Table of Content

    20 March 2012, Volume 31 Issue 3 Previous Issue    Next Issue
    Earth Surface Processes
    Selection of major evaluation indicators on river health evaluation
    FENG Yan, HE Da-ming, YANG Li-ping
    2012, 31 (3):  389-398.  doi: 10.11821/yj2012030001
    Abstract ( 1216 )   PDF (457KB) ( 2064 )   Save
    River health has become one of hot topics on water issues in recent decades,and the corresponding evaluation index systems are becoming the objectives of river basin management in some countries and regions in the world.Most of the existing evaluation index systems on river health have not been widely used due to their complex and more professional indexes involved.The authors consider that some major evaluation/important indicators can be selected to show the status and developing tendency of river health.Around 150 research papers,documents and standards on river/river system health in 1972-2010 were reviewed,and 45 evaluation systems with 902 indicators were obtained.According to the river characteristics described in this study,the indicators were identified into four types: habitat physical index,water environmental index,biotic index and water utilization index.By the statistical method,the adopted number and the adopted rate for each indicator were calculated,and 26 indicators with higher adopted rate which can show the characteristics of river/river system from various aspects were selected as the candidates.Then,in order to make further selection of the more important,more universal,easily quantized and obtained ones from the above candidates,the methods of hierarchy analysis and correlation analysis of the indicators were used based on the conclusions of the relevant researches and the relevant concepts,and some of the candidates were incorporated into one if the means or characters of them were similar or overlapped or covered each other.Finally,8 indicators were determined as the major indicators for evaluating river health condition,which were: coverage rate of riparian vegetation,the changes of wetland extent,river continuity,the changing rate of water flow,the ratio of reaching water quality standard,fish index of biotic integrity,the ratio of water utilization and the coverage of natural vegetation in the watershed.
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    Effects of DEM resolution on results of the SWIM hydrological model in the Changtaiguan basin
    GAO Chao, JIN Gao-jie
    2012, 31 (3):  399-408.  doi: 10.11821/yj2012030002
    Abstract ( 1399 )   PDF (784KB) ( 31271 )   Save
    In this paper,the impacts of the Digital Elevation Model(DEM) with different resolutions on the simulation results of the SWIM hydrological model are examined for the Changtaiguan basin in the upper reaches of the Huaihe River basin in East China.Fifteen DEM resolutions(from resolution of 1000x1000 m to resolution of 30x30 m) are analyzed on their impacts on landscape parameters and runoff simulation results.Based on this,it is found that the best fitting DEM resolution in the study area is 90~120 m,and that both the ratio of Grid Area/Basin Area and the 'thousand million' formula are suitable methods.The Nash-Sutcliffe coefficients decline with DEM resolution;yet when DEM resolution is larger than 250 m,the Nash-Sutcliffe coefficients increase,because DEM grid is too coarse to display basin terrains.The simulation results of hydrological extreme events from 15 different DEM resolutions show a high variability.The high Nash-Sutcliffe coefficients do not reflect the hydrological extreme events,especially in the flood period.For the dry season,the simulation results of the 15 DEM resolutions show relatively good results.The results of the SWIM hydrological model are more sensitive to precipitation when the DEM resolution is decreasing.
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    Assessing the sensitivity of runoff to climate change in Naoli River watershed,Northeast China
    YAO Yun-long, WANG Lei, LU Xian-guo, YU Hong-xian
    2012, 31 (3):  409-416.  doi: 10.11821/yj2012030003
    Abstract ( 1283 )   PDF (625KB) ( 1535 )   Save
    Planning for potential future changes in water yield requires an understanding not only of possible climatic changes but also how a catchment hydrology might respond to such changes.Understanding catchment responsiveness,the sensitivity of catchment stream flow to changes in climatic conditions,was a useful method to examine the impacts of climate change on water resources in a watershed.In this paper,the artificial neural network(ANN) model of Naoli River watershed was constructed to assess the sensitivity of runoff to different climatic conditions.The model took the annual mean rainfall,annual minimum temperature and maximum temperature as the input parameters,and the annual mean runoff as the output parameter.The accuracy of the model was also assessed based on the statistical methods.According to the fourth reports of IPCC,we assumed nine climate change scenarios.Under the scenarios,the sensitivity of runoff to climatic condition was assessed.The results showed that: the constructed ANN model could better simulate runoff,and it could be used for sensitivity analysis of climate change;the runoff in the upper reaches of the watershed was more sensitive than that in the middle reaches,and the runoff was more sensitive to the rainfall than to the temperature.The artificial neural network(ANN) model is a simple method used to analyze the sensitivity of runoff to climatic conditions,but this method does not place emphasis on the spatial variation in runoff sensitivity.
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    Spatial and temporal distribution of inhalable particulate matters and the source tracing in the heating season of Beijing
    ZHAO Wen-hui, ZHAO Wen-ji, GONG Hui-li, GONG Zhao-ning
    2012, 31 (3):  417-428.  doi: 10.11821/yj2012030004
    Abstract ( 994 )   PDF (1413KB) ( 1890 )   Save
    Inhalable particulate matter(IPM) is one of the principal pollutants in Beijing.Sandy weather in spring and winter seasons results from regional airflow to a certain degree,in most cases from autochthonic pollution,especially in heating season of winter.This paper focused on the spatial and temporal distribution of IPM and the relationship between IPM and its influencing factors,combined with RS techniques as well as ground-based monitoring.It analyzed the change of underlying surface observed from high resolution remote sensing images in different periods.We collected the contents of particles with different diameters by ground observation instrument and analyzed their chemical composition.In addition,this paper studied the relationship of distribution of IPM and underlying surface using spatial analysis of GIS.The results indicate that the distribution of IPM pollution is closely related with underlying surface,man-made pollution sources,population density and meteorological conditions.
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    Measuring carbon dioxide emissions from energy consumption by tourism in Yangtze River Delta
    XIE Yuan-fang, ZHAO Yuan
    2012, 31 (3):  429-438.  doi: 10.11821/yj2012030005
    Abstract ( 1006 )   PDF (648KB) ( 1951 )   Save
    Climate change is projected to have great impact on tourism in various ways;however,tourism also contributes to climate change through the carbon dioxide emissions from transport,accommodation and other tourist activities.Now low-carbon tourism is becoming a popular choice to protect the environment for tourists.A lot of people have already accepted the low-carbon conception,and more and more people like it.But there are still numerous hurdles on the road to really achieve the low-carbon goal in our travels,because there is a large amount of direct energy consumption in the form of fossil fuels or indirect energy consumption in the form of electricity during the whole journey.And this consumption directly leads to more emissions of carbon dioxide.According to international experience,measuring carbon dioxide emissions from tourism is a key step to developing low-carbon tourism.However,the study of low-carbon tourism in China is still in its initial stage. Under the background of global energy conservation and emissions reduction,this paper builds up a rational method for measuring carbon dioxide emissions from tourism according to the situation of Chinese tourism.This measurement is based on a better understanding of the conception of low carbon,and it can strip tourist energy consumptions away from energy consumptions by related industries by using "tourist consuming minus coefficient".Taking the Yangtze River Delta as an example,we attempt to measure carbon dioxide emissions from tourism of Jiangsu and Zhejiang provinces as well as Shanghai,and then compare and analyze the results of measurement. The results are shown as follows.In the present stage,carbon dioxide emissions from tourism present an increasing trend.Moreover,there is a positive correlation between carbon dioxide emissions from tourism and the gross income of tourism in the Yangtze River Delta.It should be noticed that the main part in the total amount of carbon dioxide emissions from tourism is closely associated with transportation,storage industry,post,and telecommunication services.Besides,the carbon-dioxide emissions from tourism closely associated with dining,accommodation and shopping cannot be ignored.In general,there is considerable conflict between the increase of tourism income and the development of low-carbon tourism,hence the transformation of the development way of current tourism is urgently needed.
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    Dynamic calculation and analysis of sustainable development of Chizhou City in Anhui Province during 2001-2010
    ZHANG Le-qin, CHEN Su-ping, RONG Hui-fang, XU Xin-wang
    2012, 31 (3):  439-449.  doi: 10.11821/yj2012030006
    Abstract ( 1023 )   PDF (670KB) ( 1823 )   Save
    Chizhou is the first eco-economy demonstration area in Anhui Province.The rapid growth of national economy has aggravated the fragility and instability of the urban development in recent years,hence there are more chances and challenges for sustainable economic development.Based on analytical method of ecological footprint,we measured time sequence of ecological footprint and ecological capacity of Chizhou city from 2001 to 2010.Using GM,the eco-footprint per capita in 2015 and 2020 is predicted.The investigation shows that eco-footprint per capita of the city increased from 1.2458 hm2 to 2.2483 hm2,an annual rate of 11.14%,and the eco-deficit per capita increased from 0.8445 hm2 to 1.8266 hm2.The correlation coefficient between the consumption level of residents and eco-footprint per capita is about 0.844,and the correlation coefficient between the energy consumption and eco-footprint per capita is about 0.945,so the consumption level of residents and energy consumption are factors affecting eco-footprint.Energy ecological footprint has been increasing consecutively at an annual rate of 83.75%,which even surpassed the growth rates of biological footprint.Eco-footprint per ten thousand yuan GDP decreased from 2.98 hm2 in 2001 to 1.20 hm2 in 2010.This paper predicts that by the year 2015,the eco-footprint per capita will be 3.2336 hm2,and the ecological deficit per capita will be increased to 2.7926 hm2.By the year 2020,the eco-footprint per capita will be 4.4896 hm2,and the ecological deficit per capita will increase to 4.0308 hm2.Considering the unstable eco-situation in Chizhou,we propose several measures to reduce eco-footprint,including decreasing energy consumption,developing eco-tourism,changing people's consumption style,and raising crop yields.
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    Study on the longevity phenomena and human settlements in rural China: Taking Zhongxiang city as an example
    MA Jing-jing, ZENG Ju-xin
    2012, 31 (3):  450-460.  doi: 10.11821/yj2012030007
    Abstract ( 1062 )   PDF (579KB) ( 2149 )   Save
    Relationship between longevity phenomenon and human settlements in rural areas of China is an issue that geography and relevant disciplines focus on.Based on the multidisciplinary perspective of human geography,human settlement science,environmental science and rural community,the article illustrates the definition of longevity phenomenon in rural areas and analyzes the phenomenon of objective existence and its causes.Meanwhile,taking Zhongxiang city of Hubei Province as an example,this article comprehensively observes and studies the relationship between longevity phenomenon of rural China and the superior natural environment,harmonious social humanity environment and comfortable living condition.It examines five important aspects for reference,i.e.,the objective necessity of longevity phenomenon in rural areas,the comprehensiveness of the causes,the positive correlation between longevity and human settlements,the homogeneity of the longevity phenomenon between mountainous areas and plains and the immutability of a good health and a long life that human has been pursuing.Finally,this paper puts forward some suggestions in policy-making to build a rural human settlement which is conducive to a good health and a long life of residents.
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    Vegetation pattern changes and their influencing factors in the East Dongting Lake wetland
    LEI Xuan, YANG Bo, JIANG Wei-guo, YANG Yipeng, Claudia KUENZER, CHEN Qiang
    2012, 31 (3):  461-470.  doi: 10.11821/yj2012030008
    Abstract ( 1176 )   PDF (977KB) ( 2061 )   Save
    The bases for the protection of wetland vegetation cover and for the design of vegetation recovery initiatives is an available vegetation cover framework,including the variational characteristics and the investigation of factors influencing vegetation variability.In this paper,using Landsat TM/ETM+ data,we developed a decision framework for the extraction of wetland landscape information from three periods for East Dongting Lake.We then performed analyses of the changes of vegetation on the basis of transfer matrix and the centriods shifting method.Results are shown as follows.(1) From 1993~2002,the areas of forested land,reed land,and carex covered area increased,among them the reed land increased fastest,with an annual growth of 28.93 km2.During 2002~2006,forested land increased rapidly,with an annual growth of 29.655 km2,while the carex area decreased,and reeds remained unchanged.(2) The distribution of centroids of forest,reed and carex in the East Dongting Lake wetland layer by layer are close to the lake center,and entroids of these three vegetation types ceaselessly shifted to the lake centre from 1993 to 2006,among which,changes of forest and reed were more remarkable.
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    Mutual effects between morphological characteristics and variations of flow-sediment process of Dongting Lake during 1951~2009
    YIN Hui, YANG Bo, JIANG Zhong-cheng, ZENG Fa-ming, PENG Peng, LI Jing-bao
    2012, 31 (3):  471-483.  doi: 10.11821/yj2012030009
    Abstract ( 993 )   PDF (1090KB) ( 1919 )   Save
    Based on historical references,maps and flow-sediment data from 1951 to 2009,mutual effects between the lake morphology and the flow-sediment process of Dongting Lake were comparatively analyzed.The results showed that the lake morphology interacted with the flow-sediment process so that the lake morphology characteristics were changed by the flow-sediment process in several ways.For example,the structure of the lake basin was disaggregated and broken up,the lake became shallow,and the acreage and cubage of the lake decreased by 1840 km2 and 130×108 m3 respectively.Meanwhile,flow-sediment specialties were also changed by the alteration of lake morphology.The water storage of lake basin showed the obvious increase-decrease fluctuation from 1951 to 2002;however,the water levels under the same flux in main flood periods rose by 1.2 m to 1.9 m generally,and the water levels of west,south and east Dongting Lake increased by 1.61 m,1.39 m and 1.35 m respectively.When the top 5 flood levels of each main hydrological station and the smallest acreage or cubage of the lake appeared at the same time,the silting rate would be over 70%.Due to the Three Gorges Reservoir's water storage and Returning Farmland to Lake Project,the storage amount of the lake basin under the high and middle water levels slightly decreased.The high and low water levels of Chenglingji hydrological station decreased by 1.12 m and 0.35 m respectively.Sediment output ratios of west and southeast lake showed an increasing tendency.The silting rate reduced to 35.9%.The mutual effect mechanism could be summarized as the pattern: sediment siltation→the disaggregation and the break of lake basin structures as well as the decrease of the lake acreage and cubage→the change of flow-sediment specialties→the alteration of lake morphology→the change of flow-sediment specialties.
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    The minimum cost-cycle expansion law of urban spatial morphology: A case study of Kunming in China
    WU Qi-yan, CHEN Hui, Belinda WU, ZENG Wen
    2012, 31 (3):  484-794.  doi: 10.11821/yj2012030010
    Abstract ( 1255 )   PDF (959KB) ( 1302 )   Save
    The evolution of urban morphology is the changing pattern of urban land use.It is the external morphological outcome of the internal impetus of minimum cost on urban land use model.This paper argues that the process of morphology evolution is the result of alternant pattern of external expansion and internal infilling of land use in urban areas,which is the aufheben conducted by the interweaving behavior between concentration and dissimilation,as well as by the process of embedment and re-embedment of socio-economic action. Based on the above hypothesis,we select the(remote sensing) images of Kunming in temporal serial from 1909 to 2006,using morphological perspective to analyze the changes of urban spatial pattern and explore the evolution of urban morphology.The results are revealed that:(1) from the view of the rational micro-process and macro-process,in general,the evolution of urban morphology follows the pattern of the minimum cost-cyclic expansion in the statistics;(2) based on the minimum cost-cyclic expansion model,the core mechanism that drives the morphology of periodic changes is based on the impact between alternant pro-growth infrastructure investment and pro-consumption public investment infrastructure changes,as well as factor substitution effects in each spatial phase.
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    Study on the characteristics and territorial types of rural transformation development: The case of "Southern Jiangsu-Northern Shaanxi" transect
    LONG Hua-lou, ZOU Jian, LI Ting-ting, LIU Yan-sui
    2012, 31 (3):  495-506.  doi: 10.11821/yj2012030011
    Abstract ( 1203 )   PDF (929KB) ( 2040 )   Save
    Pushing forward rural transformation development is one of the key countermeasures to narrow the urban-rural development gap and to achieve the urban-rural coordination.This paper establishes the assessing indicator systems for studying rural transformation development,classifies the territorial types of rural transformation development in the "Southern Jiangsu-Northern Shaanxi" transect,and analyzes the characteristics of different types.The major conclusions are drawn as follows.(1) During 2000-2005,the characteristics of rural development of the counties in the transect show a universal low development level but a relatively high transformation level,which resulted in the uncoordinated development of urban and rural areas,but the situation was improved during 2005-2008.(2) The integrated assessing results of rural transformation development in "Southern Jiangsu-Northern Shaanxi" transect show strong relationship between the regional transformation characteristics and its own basic attributes,such as location,economic basis,development mode,and policy objective.(3) Based on the four regional attributes of geomorphological features,transformation characteristics,developing speed and urban-rural relationship,eight territorial type regions are divided in the "Southern Jiangsu-Northern Shaanxi" transect,and the research outcomes indicated that various location conditions and resources endowment among different regions contribute to the adoption of different modes of rural transformation development,which will result in the different changes in resources and environment system and urban-rural economic system.
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    Africa's position shift in world oil supply pattern
    HAO Li-sha, ZHAO Yuan
    2012, 31 (3):  507-520.  doi: 10.11821/yj2012030012
    Abstract ( 1134 )   PDF (1025KB) ( 1938 )   Save
    In the 21st century,Africa has been a strategic place for major oil importers seeking to diversify imports in order to achieve greater oil security,and also Africa has been the second biggest source for China,so that analyses of Africa's position shift in world oil supply pattern could help us to get a better understanding of Africa's advantages and disadvantages in the oil supply,in order to optimize China's strategy for oil cooperation with Africa.In this paper,boxplots and spatial cluster analysis are integrated,together with modified share and rank analysis,to examine and compare Africa's positions and their shift in the patterns of world oil proved reserves,oil production,reserves-to-production ratio,and exports.The results show that,Africa is the most concentrated area of oil supplying countries besides Middle East,and with the supersession of the old by the new,its overall supply position is relatively steady or even promoted;Africa's relative advantages in world oil supply pattern are its high reserves-to-production ratio and high export ratio,so that it is one of the key areas to provide sustained growth of oil production and export in the future;Africa has gradually penetrated the world's heartland of oil supply,and its oil geopolitical importance is enhanced greatly;in the long-term perspective,Africa will still be one of the major oil sources for China,and China should promote diverse strategies to Africa and enter Africa's core oil market,in order to enlarge supply,and achieve risk diversification.
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    Evaluation of the spatial coordinated development of Wulingshan Economic Cooperation Zone
    Leng Zhi-ming
    2012, 31 (3):  521-533.  doi: 10.11821/yj2012030013
    Abstract ( 955 )   PDF (916KB) ( 1542 )   Save
    The evaluation of the spatial coordinated development is one of the foci in research of regional economy,especially at the spatial coordinated development level.Different from viewpoints of previous studies,this paper believes that the essence of the spatial/regional coordinated development of regional economy is the economic links among countries/regions which have become ever stronger,regional gaps are gradually narrowing,and basic public services tend to convergent in the dynamic development process.According to the data related to 51 counties of six prefecture-level regions in Wulingshan Economic Cooperation Zone from the statistical yearbook during 2002-2010 and based on the concept of coordinated development to build spatial/regional evaluation system,this paper places emphasis on economic links,regional differences,dynamic convergence and sustainable development.In this paper,the four indexes which refer to comprehensive indexes are difficult to measure its relative importance directly,and the method which highlights the differences in the average local variance will result in unreasonable weight selection because the variance of each index of the four is unstable.Therefore,this paper takes the AHP judgment matrix as a subjective weighting method.Although this method,to some extent,is subjective,the weight based on rational thinking and analysis of experience can reflect the relationship between the intrinsic and relative importance.At the same time,to avoid the subjective factors,the author has consulted 20 experts from different fields and tests the consistency of each judgment matrix,and then builds a spatial/regional evaluation system from the equalization level of basic public services,the integration level of different regions,the equalization level of per capita GDP among different regions and the difference between consumption levels of urban and rural residents.The results show that from 2001 to 2009,the level of spatial coordination presents a rising trend and this can be explained by the enhancement of spatial coordination ability of Wulingshan Economic Cooperation Zone.But the spatial coordination level is not synchronous because there are huge differences in the equalization level of basic public services,the integration level of different regions,the equalization level of GDP among different regions and huge differences between urban and rural consumption levels in different parts of Wulingshan Economic Cooperation Zone.Based on this,the author tries to find the main restraining factors of economic development in Wulingshan Economic Cooperation Zone through the evaluation of the spatial coordination in the zone and provides a theoretical basis for implementing regional economic development strategy.
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    Analysis of industrial agglomeration and diffusion with spatial econometrics for six provinces in Central China
    SONG Ma-lin, WANG Shu-hong, HUANG Bei, HU Bai-hong
    2012, 31 (3):  534-542.  doi: 10.11821/yj2012030014
    Abstract ( 1186 )   PDF (552KB) ( 17229 )   Save
    With the strategy of "The Rise of Central China",the six provinces in Central China are offered golden opportunities for their great development.Accordingly,during the period of the 12th Five-Year Plan(2011-2015),it is vital for them to sum up experience of precedent development concerning adjusting and upgrading industrial structure,master the law of industrial updates,and reduce the unfavorable factors in economic development to a minimum,based on which sustainable development of regional economy by leaps and bounds can be realized.First,data of the secondary industry in the period of 2000-2008 for 88 prefectures and cities in Central China are collected and LISA is used to analyze spatial aggregation and diffusion,the result of which in combination with Moran's I and Geary's C methods provides a comprehensive assessment for the industrial development in the 88 prefectures and cities.Then integrated with Markov chain simulation,the probabilities of transferring among various states are calculated to predict industrial development in the future.Finally,the empirical results indicate that,with 10 years of rapid development,the secondary industry of the six provinces will reach the level of relative equilibrium on the condition that there will be no significant change in the environment inside and outside the whole region.
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    Investigating influencing factors of tourism consumption coupon effect based on structural equation model approach:A case study of Hangzhou
    WANG Xia, WU Xiao-gen, ZHANG Jin-he, Ren Li-xiu, LIU Ze-hua, ZHANG Hong
    2012, 31 (3):  543-554.  doi: 10.11821/yj2012030015
    Abstract ( 1284 )   PDF (694KB) ( 2279 )   Save
    Tourism consumption coupon is effective to promote consumption and stimulate economy.However,it also has limitations in launch place,launch unit,launch channel,launch object,use area,face value design,and use restriction,which confines the better effect of it.Employing structural equation model approach,this paper built the model of tourism consumption coupon effect and investigated key factors affecting tourism consumption coupon effect.The result are shown as follows.(1) Economic value,use inclination,use restriction,use reliability and draw convenience were five key factors affecting tourism consumption coupon effect.(2) Among the five influencing factors,economic value had the strongest impact on tourism consumption coupon effect,followed by use inclination,use reliability,draw convenience,and use restriction.(3) Economic value,use inclination,use reliability and draw convenience were positively related with tourism consumption coupon effect.They were four driving factors for promoting tourism consumption coupon effect.(4) Use restriction was negatively related with tourism consumption coupon effect,which showed a passive influence on tourism consumption coupon effect.
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    The multiagent-based-model method in analyzing the conservation behavior strategies of tourism destination
    FU Li-hua, XIE Bing-geng, LI Xiao-qing, ZHU Dong-guo, HU Xian-hui
    2012, 31 (3):  555-564.  doi: 10.11821/yj2012030016
    Abstract ( 873 )   PDF (455KB) ( 1505 )   Save
    A case study was selected in Liye,a historical and cultural town located in the west of Hunan.The theory of Complex Adaptive System was used in building the study system of the stakeholders expressing characters of different agents with protective behaviors.By using the method of agent-based model,five different agents were selected in analyzing the preference and influence of the system from a micro-level perspective,and protective behaviors diversity in a system was also analyzed in different development processes with a tourism destination.Based on the dynamic simulation with the outputs of multi-agents system,each agent expresses its own characters with the protective behavior.According to the results of agent-based model proposed in different stages with the model,how to choose and optimize the protective behavior,and how to coordinate the behavior of each agent in a system prospective were proposed,and the protective behavior strategies were also proposed.The results are obtained as follows.Firstly,the decision-making behavior expresses significant differences,and local residents play a leading role in the town's conservation.Secondly,the agent's behavior choices are characterized by autonomy,purpose and moderation.Thirdly,a hierarchical and classification coordination system of conservation behaviors should be established.Fourthly,the decision-making conservation behaviors of every agent and the system should be intervened dynamically.
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    A real-time visualization method for large 3-D vegetation scenes
    HAN Xiu-zhen, TAN Ji-qiang
    2012, 31 (3):  565-577.  doi: 10.11821/yj2012030017
    Abstract ( 976 )   PDF (1058KB) ( 1571 )   Save
    This paper addresses an approach for dynamic and continuous multi-resolution visualization of large forests.Firstly,the approach uses the L-systems to generate 3D tree models,which are composed of two kinds of geometric elements: branches and leaves.The plants are simplified respectively to multi-resolution models of branches and foliage by our method.Secondly,the approach quantifies the resolution of LOD models by the length of branches and the quantity of foliage.The branch length for the branch LOD model and the leaf quantity for the foliage LOD model are obtained by the decay factor.Taking the values as the criterion,we extract LOD models from the multi-resolution models of branches and foliage in real time.Finally,we render the forest scene.This paper presents a continuous LOD rendering for forest landscape,and the main originalities of our method are summarized as follows.(1) To improve the efficiency for extracting the continuous LOD models,the multi-resolution chains and the binary tree structures are established respectively for the branches and the crowns,both of which consist of the preliminary models of the tree.(2) Our method for generating crown LOD models here shows that,they can implement large forest scene real-time visualization.(3) This paper makes new criteria for the LOD models,which use the decay factor to act on the original branch length and the original leaf quantity.In this way,the levels for displaying trunk and branches are calculated.This method is applicable to all kinds of plants with strong universality and practicability.So how to simplify crowns of such kind of trees is another important research subject.In future work,we should combine geometry-based and image-based simplification methods to further speed up visualization of large plant scenes.
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