metropolitan Region has already formed the Beijing, Tianjin, Shijiazhuang and other cities as the centers, holding population flow from adjacent counties, i.e., presenting a multi-center structure of population distribution.
Small-area population space-time distribution is the key point to urban planning, administration and warning for emergency. How to get the data of population distribution becomes the urgent task. While the urban buildings are the main place bearing population, it is necessary and meaningful to find and use the relationship between urban population and urban buildings. In this paper, buildings are extracted with high-resolution remote sensing images, and then a classification system of building functions is established. Based on the classification system, the extracted buildings are classified to 16 classes such as residential, office, financial, leisure, school, catering, accommodation, medical, business, comprehensive and then accommodating capacity coefficients of the buildings are estimated. Based on the survey and existing papers, population-attracting rate curve of buildings of all kinds of function are described. Model of space-time distribution of people is built to simulate the population distribution in Donghuamen Subdistrict of Beijing's Dongcheng District. According to the results of the simulation, the total capacity of all buildings in the target region is 693 thousands. The population distribution of 0:00, 6:00, 7:00, 8:00, 9:00, 10:00, 11:00, 12:00, 13:00, 14:00, 15:00, 16:00, 17:00, 18:00, 19:00 and 22:00 are simulated and exhibited in this paper. In order to make the results clearer, the region is divided into smaller regions: A, B, C and D, and the population quantity changes of the four regions are described as curves. Then reasons for the changes are analyzed. In the end, improvement methods for the research are discussed, i.e., finer classification system of building functions, a finer urban population bearing units classification, and a finer population-attracting rate curve of buildings.
Transportation and land use is an interactive dynamic process. Urban and regional development is greatly affected by the transportation infrastructure. Transportation-induced development plays an important role on the regional development and urban planning. Quatitative assessment of urban transportation infrastructure and its effects on regional development is essential to promote future urban planning and sustainable development. Yancheng, a coastal city in Jiangsu Province of China, is chosen as the study area. A research framework is developed to evaluate the spatial effects of transportation-induced development in Yancheng over the past 20 years. Firstly, series of land use mapping based on the 1990, 2000, 2010 Landsat TM images classification are acquired through data pre-processing and image classification. Secondly, buffer analysis based on lines and points with the proposed distances are implemented on different transportation infrastructure such as G204 Road, G15 Shenghai Highway and Xinchang Railway. Thirdly, the spatio-temporal change in land use in the proposed buffer zones along the major roads and surrounding their major exits are acquired through the overlay analysis. Fourth and Finally, the statistical analysis are performed to obtain the major urban transportaion infrastructure and its effects on the surrouding land use. In the technical work, a geoprocessing model is developed to evaluate the major road impacts on the urban and regional development based on Model Builder moduler. Such a geoprocessing model can effecitively used to select the optimal buffer distance around a line or a point. The follow-up calculation and analysis are based on the proposed buffer anlysis. In this study, the best buffer distance along the major roads is 5km in both sides, and the best buffer distance surrounding the exits of major roads is 10km. The results show that such a spatial analysis perspective is a novel way to evaluate the transportation-induced urban and regional development. The land use type from cropland to construction land along the major roads is changed rapidly, especially since 2000. The cumulative land use change is very significant along the major roads, particularly along the new-built G15 Shenghai Highway.
In the representation and communication of geographical knowledge of human beings, locations are often textually expressed. In addition to place names and addresses, a spatial assertion, which consists of reference objects and spatial relations, can roughly describe a locality. Typical examples of spatial assertions are "the vicinity of Peking University" and "Between Peking University and Tsinghua University". The objective of spatial positioning is to infer the location of a target object and the associated uncertainty for a given spatial assertion. In this research, we investigate four levels of uncertainty associated with spatial assertions. They are uncertainty of spatial assertions, imperfection of reference objects, imprecision and vagueness of spatial relations, and distribution of target objects. If a target object is abstracted to a point, the concept of an uncertainty field can be used to represent the possible spatial distribution of the target object. An uncertainty field is a 2-dimensional probability density function that satisfies 45p(x,y)dxdy=1 where denotes the field and F is its support. For a point T and a reference object A, if the probability that an observer make a description X is high, then the probability density at O is also high when X is known. This argument is proved using Bayes' theorem and can be viewed as the theoretical foundation to establish an uncertainty field. We also implemented a toolkit to generate uncertainty fields based on a number of spatial assertions.
For a long time, the study of 3D geological modeling relies on using exploration data from drill holes or geologic sections. But, on the premise of the lack of large area general geological background modeling, only considering of local region refined modeling often lead to overgeneralization and over-reliance on the data. Plane geological map, which integrates geological field survey and the results of the work with geological expert knowledge, reveals rock stratigraphy and geological structure of the region, is the available and the most direct data source for 3D geological modeling. On the premise of the lack of other geological data, using planar geological map to build 3D geological model is an effective solution. The 3D geological modeling directly based on planar geological map, but it is weak in controllability and the building quality of the geological models is unsatisfactory. To solve this problem, this article proposed a new 3D geological modeling method based on geological plane maps and used cutting profile as the intermediary. The method encrypted the existing data of the study area indirectly, processed complex structures such as folds using cubic spline fitting combining with artificial revision, and realized the automatic drawing of cutting profile based on the geological plane maps. We took regular voxels as the 3D spatial data model, got a series of parallel cutting profile of the study area automatically drawn, and built a rasterized 3D geological model. With Xinggang area, Chongqing City as the study area, the prototype experiment system was built and we verified the effectiveness and practicality. Results showed that the 3D geological modeling method based on geological plane maps is an effective solution to build regional 3D geological model under the condition of lacking of other geological data.
Real time and rapid simplification of large-scale data, required by personalized WebGIS service which is based on vector data, becomes more and more important. The study was based on Douglas-Peucker, one of classical curve simplification algorithms, but in the view of its low performance, it can hardly simplify large-scale data in real time and rapidly. At the same time, the development of cloud-computing offers new storage technologies and computational methods for real time and rapid simplification of large-scale data. So this study made use of hadoop, one of the open source cloud computing platforms, to design and realize multi-machine parallel Douglas-Peucker algorithm. In the algorithm, we deigned the logic slices of data, and assigned the slices to the clusters by MapReduce computing model, achieved parallel simplification. In order to verify the efficiency of the algorithm, we designed the experiments and compared the efficiency of traditional DP algorithm and multi-machine parallel DP algorithm in tow aspects: 1) the same threshold and different amount of data; and 2) the fixed amount of data and different thresholds. The result of the experiments showed: the multi-machine parallel DP algorithm was more efficient than tradition DP algorithm for large-scale data and high-complexity computing. In this case, the data processing time was much longer than the data allocated in the inter-cluster and the transmission time, and every node was involved in a certain operation, improved the efficiency of operations. But for small scale data and low-complexity computing, the advantage of multi-machine parallel DP algorithm was non-obvious. Mainly due to a part of the nodes didn't participate in the operation, the computing potential of the cluster was not full play, while the data processing required time was very short, so the data allocation and transmission time impacted obviously. And, in order to meet the real time and rapid simplification of large-scale data, the multi-machine parallel DP algorithm should choose the appropriate simplification method for different amount of data and complexity computing in future.
Gully feature points (GFPs) are crucial for studies on spatial pattern and evolution of gully landforms, and the extraction of the GFPs is the basis of related researches. Previously, scholars have made different methods for GFP detection and most are about runoff nodes. However, these methods are still not integral and have deficiencies in either accuracy or computational efficiency as analyzed in this paper. Thus, based on detailed analysis of DEMs and their derivatives, a series of new algorithms are proposed to improve the performance of GFP detection (including runoff nodes, river heads, confluence origins, potential knickpoints and outlets) by trace of flow direction and neighborhood feature judgment. The methods examine the essential features of GFPs and most thresholds used are invariable in different kinds of landforms. Thus, both the robustness and efficiency of the extraction are improved by the new algorithms. As orders of nodes and knickpoints are important in further analyses, criteria for automatic order classification are also established based on Strahler rules. By using 5m resolution DEMs in the test area in Yijun County, Shaanxi Province, experiments are made to test the methods' ability in both GPF extraction and classification. The results of runoff nodes, river heads, confluence origins and outlets are consistent with manual marks. The detected potential knickpoints also create favorable conditions for researches on gully evolution and guarantee the integrity of GFPs to the maximum extent. Preliminary analyses are made using the GFP results and reflect the variation characteristics of the sum of GFPs as rainfall changes. Finally, the impact of watershed completeness on the accuracy of GFP extraction is discussed in details. It shows that both the loss of stream pixels and confluence accumulations could cause the omission of the points. As the influences brought by data incompleteness can hardly be removed in the extraction process, it is crucial to guarantee that the boundaries of watersheds are within the data extent.
The basic attribute of flood submergence contains the inundated area and depth which are the core factors in flood disaster. The accurate and efficient obtaining of inundated area is critical for flood assessment and disaster relief. In recent years, forecasting and simulating the flood inundated area has been a hot topic in applied hydrology of GIS by using digital elevation model (DEM) data. However, it is always more difficult to get the inundated area and depth of flood submergence and normally needs more computing time to calculate the inundated area and depth since large study area and huge data. According to the disadvantage of existing method in computation speed and accuracy, a fast and accurate method for flood submerged area extraction is provided in this paper. Firstly, the distortion terrain when describing the discontinuous terrain such as ditch and dike by regular grid DEM is revised by taking the advantage of terrain features preserved grid digital elevation model (F-DEM). After corrected, flood submerged surface is created according to the Kriging interpolation model based on monitored points of flood. At last, combined with the basic principle of flood submerged extraction, the true area of flood submergence is obtained by using analysis techniques of overlay and topology spatial location in GIS. Based on the data of monitoring points in Shuitou Town, Wenzhou City, the flood inundated area is analyzed. And, the efficiency of the extraction method is tested by the monitoring points of simulation level in a large area. The experiment results show that:(1) The extraction method works well in the discontinuous terrain such as ditch, farmland and dike and the connectivity of submergence could be maintained effectively. (2) Calculating the connectivity of submerging is the most time-consuming part of the submerged area extraction. Compared with seed filling algorithm, the computational efficiency of the method in this paper rises by 90%. All in all, this extraction method has the ideal precision and efficiency which can better solve the inundated area extraction issue and provides scientific assessment for flood estimation and disaster relief.
Base on Digital Line Graphic (DLG) at 1:100,000 scale and Digital Elevation Model (DEM: 30×30 m resolution), firstly, the geomorphological types of Fujian Province can be divided into two basic types according to the two main combinational indicators slope and area: shallow-slope region and hill-mountain (steep-slope) region. Secondly, the elevational points that contours the river system in DLG are extracted by ArcGIS software. On this basis, the relative reference surface of Fujian Province is constructed through spacial interpolation method. Thirdly, geomorphological entities in steep-slope region are divided into taper units with the method of watershed hydrological model. Finally, according to the 1:1,000,000 Geomorphological Mapping Specification for China, combining the geomorphological characteristics of Fujian Province, and overlaying the above-mentioned geomorphological entities and relative reference surface of Fujian Province respectively, the geomorphological entities of Fujian Province can be divided into six types, i.e., plain, platform, low relief hill, high relief hill, low relief mountain and intermediate relief mountain. The result shows: among geomorphological types of Fujian Province, hill accounts for 34.1%, mountain accounts for 51.8%, both together account for 85.9%, and plain, flat and platform together account for only 13.1%. The result is basically identical to that by traditional manual mapping. The methods developed in this article are corresponding to traditional classification system of geomorphology for Fujian, and can automatically classify the geomorphological entities fast and well, such as the shallow-slope region and hill-mountain region, plain and platform, which are feasible according to precision and efficiency, saving manpower, material resources and financial resources greatly, and offering a new thinking and methodology for domestic and international similar researches.
In order to realize digitized, intellectualized and automated mineralization prospect forecast appraisal, first we carried out mineralize prospect quota forecast appraisal question decomposition under the GIS environment, based on data-driven and knowledge-driven approaches such as the evidence weighted method and information mensuration, to realize geological variable screening and Layer through the ArcGIS space analysis model builder, as well as get the comprehensive information prospecting geologic model and information mensuration or evidence weighted quantitative model by the layout description. Next, to the geological variable characteristic, different mathematical quantification method, unit division and the evaluation method and so on, through analysis and comparison under the GIS environment, proposed simultaneously the rule grid (surface shape) or the equal grid center (point shape) as the basic unit, important method, central point method, area method and corresponding"0 or 1"two-state evaluations as recognition variable existence or not through ArcGIS space analysis modelling realization. Thirdly, based on the variable standardization transformation and the multi-dimensional space linearity mapping quantitative evaluation model, we overcomed the influence of geological variables, which, are not equal and not independent, to the appraisal. On that basis, taking the map of Dashen sheet in Wuyishan metallogenic belt of scale 1:50000 as the experimental plot, applying ArcGIS Model Builder method, we finally established the ArcGIS space analysis model on iron, copper, lead-zinc mineralization prospect quota forecast appraisal, selected 12 prospect areas, which included 3 areas of class A, 3 of class B and 6 of class C. The forecast result is basiclly consistent with that of the information mensuration and evidence weighted method.
SOLAP is based on the spatial data warehouse and is a kind of on-line spatial data access and analysis for a specific problem. The premise of implementation of SOLAP is to solve the integration problems between the spatial data and non-spatial data in spatial data warehouse. First, the authors analyzed the advantages and disadvantages of the atomic level architectures and the bus architecture of data warehouse, and put forward the hybrid data warehouse architecture. We discussed the hybrid data warehouse architecture model, used the multilayer system artchitecture, and put forward a kind of environment datasets-oriented spatial OLAP system framework, including the production database layer, data warehouse layer (basic business database-subject database)-middleware layer and Business Intellegence (BI) comprehensive analysis layer as well. The production database layer is the basic database for supporting various operations in environmental protection. The data warehouse layer includes the basic business database and the subject data warehouse. The fusion middleware layer mainly includes BI server, Presentation Server and MapViewer Server, that is the B I business logic laye between the application layer and the data warehouse layer. The BI comprehensive analysis layer provides all kinds of query analysis through the interaction between the middleware layer and the data warehouse layer. Then, we analyzed the environmental data integration and spatial data warehouse modeling process, and achieved environmental attribute data integration, which used PowerDesinger 12.5 for data modeling, used Oracle 11g to build environmental spatial data warehouse, and used the Oracle Data Integrator tools. We analyzed and constructed the environmental data spatial dimension extension method and model, which extended the administrative divisions dimension table. We used the Oracle Spatial sdo_geometry abstract data type to realize spatial environment data storage, spatial data and data warehouse data integration storage. And, the integration problem was discussed between OLAP and GIS. The authors implemented the fully integration between OLAP and GIS which uses OBIEE as a OLAP tool, Oracle Mapviewer as GIS component. The GIS service and OLAP service were integrated at the Web server to provide a unified access interface. In the end, the environmental datasets SOLAP prototype system was implemented, which validated the SOLAP framework and the system model.
The traditional multimedia map, which combines map and multimedia elements, represents the geographic world more visually. With the rapid advance of the multimedia and position technology, the new-style geo-tagged media, such as geographic video, panoramic picture and measurable image, have been introduced in GIS applications. This paper aims to introduce the stereo video to GIS. Geographic stereo video includes both spatial and temporal geographic characteristics acquired through ground-based or non-ground-based cameras. It is the stereo video that extends the elements of interior and exterior orientation for video frame. Therefore, it supports the video retrieval and image measurement based on the spatial information, And it has been a new way for geographic representation. With the wide application of web service technology, geographic stereo video web service will further expand the video GIS application. To fully utilize the geographic stereo video resource in web environment, this paper aims to design a framework of geographic stereo video web services and to develop the related RESTful web interfaces. Based on the discussion of functional requirements such as visualization, querying and measurement, a web service framework composed of data layer, service layer and presentation layer for geographic stereo videos is introduced. All functions are packaged as a service in this framework and its communication are based on a unified interface, standard protocol and universal data format. The video URI resources, its representation format and related operation interfaces are defined carefully as the RESTful web services. The client-server interaction mechanisms for video querying, video displaying and image measurement are outlined in details. All the geographic stereo video web services are implemented on the basis of Windows Communication Foundation (WCF) and ArcGIS Server technologies. Based on the geographic stereo video service and browser-side AJAX (Asynchronous JavaScript and XML) programming, a prototype system of geographic stereo video web service for Henan University (Jinming campus) was developed. The prototype application shows that the service framework and system design introduced in this paper is feasible and adequate for video GIS application development. It is of reference value for web service standardization of new-style geo-tagged media.
Under the three-dimensional (3D) tendency in land-use, the two-dimension (2D) cadastre management model can not reflect the land-use of the vertical space and the property. It is essential to introduce the 3D cadastre management model. The previous scholars didn't put the relation between people, right and land administrative unit into consideration. This article analyzed the core classes of LADM in ISO/TC211, including LA_Party, LA_RRR, LA_BAUnit and LA_SpatialUnit, and their relationship. LADM get a thought of constructing administration units and space units separately. This allows for a separate introduction in LADM of the "legal/administrative part" (the registers) and of the "spatial part" (the cadastral map), e.g. first the registers, then the map. Considering the framework of LADM's core classes and the design concept of it, choosing a hybrid solution of combined 3D cadastre and 2D cadastre, the 3D cadastre concept model which is suitable for the current situation in China was proposed. In this model, the basic administrative unit consists of 2D and 3D entity of right, and the spatial unit consists of 2D space object and 3D space object, so there is a relationship of one-to-one between them. In order to meet the management need of land's spatial right, the model introduced the core class LA_SpatialUnit which covers building units, networks and other 3D cadastre forms. And based on facial model theory and the object-oriented thought, the data model of spatial unit was constructed. According to the concept model and spatial data model of the 3D cadastre, the 3D cadastre management model was designed and its prototype system was developed to verify the model's feasibility. Through the instance of the management of house property right units in Shenghe garden district and underground land parcel which locates in a commercial district, the model is confirmed to be viable in the 3D cadastre management in our country.
Geological map, as an efficient tool to present and summarize geological survey results, is a kind of geological information indispensable for economic and social development, and has attracted great attention from the government and the public all over the world. Qingdao Institute of Marine Geology has been complicating the serial maps of geology and geophysics on China Seas and Land on the scale of 1:5M since 2008. It is important to compile a piece of map including Chinese mainland and China Seas and the adjacent land and sea area. The serial maps compilation was under guidance of block tectonics, and based on various data and survey results of geology and geophysics on China seas and land over the past sixty years. The compilation has three main purposes: realizing the splice that includes theoretical basis, technology and method of maps of geology and geophysics on China seas and land; reflecting the status of survey and research of basic geology and tectonic framework of the study area; and exhibiting the growth, development and collision of different blocks and the formation of Pangea on China seas and land since Paleozoic, revealing emphatically the evaluation process of Chinese mainland that from "higher in the east, lower in the west" to "higher in the west, lower in the east" since the Indo-China movement. The serial maps can provide service to geological work deployment which would be helpful for the policy-making body. Meanwhile, the serial maps can also be used as a basic map for mineral resources exploration and resources and environment studies. And, the methods we used in the compilation of the serial maps are introduced as a new try to solve the problems we had met.
Traditional electronic map, which is based on ArcGIS API for Flex, just navigates to the geometric center of the target building, but the positioning accuracy of the specific unit inside the building is not enough. To update and maintain spatial data, administrators must resort to map editing software as well as ArcGIS Server. Further more, with 360-degree Virtual navigation in the digital campus becoming a research hotspot, massive data will inevitably increase the burden of the system and reduce the loading speed. To this end, in this article we proposed a method on the precise geolocation network using, in order to make the positioning more accurate. While processing linear road data, we don't have to consider the relationship among real targets but refine the original linear vector layer and stored this layer and other linear layers separately. The latest version of ArcGIS supports the Feature Access, the ArcGIS API for Flex provides online editing tools to achieve the online map editing purposes. To reduce the size of the project, the real data on the server should be stored separately and the address link recorded and called when the application is running. In order to achieve better interaction with the digital campus, we adopted technology of RIA (Rich Internet Application) and built the digital campus system of Shandong University of Science and Technology based on ArcGIS Server and ArcGIS API for Flex. The system realized functions of geocoding address, querying, the shortest route analysis, online map editing and 360-degree virtual navigation. In this paper we focused on the key technologies on data arrangement, generation of 360-degree data and programming of the project. The successful experiments show that the precise geographical positioning network method, the separate management of the real data and online map editing are feasible.
As the amount of remote sensing data is sharply increasing within the continuing development in remote sensors, the exploitation of massive amount of remote sensing data is booming in recent years. Therefore, the computational problems in the applications that involve the large collection of remotely sensed imagery processing, such as global climate change and hazard assessment, arise inevitably. On this point, high performance computing (HPC)-based patterns, including cluster computing, grid computing, cloud computing and computing with hardware such as field-programmable gate arrays (FPGA) and graphic processing units (GPU), are introduced to the applications that concern a huge amount of remote sensing data processing. This paper focuses on the state of the art coping with the challenges that emerge when the massive remote sensing data are processed by the HPC-based platforms. In particular, we review recent developments in the parallel file systems for storing the remote sensing data and high performance geocomputation. Specifically, the HPC-based paradigms delivered in this paper involve cluster-based platform, grid and cloud based environments. Further, the typical examples of the HPC-based platforms that process the massive remote sensing data, comprising the Pixel Factory, the Grid Processing on Demand (G-POD) and the Geospatial Data Operation System-Image Processing Machine (gDos-IPM), are discussed. And the gDos-IPM, a solution for the platform of high performance computing for remote sensing, is described in detail. The gDos-IPM, which integrates the computation and storage resources and involves GPUs, multicore processors and clusters, provides the remote sensing tools about preprocessing and information extraction for massive remote sensing data in the heterogeneous computing environment. Also, it supports a dynamic model for spatio-temporal data and multi-level parallel computing. At the end of this paper, we present a thoughtful view on the challenges of HPC for further remote sensing applications.
Interferometric synthetic aperture radar (InSAR) phase unwrapping is one of the key technologies, which, uses the InSAR interference phase, to extract digital elevation model or accurate differential interferometry. However, affected by the porblem that the terrain is streep or the slope is larger, the unwrapping result is bad and causes error transmission in the differential wrapped phase information. In view of this problem, this paper considered to express the terrain slope in the interferogram as the partial phase frequency in range and azimuth direction. Using partial phase frequency to estimate the terrain slope and derivate the wrapped phase gradient probability density function (PG-PDF), the parameter model was used as the constraints of the nonlinear least squares phase unwrapping algorithm, in order to smooth the un-requirements unwrapped phase gradient. After unwrapping, the iterative solution which obtained from the results could eliminate the noise while reducing topographical factors under the condition of less sampling, at the same time the phase unwrapping results improved the accuracy of phase unwrapping. Finally, in the experiments that used the interferometric data obtained from ESA ENVISAT ASAR, it is verified that taking into account the terrain in the frequency domain method could effectively overcome the shortcomings of LS estimates for the phase gradient owed, and the algorithm in unwrapping could effectively give consideration to terrain factors, suppress error propagation, and have precision and adaptability to the terrain slope better than a direct weighted phase unwrapping algorithm.
In this paper we developed a PAR (photosynthetically active radiation) calculation system based on PARcalc algorithm which was driven by MODIS data. Before designing, we compared the characteristic of IDL with ArcGIS Engine, and analyzed the requirements of system functions. Therefore we designed a technical scheme which integrated IDL with ArcGIS Engine together, and chose C# as the main programming language. The communication between C# and IDL is dependent on the IDL ActiveX component. Then we gave a detailed introduction to the main modules and functions of the system and analyzed the key techniques for the implementation such as programming with C# and IDL in the same environment, data partition, batch computation of incident PAR, and batch computation of daily PAR by LM (Levenberg-Marquardt) algorithm. Finally we calculated the annual and seasonal PAR in Inner Mongolia in 2007 by the system, and made a statistic of the characteristic value. The results showed that the system provided a friendly man-machine interaction. It was easy to use and met the demands of practical applications. It had great reference value for PAR calculation in regional scale.
The spatial-temporal power-law distributions are found in many natural systems. In this paper, multi-temporal series of satellite GIMMS Normalized Difference of Vegetation Index (NDVI) data from 1982 to 2006 were exploited for studying long-range correlations in the Greater Khingan Mountains. We used Detrended Fluctuation Analysis (DFA), which permits the detection of persistent properties in nonstationary signal fluctuations. Firstly, anomaly NDVI fluctuations are the nonstationary signal and a complex driving system. Secondly, the first-order detrended fluctuation analysis is suitable for GIMMS NDVI datasets, and in NDVI fluctuations little time-scale won't be ignored. NDVI fluctuations are found to be persistent long-range power-law correlations, with exponent 0.85 (significance 99%), for time scales longer than 2 months and shorter than 15 months in the Greater Khingan Mountains. The DFA1 was applied to randomly shuffled versions of each of the original series. The exponent for the shuffled version of NDVI is about 0.5 (significance 99%). The result suggests that NDVI have self-similarity characteristics. Finally, the four fluctuation curves, calculated for the north, northwest, middle and south of the Greater Khingan Mountains present two scaling regions with crossover timescales at about 6.5 to 8.5 months. Break points of northwest and south came earlier than north and middle in the Greater Khingan Mountains. The first timescale regions are characterized by scaling exponents α1 varying from 0.93 to 1.17. It is shown that the interval sequences of NDVI closely resemble that of 1/f noise at a small timescale. The second scaling regions are featured by exponents α2 ranging between 0.61 and 0.84 and exhibit persistent long-range power-law correlations. North and middle correlations are stronger than northwest and south. Vegetation type and climate may affect the long-range correlation in some way. These findings could be proved useful in testing the results of climate-vegetation models.
