In the modeling process of Virtual Geographic Environment (VGE), as the geological objects generally have characteristics such as complex boundary, many spatial feature constraints including point, line, face and inside hole type, and meanwhile geosciences analysis and calculation require meshes with high quality, it is hard to construct three-dimensional meshes which regard for complex spatial feature constraints of geological objects exactly and have high quality for geosciences analysis and calculation. Aiming at this problem, a constrained Delaunay discrete algorithm of tetrahedral mesh is put forward in this paper. This algorithm first expresses constrained features of complex geological objects as a series of constraint points, constraint segments and constraint faces in Piecewise Linear Complexes (PLC), and then implements the initial Delaunay tetrahedral subdivision from the initial point set of the geological objects Piecewise Linear Complexes by using the Bowyer-Watson algorithm. Following the upper steps, the algorithm recovers the lost constraint lines and the lost constraint faces in sequence through adding some extra vertices during the mesh discrete process and it should guarantee the adding vertices do not encroach other constraint lines or constraint faces. The constraint face recovery is after the constraint line recovery and it is more difficult and complex than the constraint line recovery. In this step, some local meshes are demanded to reconstruct and must conform to the Delaunay empty circumsphere criterion. And then, the object model external tetrahedron elements should be deleted by adopting a marking method. After this step, it performs the mesh quality control process by restricting the maximum radius-distance ratio or the volume of tetrahedron element in the mesh. In this step, some extra vertices are also added in the tetrahedron elements which can not satisfy the user restricting quality. It is proved that the algorithm can produce meshes not only satisfying different constrained criteria but also with high quality for geosciences analysis and calculation.
Mountain basal elevation (MBE) is the elevation of the base which mountains uplift from. The variation of MBE affects the redistribution of water and heat conditions in mountain areas, and the structure and distribution of mountain altitudinal belts. But so far, there has been no accurate and scientific concept of MBE and no effective method to quantitatively extract it. This paper discusses the features of MBE, and develops a new quantitative method for MBE extraction based on topographical features. There are several algorithms available for automated extraction of topographical features, including ridge line, valley line and the boundary of mountains, and most of the current approaches are mainly based on regular statistic unit. This paper takes Taiwan mountain areas for experimental zone, and uses ASTER GDEM at resolution of 30m. Firstly, extracting main ridge line and main valley line by terrain analysis and hydrological analysis, and using topographical features to extract the boundary of mountains. Then based on the result of extraction, the distribution and the value of MBE are determined. The results show that the mountain areas of Taiwan can be divided into six MBE areas (0m, 150m, 200m, 600m, 630m, and 650m). The results can represent the distribution of Taiwan mountain basal elevation. This MBE extracting method is based on sophisticated algorithms, so it can improve the efficiency of the extraction process and the accuracy of results. The method could promote the extraction of the world's mountain basal elevation and the quantitative research of mass elevation effect.
Energy fixation and organic matter production of forest ecosystem were dominated by plants, which are impacted by their growth environment. The forest ecosystem has the characteristic of long life-span, which makes its research laborious and costly using field experiment. The virtual geographical environment can provide a new way for its research due to its character of trying to exceed the limit of time and space. In order to estimate the biomass and evaluate relationships among tree and environments, an L-systems based functional-structural model was developed for simulating the development of tree architecture, taking into account tree physiology and environment. The L-systems was used to represent the morphological development of tree. The basic growth unit was described in line with the development of young Chinese fir (Cunninghamia lanceolata). LSTree system integrated the photosynthesis, photosynthates allocation and morphogenesis models. The spatial distribution of solar radiation in tree canopy was simulated for calculating photosynthetically active radiation (PAR) of each leaf obtained. PAR is a key parameter for photosynthesis model to estimate biomass. The dynamic growth of an individual 3-to-4-year-old Chinese fir in Fuzhou was simulated in growing season. Based on the 2010 Fuzhou weather and Chinese fir photosynthetic characteristic, net photosynthesis rate and product were calculated for each stage. The amount of photosynthates allocated to the growth of new segments and leaves or branches and leave amplification are based on source-sink theory. The growth of tree is driven by available photosynthetic products after respiration losses were accounted for. The morphogenesis change in the young Chinese fir in response to environment was simulated dynamically in three dimensional representations. The result of net photosynthesis was compared to the previous field observation research, and it showed the simulation result was reasonable. The methodology has promising benefits to depicting the interaction of plant and environment, which will be valuable for estimation of organic matter production too.
Landscape perception plays a basic role in the planning of tourist destination. But there has not been research methods appeared at the micro-scale so far. This paper presents an abstract method for feature point based on the classification of landscape perception. And a calculation model of the semantic meaning perception degree about both single and multiple cultural landscapes is established to solve the perception problems occurred inside the humanistic tourist destination. An empirical research of semantic meaning perception of landscape was realized in the study of The Western Tombs of the Qing dynasty by using the DEM. According to traditional Chinese culture, this paper extracted 78 feature points from different landscape perspectives in 4 representative mausoleums which were given corresponding weights to figure out the perception degrees of the points. And based on the mining of the meaning of the landscapes in the sightseeing route, the viewpoints were designed. It offered a research approach to the quantitative description of landscape perception and method reference to the planning of tourist destination, the design and improvement of landscapes and sightseeing routes. By adopting the thoughts of cartographic generalization and the abstract method of feature point for landscape meaning, this paper established a virtual sight of tourist destination based on DEM and high quality data source to study the cultural landscape meaning perception. The result of this paper provides a foundation of quantitative evaluation of selection of the best sightseeing point of single and multiple cultural landscapes, and it means greatly as a reference in the study of inside cultural landscape of humanistic tourist destination of geo-science. It gives the tourist guides the best places for their explanations and a feasible method for transferring the cultural connotation of humanistic tourist destination to the tourists complementally and abundantly.
At present, semantic heterogeneity still presents challenges for geo-data integration in the open and distributed environment. Existing semantic heterogeneity resolving approaches enable semantic interoperability mostly through superficial semantic annotation of data such as using simple synonyms mapping between fields of different data schema, whereas hardly thinking of semantic data organization from bottom. They not only involve too many complex and trivial procedures for the user, but also require that the user should have enough knowledge. What is worse is that they can not solve problems once for all and not easy to use either. Consequently in this paper, we focus on semantic heterogeneity in geo-data source in open and distributed environment. We present an approach of ontology-based web geo-data integration that contributes to solving problems caused by semantic heterogeneity and hides most of the complexity of required procedures from the user. It reconciles such semantic conflicts by adopting the emerging semantic web technologies. On the basis of ontology-based semantic data organization and Open Geospatial Consortium's (OGC) Web Feature Service (WFS) publishing mechanism, a hybrid ontology approach is used to provide a global unified view. It acts as a semantic mediator among data sets that of each local application level ontologies and makes them interoperable via the global view. In this way, details involved in query mapping, data retrieval and data conversion are hidden and an intelligent retrieval and integration mechanism is provided for user. Its applicability and advantages are illustrated through a prototype application in a coastal land use scenario.
Global and China's Surrounding Regional Resources and Environmental Science Database is the basic support data for the resources and environmental leading scientific researches such as global change and for national macro decisions, which has vital significance for national security. From the key deployment project "Construction and Decision Supporting Research of the Global and Neighboring Countries' Resources and Environmental Science Database" of the Chinese Academy of Sciences, we have constructed the global and surrounding area resources and environmental science database framework, which includes three big system: Standards System Structure of the Resources and Environmental Science Database, Global Resources and Environmental Science Database and Surrounding Regional Resources and Environmental Science Database. The Standards System Structure of the Resources and Environmental Science Database includes three types combined with 22 standards; the Global Resources and Environmental Science Database and Surrounding Regional Resources includes two categories, 13 classes and 35 small types of database; the Surrounding Regional Resources and Environmental Science Database consists of four areas, i.e. northeast Asia, southeast Asia, South Asia and central Asia, which are up to 23 small kinds of database and aim at providing reference to the next work on the construction of large scale resources and environmental science database. And the work of the construction of the Global and China's Surrounding Regional Resources and Environmental Science Database will be better perfected by the "further" and "expanding" aspects in the future.
Compared with statistical downscaling methods and dynamical downscaling methods, HASM-based downscaling methods, which do not need large-scale predictor, can directly create high-resolution climatic surfaces under GCM scenarios. HASM downscaling methods separate future climate elements into climate base value and prospect climatic change value. This method is termed HASM-Constant Coefficient Downscaling Model (HASM-CDM) because climatic base value is fitted by global constant regression model and climatic change value is interpolated by HASM. Although HASM can obtain higher accuracy than other classical methods, precipitation base value fitted by (HASM-CDM) lost spatial non-stationary features of precipitation, which decreases the accuracy of precipitation simulation. The relationship between precipitation and auxiliary variables such as DEM and some topographical factors may change according to geographical location which can not be represented by HASM-CDM. HASM-Spatially Variable Coefficient Downscaling Model (HASM-SVDM) was developed which integrated with spatially variable coefficient regression model and data transformation in this paper. HASM-SVDM uses variable coefficient regression and data transformation to solve accuracy problem of climatic base value. The mean annual temperature (MAT) and mean annual precipitation (MAP) are constructed under different scenarios of HadCM3 A1Fi, A2a and B2a during the periods T1 (1961-1990), T2 (2010-2039), T3 (2040-2069) and T4 (2070-2099) by HASM downscaling models. The results show that HASM-constant coefficient downscaling model integrated with global linear model is applicable to the temperature downscaling simulation, while HASM-spatially variable coefficient downscaling model improves spatial non-stationary base value, and is appropriate for the precipitation downscaling modeling at the national level.
Tropical cyclones (TCs) over the Northwest Pacific play an important role on climate change. Based on the Yearbook of Tropical Cyclones during the period of 1981-2010 and the developer kit of ArcEngine 9.3, this paper analyses the TCs' time characteristics and space characteristics and spatio-temporal characteristics. We have constructed a typhoon disaster geographic information system, which includes typhoon information point database and line database. The function of the database includes: login interface, map search attribute, property search map, database analysis and processing function. Our main conclusions are as follows: firstly, the Northwest Pacific typhoon occurred 905 times and average 30.2 times per year. The typhoons mainly occurred during the period from July to October that covered a proportion of 35.7%. The frequency of typhoons in August reached the peak and covered the ratio of 21.5%. February is the most difficult month of typhoon and the occurrence frequency is only 0.6%. Powerful typhoon and super typhoon mainly focused on August to October. Secondly, the birthplace of typhoon showed a characteristic of with latitude and longitude band, mainly distributed over regions of (10°~22°N, 112°~120°E), (8°~20°N, 126°~134°E) and (6°~20°N, 136°~150°E). Thirdly, the birthplaces of typhoon presented significant seasonal variation. In summer, typhoon distributed over north and west area, then gradually shifted south and east until to north and west in winter. Typhoon birthplace showed significant monthly variation that scattered in January-April, shifted to north and west from May to June, spread north and east in July, was westward in August-September and southward in October. In September, the sources were relatively concentrated. In November-December, typhoon sources significantly reduced.
We quantitatively analyzed the space heterogeneity of land use degree in the Jiuxiang River watershed. This is of great significance to land consolidation and sustainable use of land resources in the urbanized watershed. Jiuxiang River watershed in Nanjing City, as a case study area, its two landscape classification maps were conducted from 2003 and 2009 by remote sensing images interpretation, which were used as the main data source for assessment of land use degree. Spatial heterogeneity characteristics of land use degree in the study area were analyzed during 2003-009 by means of spatial statistics like spatial autocorrelation and semi-variance analysis. The results showed that with the increase of spatial distance, the spatial correlation of land use degree showed a downward trend in Jiuxiang River basin. The high value area of land use degree was mainly located in the northwest Xianlin College Town and Shibu Bridge area, and the low value area mainly gathered in the northern Qinglongshan Mountain, the central Linshan Mountain and the northern West Lake Park area. Land use degree was mainly at the level of moderate in Jiuxiang River Basin from 2003 to 2009, accounting for about 40% of the watershed area. Affected by the urbanization process, the spatial heterogeneity of land use degree changed obviously, and the watershed land use degree showed the trend of conversion to stronger and weaker, the distribution area had an increase of 1.13% and 4.27%, respectively in six years. The land use degree in Xianlin College Town area enhanced, showed a trend of rapid expansion, but the land use degree slightly decreased in Jiuxiang River headwater, along the downstream coast and the West Lake Park. So we should establish a watershed ecological planning or land use planning to reduce the land use degree by controlling the density of building lands strictly, protecting forestlands, and enhancing the landscape construction.
Based on GIS, we analyzed the urban land use change of Chongqing main city zone from 1986 to 2007, and evaluated the urban land use degrees, land use diversity and the transfer of urban land use cores. At last, we analyzed the driving factor of the urban land use from population and elevation. The results showed: (1) the cultivated land and the wood land were more than the other land types, showing a low ratio of urban landscape. From 2000 to 2007, it had the fastest speed of the land variation, the cultivated land increased firstly and then decreased, the wood land decreased firstly and then increased, the water body, construction land and grass land were kept increasing. (2) The result of land transfer corresponded to human activities in some degrees, i.e. from 1986 to 1995, there were some agricultural activities (damage of wood land and grass land for cultivated land), and the urban expansion was very slow; from 1995 to 2000, these destroy activities were reduced, and the urban expansion was speeded up; from 2000 to 2007, urban expansion was very rapid. At the same time, there were some complex disturbances by humans: the urbanization was intense, the Three Gorges Project affected regional land impoundment obviously, and some lower lands were submerged. The effect of "Green for Grain" is remarkable. (3) From 1986 to 2007, the shift of cultivated land core and wood land core was opposite and the two cores were closely related. The core of future urban construction land would be in the "New District along the Two Rivers" in the north of the city. The degree of urban land use will increase gradually, especially in the northern part. The diversification of land use types increased gradually, too, with a pattern of lower in the east and higher in the west, and it was strongly impacted by the construction land changes. (4) The population and the altitude are closely related to the urban land use change. Urban population increased sharply, leading to the diversification in the degree and structure of urban land use. In the main city zone of Chongqing, topography is the primary impact factor. Construction land was located in the lower belts and plain regions, making a scattered distribution of urban cores which is different from Beijing, Shanghai and other big cities.
Camera self-calibration is a key step to acquisition 3D space information from 2D image, and it is always one of the important issues in photogrammetry. However, present methods for camera self-calibration need two or more images and/or their corresponding points. With the development of digital devices for image taken and (wireless) network, a method not depending on digital device, images taken process, or multiple images, is badly needed. Consequently this paper presented a novel method that makes full use of various geometric constraints to realize reliable camera calibration for a single image. Firstly, this paper summarized various geometric constraints and invariants for the existing camera self-calibration method. Secondly, in order to build the relationships among geometric constraints for calibration, we coded for different planes and geometric features in an image. Because variance represents the error distribution, it can be considered as the determinant. In this paper, we obtained the variance of different combination of geometric features for camera calibration by means of fitting each groups of geometric features for thirty times, and then depended on the variance above to determine the weight of each camera's internal parameters. Finally, based on each camera's internal parameters, here we only focus on foci length, and their corresponding weights, the ultimate results are computed. Two images which depict inside and outside scene respectively were chosen to test the usability of our methods. In order to avoid the influence of image distortion, we corrected it using amethod we proposed in another paper before tests. The test results show that: 1) the weighted method gave a more stable result, relative to the result of each group geometric constraints, that is one group's relative error is two high and in other may be lower; 2) the weighted method obtained a higher accuracy result than the mean of all groups. The results of verification testing for the two images of the indicated that our weighted method can comprehensive employs variety of geometric constraints in single image, in the other side, it also takes their corresponding variance into account. It makes full use of the variety, usability and stability of geometric constraints. It can be employed to images depict indoor and outdoor which contains more geometric constraints.
The water held in the top few centimeters of the soil is a key variable in many hydrological, climatological and ecological processes. These data are difficult and costly to acquire through in situ measurements, especially at high temporal frequencies. Different types of remote sensing systems are currently used to infer soil moisture at different spatial and temporal scales, each with its specific characteristics and limitations. The soil moisture retrieval from passive microwave is not affected by the weather, and the algorithm is mature and reliable. But the spatial resolution of spaceborne passive microwave data is too low for many local applications, and the data are suitable for large scale studies. Optical sensors complemented with thermal infrared channels have, in spite of the strong atmospheric attenuation and the limited penetration depth of the used signal, received much attention as a source of information on soil moisture content and surface evaporation. The way the high spatial resolution surface evaporation information contained in optical/thermal sensors can be combined with relatively low resolution soil moisture. Selecting 1km resolution the Moderate Resolution Imaging Spectroradiometer (MODIS) optical data and 25km resolution the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) passive microwave data 2 level of soil moisture product, the authors used NDVI-Ts feature space to remove the vegetation effect, and decompose the passive microwave soil moisture through a soil evaporation model. At last the authors got the 1km resolution soil moisture. Through building scatter diagram, it could be found that the relevance between the inversion result and 1km Temperature Vegetation Drought Index (TVDI) reached 0.569. The quantitative results of the study still need further validation and improvement.
Land surface component temperature has more significant physical meaning, and it reflects the actual distribution of temperature more significantly. Meanwhile, its retrieval algorithms have no need for hypothesis that components in pixels have the same temperature. Although the multi-angle retrieval algorithm of component temperature has become mature gradually, its application in the studies on urban thermal environment is restricted due to the difficulty in acquiring urban-scale multi-angle thermal infrared data. Therefore, based on the existing multi-band remote sensing data, access to appropriate urban-scale component temperature is an urgent issue to be solved in current studies on urban thermal infrared remote sensing. In this paper, a new algorithm to retrieve land surface component temperature for urban area had been proposed. It took advantage of ASTER data, and evaluated mean emissivity of pixels based on linear spectral unmixing, retrieved atmospheric water vapor content from MODIS NIR bands, and used Newton's iterative method to obtain atmosphere average temperature. Finally, an experimental study of this algorithm had been conducted and the retrieval result had been validated using some measured data. The results showed that: (1) the results of component temperature retrieval algorithm and split window algorithm of pure pixels have high correlation coefficient and the correlation coefficient of vegetation is the highest; (2) compared with the measured data, biases of the retrieval result ranged between 0.2 and 1.4℃, and the vegetation component temperature among different components had the smallest bias value.
Wenchuan Earthquake caused great damage to the ecological environment in the disaster-stricken area. In order to know the current recovery of the ecological environment damaged by the earthquake and provide data support for relevant researchers and decision makers, this paper took Landsat TM remote sensing images of June or July during 2006, 2008 and 2011 of Wenchuan earthquake disaster-stricken area as data sources, used computerized and artificial visual interpretation method to extract the land uses information of the study area, and combined topographic factors such as elevation and slope to comprehensively analyze the reasons of the change of major ecosystems (farmland, forest and grassland). The results showed that the earthquake damaged the ecosystem of the study area seriously, resulting in substantial shrinking of farmland, forest and grassland by 124.6km2, 461.6km2 and 92.3km2 respectively in the study area, and the farmland ecosystem had the most serious loss in Beichuan, Qingchuan and Pingwu counties, while the forest ecosystem lost 285.5km2 in Wenchuan County. The degree of influence on each ecosystem also varies a lot according to different altitudes and slopes. Up to the 2011, the status of the damaged ecosystem had got better in the study area through natural succession and artificial restoration intervention. Farmland, forest and grassland ecosystems had experienced certain degree of recovery, their areas increased 82.8km2, 58.3km2 and 174.9km2 respectively. The recovery of farmland and forest ecosystems is not satisfactory while the area of grassland ecosystem had got the most increase, in 2011 which had exceeded the reduced area damaged by the earthquake in 2008, whereas the whole recovery of the ecosystems in research area was not ideal. Further measures of ecological recovery are thus in dire need of.
