Tens of thousands of landslides were triggered by May 12, 2008 earthquake over a broad area. The main purpose of this article is to apply and verify earthquake-triggered landslide hazard analysis techniques by using w...Tens of thousands of landslides were triggered by May 12, 2008 earthquake over a broad area. The main purpose of this article is to apply and verify earthquake-triggered landslide hazard analysis techniques by using weight of evidence modeling in Qingshui （清水） River watershed, Deyang （德阳） City, Sichuan （四川） Province, China. Two thousand three hundred and twenty-one landslides were interpreted in the study area from aerial photographs and multi-source remote sensing imageries post-earthquake, verified by field surveys. The landslide inventory in the study area was established. A spatial database, including landslides and associated controlling parameters that may have influence on the occurrence of landslides, was constructed from topographic maps, geological maps, and enhanced thematic mapper （ETM＋） remote sensing imageries. The factors that influence landslide occurrence,such as slope angle, aspect, curvature, elevation, flow accumulation, distance from drainages, and distance from roads were calculated from the topographic maps. Lithology, distance from seismogenic fault, distance from all faults, and distance from stratigraphic boundaries were derived from the geological maps. Normalized difference vegetation index （NDV1） was extracted from ETM＋ images. Seismic intensity zoning was collected from Wenchuan （汶川） Ms8.0 Earthquake Intensity Distribution Map published by the China Earthquake Administration.Landslide hazard indices were calculated using the weight of evidence model, and landslide hazard maps were calculated from using different controlling parameters cases. The hazard map was compared with known landslide locations and verified. The success accuracy percentage of using all 13 controlling parameters was 71.82%. The resulting landslide hazard map showed five classes of landslide hazard, i.e., very high, high, moderate, low, and very low. The validation results showed satisfactory agreement between the hazard map and the existing landslides distribution data.展开更多
The coronavirus disease 2019(COVID-19)and its mutant viruses are still wreaking global havoc over the last two years,but the impact of human activity on the transmission of the pandemic is difficult to ascertain.Estim...The coronavirus disease 2019(COVID-19)and its mutant viruses are still wreaking global havoc over the last two years,but the impact of human activity on the transmission of the pandemic is difficult to ascertain.Estimating human dynamic spatiotemporal distribution can help in our understanding of how to mitigate COVID-19 spread,which can help in maintaining urban health within a county and between counties within a country.This distribution can be computed using the Volunteered Geographic Information(VGI)of the citizens in conjunction with other variables,such as climatic conditions,and used to analyze how human’s daily density distribution quantitatively affects COVID-19 transmission.Based on the estimated population density,when the population density increases daily by 1 person/km^(2) in a county or prefectural-level administrative unit with an average size of 26,000 km^(2),the county would have an additional 3.6 confirmed cases and 0.054 death cases after 5 days,which is the illness onset time for a new COVID-19 case.After 14 days,which is the maximum incubation period of the COVID-19 virus,there would be 5 new confirmed cases and 0.092 death cases.However,in neighboring regions,there can be 0.96 fewer people infected with COVID-19 on average per day as a result of strong intervention of local and neighboring authorities.The primary innovation and contribution are that this is the first quantitative assessment of the impacts of dynamic population density on the COVID-19 pandemic.Additionally,the direct and indirect effects of the impact are estimated using spatial panel models.The models that control the unobserved factors improve the reliability of the estimation,as validated by random experiments and the use of the Baidu migration dataset.展开更多
According to many previous studies,application of remote sensing for the complex and heterogeneous urban environments in Sub-Saharan African countries is challenging due to the spectral confusion among features caused...According to many previous studies,application of remote sensing for the complex and heterogeneous urban environments in Sub-Saharan African countries is challenging due to the spectral confusion among features caused by diversity of construction materials.Resorting to classification based on spectral indices that are expected to better highlight features of interest and to be prone to unsupervised classification,this study aims(1)to evaluate the effectiveness of index-based classification for Land Use Land Cover(LULC)using an unsupervised machine learning algorithm Product Quantized K-means(PQk-means);and(2)to monitor the urban expansion of Luanda,the capital city of Angola in a Logistic Regression Model(LRM).Comparison with state-of-the-art algorithms shows that unsupervised classification by means of spectral indices is effective for the study area and can be used for further studies.The built-up area of Luanda has increased from 94.5 km2 in 2000 to 198.3 km2 in 2008 and to 468.4 km2 in 2018,mainly driven by the proximity to the already established residential areas and to the main roads as confirmed by the logistic regression analysis.The generated probability maps show high probability of urban growth in the areas where government had defined housing programs.展开更多
Spatio-temporal patterns of flowering in forest ecosystems are hard to quantify and monitor. The objectives of this study were to investigate spatio-temporal patterns（e.g. soilssimple slope classesslope aspectand flo...Spatio-temporal patterns of flowering in forest ecosystems are hard to quantify and monitor. The objectives of this study were to investigate spatio-temporal patterns（e.g. soilssimple slope classesslope aspectand flow accumulation） of flowering around Lake IssaqueenaSouth Carolina（SCUSA） using plant-flowering database collected with GPS- enabled camera（stored in Picasa 3 web albums and project website） on a monthly basis in 2012 and Li DAR-based topography. Pacolet fine sandy loam had the most flowering plantsfollowed by Madison sandy loamboth dominant soil types around the lake. Most flowering plants were on moderately steep（17%–30%） and gently sloping（4%–8%） slopes. Most flowering plants were on west（247.5°–292.5°）southwest（202.5°–247.5°）and northwest（292.5°–337.5°） aspects. Most flowering plants were associated with minimum and maximum flows within the landscape. Chi-square tests indicated differences in the distributions of the proportions of flowering plants were significant by soil typeslopeaspectand flow accumulation for each month（February-November）for all months（overall）and across months. The Chi-square test on area-normalized data indicated significant differences for all months and individual differences by each month with some months not statistically significant. Cluster analysis on flowering counts for nine plant families with the most flowering counts indicated no unique separation by clusterbut implied that the majority of these families were flowering on strongly sloping（9%–16%） slopeson southwest（202.5°–247.5°） aspectsand low flow accumulation（0–200）. Presented methodology can serve as a template for future efforts to quantify spatio-temporal patterns of flowering and other phenological events.展开更多
Since the introduction of geographic information systems(GIS)in the 1960s,it has evolved tremendously to an extent that it permeates our daily lives.Initially,GIS usage started in the developed countries and now incre...Since the introduction of geographic information systems(GIS)in the 1960s,it has evolved tremendously to an extent that it permeates our daily lives.Initially,GIS usage started in the developed countries and now increasingly filtered to developing countries.The town planning profession was one of the early adopters of GIS.Geospatial information is a useful source of data that is needed in urban planning.In these days of the New Urban Agenda 2030,smart cities are even more required from planners in using geospatial information to face urban challenges such as sustainable urban development and climate change.Although GIS has promised a lot for urban planning,it has not reached its full potential.Moreover,many studies have focused on developed countries with limited studies on geospatial information application in municipalities and GIS education from a perspective of developing countries.In this study,a survey on the usage of geospatial information science(GSIS)in two cities,namely Bulawayo in Zimbabwe and Ekurhuleni in South Africa,was conducted,and an overview of the state of GIS curricula in planning schools is discussed.The results indicate that considerable progress has been made in the application of geospatial information in municipal planning;however,there are impediments limiting the full utilization of geospatial information in local municipalities.These impediments include:inadequate GIS curricula in planning schools,lack of resources,and lack of political will.These challenges manifest differently in well-resourced municipalities and those with limited resources.The study proposes planning-relevant GIS curricula to improve the level of GIS use in planning practice.展开更多
The aim of this study was to determine how well the landslide susceptibility parameters,obtained by data-dependent statistical models,matched with the parameters used in the literature.In order to achieve this goal,20...The aim of this study was to determine how well the landslide susceptibility parameters,obtained by data-dependent statistical models,matched with the parameters used in the literature.In order to achieve this goal,20 different environmental parameters were mapped in a well-studied landslide-prone area,the Asarsuyu catchment in northwest Turkey.A total of 4400 seed cells were generated from 47 different landslides and merged with different attributes of 20 different environmental causative variables into a database.In order to run a series of logistic regression models,different random landslide-free sample sets were produced and combined with seed cells.Different susceptibility maps were created with an average success rate of nearly 80%.The coherence among the models showed spatial correlations greater than 90%.Models converged in the parameter selection peculiarly,in that the same nine of 20 were chosen by different logistic regression models.Among these nine parameters,lithology,geological structure(distance/density),landcover-landuse,and slope angle were common parameters selected by both the regression models and literature.Accuracy assessment of the logistic models was assessed by absolute methods.All models were field checked with the landslides resulting from the 12 November 1999,Kaynas¸li Earthquake(Ms7.2).展开更多
Water depths and flow velocities decisively influence the damage caused by flash floods.Geographic Information System(GIS)is a powerful and useful tool,allowing the spatial analysis of results obtained by hydraulic mo...Water depths and flow velocities decisively influence the damage caused by flash floods.Geographic Information System(GIS)is a powerful and useful tool,allowing the spatial analysis of results obtained by hydraulic modelling,namely from the HEC-RAS/HEC-GeoRAS software.The GIS spatial analysis performed in this study seeks to explain and quantify the spatial relationships between the stream channel features and flow components during flash flood events.Despite these relationships are generically known,there are few studies exploring this subject in different geographic contexts.A 1D hydraulic model was applied in a small watershed in Portugal,providing good results in the definition of floodable areas,water depths and longitudinal velocities.No direct relationship was found between water depths and velocities in the floodable areas;however,negative strong correlations were found between the two flow components along the stream centerlines.Bed slope,channel and flood width,and roughness prove to be highly relevant on the longitudinal variations of water depths and velocities and on the location of maximum values.Increasing peak discharges and return periods(R;)can change the relationships between water depths and velocities at the same location.Results can be improved with more accurate elevation data for stream channels and floodplains.展开更多
Dispersal is one of the most important but least understood processes in plant ecology and evolutionary biology.Dispersal of seeds maintains and establishes populations,and pollen and seed dispersal are responsible fo...Dispersal is one of the most important but least understood processes in plant ecology and evolutionary biology.Dispersal of seeds maintains and establishes populations,and pollen and seed dispersal are responsible for gene flow within and among populations.Traditional views of dispersal and gene flow assume models that are governed solely by geographic distance and do not account for variation in dispersal vector behavior in response to heterogenous landscapes.Landscape genetics integrates population genetics with Geographic Information Systems(GIS)to evaluate the effects of landscape features on gene flow patterns(effective dispersal).Surprisingly,relatively few landscape genetic studies have been conducted on plants.Plants present advantages because their populations are stationary,allowing more reliable estimates of the effects of landscape features on effective dispersal rates.On the other hand,plant dispersal is intrinsically complex because it depends on the habitat preferences of the plant and its pollen and seed dispersal vectors.We discuss strategies to assess the separate contributions of pollen and seed movement to effective dispersal and to delineate the effects of plant habitat quality from those of landscape features that affect vector behavior.Preliminary analyses of seed dispersal for three species indicate that isolation by landscape resistance is a better predictor of the rates and patterns of dispersal than geographic distance.Rates of effective dispersal are lower in areas of high plant habitat quality,which may be due to the effects of the shape of the dispersal kernel or to movement behaviors of biotic vectors.Landscape genetic studies in plants have the potential to provide novel insights into the process of gene flow among populations and to improve our understanding of the behavior of biotic and abiotic dispersal vectors in response to heterogeneous landscapes.展开更多
Almost all causative factors of diseases depend on location.The Digital Earth approach is suitable for studying diseases globally.Geospatial information systems integrated with statistical models can be used to model ...Almost all causative factors of diseases depend on location.The Digital Earth approach is suitable for studying diseases globally.Geospatial information systems integrated with statistical models can be used to model the relationship between a disease and its causative factors.Through modelling,the most important causative factors can be extracted and the epidemiology of the disease can be observed.In this paper,skin cancer(the most common type of cancer)has been modelled based on its causative factors,including climate factors,people’s occupations,nutrition habits,socio-economic factors,and usage of chemical fertiliser.To fit the model,a data framework was first designed,and then data were gathered and processed.Finally,the disease was modelled using Generalised Linear Models(GLM),a statistical model based on the location of the factors.The results of this study identify the most important causative factors together with their relative priority.Furthermore,a model was used to predict the change in skin cancer occurrences caused by a change in one of its causative factors.This work illustrates the ability of the model to predict disease occurrence.Thus,by using this Digital Earth approach,skincancer can be studied in all the key countries around the world.展开更多
3D terrain visualization of geographic information systems(GIS)data has become an important issue in recent years.This is due to the emergence of new geo-browsers such as Google Earth,widely popular among users.The av...3D terrain visualization of geographic information systems(GIS)data has become an important issue in recent years.This is due to the emergence of new geo-browsers such as Google Earth,widely popular among users.The availability of 3D representation tools has increased the demand for 3D terrain visualization.The aim of this paper is to review the literature related to the 3D terrain visualization of GIS data from the first map produced until the online mapping era.The reviews are divided into four different sections:manual visualization of 3D terrain,automated visualization of 3D terrain,online visualization of 3D terrain,and software for visualizing 3D terrain.Then,the paper compares between the different types of systems developed by various authors based on the capabilities and the limitations of the system.Some of the techniques have their own strengths and limitations which solve the problem in 3D terrain visualization.However,the research on improving 3D terrain visualization is still ongoing.This is due to the popularity of online environments and mobile devices that render 3D terrain.This review paper will help interested users understand the current state of 3D terrain visualization of GIS data in a better way.展开更多
In this study, trends of minimum, average and maximum flows were investigated in Porsuk basin, which is a sub-basin of Sakarya basin and then changes in flows were mapped using Geographical Information Systems (GIS). ...In this study, trends of minimum, average and maximum flows were investigated in Porsuk basin, which is a sub-basin of Sakarya basin and then changes in flows were mapped using Geographical Information Systems (GIS). In the study, in 10 flow gauging stations across the Porsuk basin, monthly average, maximum and minimum flow data is used covering the period 1961-2013 (53 years). When analyzing the distribution of observed trends in the basin, a trend has been observed in most of the river flows. A decreasing trend has been observed overall in the basin. Trends are generally decreasing over time except for a few stations. As a result, increasing trends are observed in the west part of the basin;while in the east part of the basin decreasing trends are observed. When average and maximum monthly flows are investigated, decreasing trends are observed in the stations except DSI-12182. Trend analysis of 10 flow gauging stations across the Porsuk basin is investigated by Mann-Kendall method. Trend distribution was made according to flow trends of basin by transferring Z values to GIS.展开更多
Earthquake induced landslides are one of the most severe geo-environmental hazards that cause enormous damage to infrastructure, property, and loss of life in Nuweiba area. This study developed a model for mapping the...Earthquake induced landslides are one of the most severe geo-environmental hazards that cause enormous damage to infrastructure, property, and loss of life in Nuweiba area. This study developed a model for mapping the earthquake-induced landslide susceptibility in Nuweiba area in Egypt with considerations of geological, geomorphological, topographical, and seismological factors. An integrated approach of remote sensing and GIS technologies were applied for that target. Several data sources including Terra SAR-X and SPOT 5 satellite imagery, topographic maps, field data, and other geospatial resources were used to model landslide susceptibility. These data were used specifically to produce important thematic layers contributing to landslide occurrences in the region. A rating scheme was developed to assign ranks for the thematic layers and weights for their classes based on their contribution in landslide susceptibility. The ranks and weights were defined based on the knowledge from field survey and authors experiences related to the study area. The landslide susceptibility map delineates the hazard zones to three relative classes of susceptibility: high, moderate, and low. Therefore, the current approach provides a way to assess landslide hazards and serves for geo-hazard planning and prediction in Nuweiba area.展开更多
Security has recently become a major concern in distributed geo-infrastructures for spatial data provision.Thus,a lightweight approach for securing distributed low-power environments such as geo-sensor networks is nee...Security has recently become a major concern in distributed geo-infrastructures for spatial data provision.Thus,a lightweight approach for securing distributed low-power environments such as geo-sensor networks is needed.The first part of this article presents a survey of current security mechanisms for authentication and authorisation.Based on this survey,a lightweight and scalable token-based security infrastructure was developed,which is tailored for use in distributed geo-web service infrastructures.The developed security framework comprises dedicated components for authentication,rule-based authorisation and optimised storage and administration of access rules.For validation purposes,a prototypical implementation of the approach has been created.展开更多
Urban barriers are often a consequence of the unplanned expansion of transport infrastructures,housing growth nearby existing transport infrastructures,and the vehicular traffic itself.This process,also known as“comm...Urban barriers are often a consequence of the unplanned expansion of transport infrastructures,housing growth nearby existing transport infrastructures,and the vehicular traffic itself.This process,also known as“community severance”,is a problem that affects the travel patterns of the population and causes negative impacts to adjacent communities,but it is not easy to assess.As an alternative to the costly technologies and restricted-access data sometimes used to analyze urban barriers,we propose an analytical approach that assesses community severance levels by classifying the quality of Pedestrian Crossings on Urban Streets(the PeCUS index).Additionally,the approach is used to identify possible inequities nearby the different classification groups regarding demographic data.We used the chi-square(χ^(2))test of independence and the standardized Pearson residuals to indicate deficits and excesses of residents regarding the demographic characteristics studied surrounding the urban streets.We found the following evidences of associations:residents with low-income or those aged up to 19 tend to live close to the worst crossings,whereas residents with permanent mobility constraints or the elderly tend to live near the crossings with the best classifications.Therefore,the study shows that the assessment of community severance by the analysis of the PeCUS index is feasible.Moreover,it reveals that the distribution of residents surrounding the distinct classes of quality of crossings is equitable for vulnerable social groups,except for low-income or young residents.展开更多
This work focuses on examining the possible advantages for the urban sustainability,derived from the integration of transport,land use and energy systems.The main aim is to develop a GIS-based method that can help dec...This work focuses on examining the possible advantages for the urban sustainability,derived from the integration of transport,land use and energy systems.The main aim is to develop a GIS-based method that can help decision makers,either public or private,improve the economic,social and environmental sustainability of urban areas through an integrated transformation approach.As a result,it was possible to provide a spatial analysis technique based on seven synthetic variables and on the application of a cluster method able to identify the portions of urban areas where investments and urban integrated transformation processes can be more suitable,according to the dynamic relationships among transport,land use and energy systems.The methodology was applied to the Greater London area and led to significant results:the cluster classes follow the transport railway network evolution within the study area boundary.The paper is organized as follows:in Section 1 the integration of transport,land use and energy planning is investigated;following the introduction,in Section 2,the GIS-based method is presented,followed by a description of the application to the Greater London area;in Section 4,findings of the methodology are explained.In the last section,results and future developments are discussed.展开更多
A municipal solid waste(MSW)management system needs solid waste management(SWM)techniques where the presence of a sanitary landfill is vital.One of the most important issues of sanitary landfilling is to locate the f...A municipal solid waste(MSW)management system needs solid waste management(SWM)techniques where the presence of a sanitary landfill is vital.One of the most important issues of sanitary landfilling is to locate the facility to an optimal location.Despite the versatility and case-dependent nature of conventional expert-based site selection procedures,the number of sites to be chosen increases with increased population forcing a number of constraints.Consequently,constraints and environmental regulations mechanically mask unsuitable areas,leaving very little areas to be assessed.This turns the situation into a challenging issue for a geographical information system(GIS)used with multicriteria decision analysis(MCDA),to select optimal site.The study aims to apply MCDA integrated with GIS to select possible sites of a MSW landfill with the same expert and same cognitive parameters while compared with the already present one.Results of this study revealed that conventional expert-based methods could not always evaluate all constraints at the same time and map reproduction is limited when parameter maps are changing rapidly in time.In order to produce cognitive and reproducible analyses,GIS with MCDA integration offers a good solution for site selection issue and forms a good alternative for conventional methods.展开更多
This paper presents a new spatial data model based on trapezoidal-mesh for implementing spatial operations within geographical information systems(GIS).Based only on the solid foundation of spatial operations,diversif...This paper presents a new spatial data model based on trapezoidal-mesh for implementing spatial operations within geographical information systems(GIS).Based only on the solid foundation of spatial operations,diversified application models can be established to bridge the gap between Digital Earth models and the real world with its real-world problems(‘connecting through location’).In this paper,the involved polygon features are decomposed into a series of trapezoidalmeshes.Then,geo-processing operations are employed on these meshes rather than the original polygon features,resulting in a relatively simple spatial computation.As a kind of model designed by integrating raster with vector,the model presented here has advantages over other models when carrying out spatial operations insofar as providing a solid foundation for achieving the grand goal of Digital Earth.The concept of this data model and the two extensive examples of its application in spatial operations are elaborated upon in this article.As a result,this article and the research that supports it,proves that the adoption of the trapezoidal-mesh model greatly improves the efficiency of spatial operations in GIS.展开更多
基金supported by the International Scientific Joint Project of China (No. 2009DFA21280)the National Natural Science Foundation of China (No. 40821160550)the Doctoral Candidate Innovation Research Support Program by Science & Technology Review (No. kjdb200902-5)
文摘Tens of thousands of landslides were triggered by May 12, 2008 earthquake over a broad area. The main purpose of this article is to apply and verify earthquake-triggered landslide hazard analysis techniques by using weight of evidence modeling in Qingshui （清水） River watershed, Deyang （德阳） City, Sichuan （四川） Province, China. Two thousand three hundred and twenty-one landslides were interpreted in the study area from aerial photographs and multi-source remote sensing imageries post-earthquake, verified by field surveys. The landslide inventory in the study area was established. A spatial database, including landslides and associated controlling parameters that may have influence on the occurrence of landslides, was constructed from topographic maps, geological maps, and enhanced thematic mapper （ETM＋） remote sensing imageries. The factors that influence landslide occurrence,such as slope angle, aspect, curvature, elevation, flow accumulation, distance from drainages, and distance from roads were calculated from the topographic maps. Lithology, distance from seismogenic fault, distance from all faults, and distance from stratigraphic boundaries were derived from the geological maps. Normalized difference vegetation index （NDV1） was extracted from ETM＋ images. Seismic intensity zoning was collected from Wenchuan （汶川） Ms8.0 Earthquake Intensity Distribution Map published by the China Earthquake Administration.Landslide hazard indices were calculated using the weight of evidence model, and landslide hazard maps were calculated from using different controlling parameters cases. The hazard map was compared with known landslide locations and verified. The success accuracy percentage of using all 13 controlling parameters was 71.82%. The resulting landslide hazard map showed five classes of landslide hazard, i.e., very high, high, moderate, low, and very low. The validation results showed satisfactory agreement between the hazard map and the existing landslides distribution data.
基金funding from the National Science and Technology Major Project of the Ministry of Science and Technology of China[grant number 2017YFB0503605]the National Natural Science Foundation of China[grant number 41771478]+3 种基金the Fundamental Research Funds for the Central Universities[grant number 2019B02514]Natural Science Foundation of Beijing,China[grant number 8172046]the China Scholarship Council(CSC)Queen Mary University of London.
文摘The coronavirus disease 2019(COVID-19)and its mutant viruses are still wreaking global havoc over the last two years,but the impact of human activity on the transmission of the pandemic is difficult to ascertain.Estimating human dynamic spatiotemporal distribution can help in our understanding of how to mitigate COVID-19 spread,which can help in maintaining urban health within a county and between counties within a country.This distribution can be computed using the Volunteered Geographic Information(VGI)of the citizens in conjunction with other variables,such as climatic conditions,and used to analyze how human’s daily density distribution quantitatively affects COVID-19 transmission.Based on the estimated population density,when the population density increases daily by 1 person/km^(2) in a county or prefectural-level administrative unit with an average size of 26,000 km^(2),the county would have an additional 3.6 confirmed cases and 0.054 death cases after 5 days,which is the illness onset time for a new COVID-19 case.After 14 days,which is the maximum incubation period of the COVID-19 virus,there would be 5 new confirmed cases and 0.092 death cases.However,in neighboring regions,there can be 0.96 fewer people infected with COVID-19 on average per day as a result of strong intervention of local and neighboring authorities.The primary innovation and contribution are that this is the first quantitative assessment of the impacts of dynamic population density on the COVID-19 pandemic.Additionally,the direct and indirect effects of the impact are estimated using spatial panel models.The models that control the unobserved factors improve the reliability of the estimation,as validated by random experiments and the use of the Baidu migration dataset.
基金supported by the Japanese Government:Ministry of Science,Education,Sport and Technology“Mombukagakusho”a.k.a MEXT as part of a scholarship programthe APC was supported by the Open research fund program of LIESMARS,Wuhan University.
文摘According to many previous studies,application of remote sensing for the complex and heterogeneous urban environments in Sub-Saharan African countries is challenging due to the spectral confusion among features caused by diversity of construction materials.Resorting to classification based on spectral indices that are expected to better highlight features of interest and to be prone to unsupervised classification,this study aims(1)to evaluate the effectiveness of index-based classification for Land Use Land Cover(LULC)using an unsupervised machine learning algorithm Product Quantized K-means(PQk-means);and(2)to monitor the urban expansion of Luanda,the capital city of Angola in a Logistic Regression Model(LRM).Comparison with state-of-the-art algorithms shows that unsupervised classification by means of spectral indices is effective for the study area and can be used for further studies.The built-up area of Luanda has increased from 94.5 km2 in 2000 to 198.3 km2 in 2008 and to 468.4 km2 in 2018,mainly driven by the proximity to the already established residential areas and to the main roads as confirmed by the logistic regression analysis.The generated probability maps show high probability of urban growth in the areas where government had defined housing programs.
基金funding from Clemson University.This is technical contribution No.6345 of the Clemson University Experiment Stationsupported by NIFA/USDA,under project number SC-1700452
文摘Spatio-temporal patterns of flowering in forest ecosystems are hard to quantify and monitor. The objectives of this study were to investigate spatio-temporal patterns（e.g. soilssimple slope classesslope aspectand flow accumulation） of flowering around Lake IssaqueenaSouth Carolina（SCUSA） using plant-flowering database collected with GPS- enabled camera（stored in Picasa 3 web albums and project website） on a monthly basis in 2012 and Li DAR-based topography. Pacolet fine sandy loam had the most flowering plantsfollowed by Madison sandy loamboth dominant soil types around the lake. Most flowering plants were on moderately steep（17%–30%） and gently sloping（4%–8%） slopes. Most flowering plants were on west（247.5°–292.5°）southwest（202.5°–247.5°）and northwest（292.5°–337.5°） aspects. Most flowering plants were associated with minimum and maximum flows within the landscape. Chi-square tests indicated differences in the distributions of the proportions of flowering plants were significant by soil typeslopeaspectand flow accumulation for each month（February-November）for all months（overall）and across months. The Chi-square test on area-normalized data indicated significant differences for all months and individual differences by each month with some months not statistically significant. Cluster analysis on flowering counts for nine plant families with the most flowering counts indicated no unique separation by clusterbut implied that the majority of these families were flowering on strongly sloping（9%–16%） slopeson southwest（202.5°–247.5°） aspectsand low flow accumulation（0–200）. Presented methodology can serve as a template for future efforts to quantify spatio-temporal patterns of flowering and other phenological events.
文摘Since the introduction of geographic information systems(GIS)in the 1960s,it has evolved tremendously to an extent that it permeates our daily lives.Initially,GIS usage started in the developed countries and now increasingly filtered to developing countries.The town planning profession was one of the early adopters of GIS.Geospatial information is a useful source of data that is needed in urban planning.In these days of the New Urban Agenda 2030,smart cities are even more required from planners in using geospatial information to face urban challenges such as sustainable urban development and climate change.Although GIS has promised a lot for urban planning,it has not reached its full potential.Moreover,many studies have focused on developed countries with limited studies on geospatial information application in municipalities and GIS education from a perspective of developing countries.In this study,a survey on the usage of geospatial information science(GSIS)in two cities,namely Bulawayo in Zimbabwe and Ekurhuleni in South Africa,was conducted,and an overview of the state of GIS curricula in planning schools is discussed.The results indicate that considerable progress has been made in the application of geospatial information in municipal planning;however,there are impediments limiting the full utilization of geospatial information in local municipalities.These impediments include:inadequate GIS curricula in planning schools,lack of resources,and lack of political will.These challenges manifest differently in well-resourced municipalities and those with limited resources.The study proposes planning-relevant GIS curricula to improve the level of GIS use in planning practice.
文摘The aim of this study was to determine how well the landslide susceptibility parameters,obtained by data-dependent statistical models,matched with the parameters used in the literature.In order to achieve this goal,20 different environmental parameters were mapped in a well-studied landslide-prone area,the Asarsuyu catchment in northwest Turkey.A total of 4400 seed cells were generated from 47 different landslides and merged with different attributes of 20 different environmental causative variables into a database.In order to run a series of logistic regression models,different random landslide-free sample sets were produced and combined with seed cells.Different susceptibility maps were created with an average success rate of nearly 80%.The coherence among the models showed spatial correlations greater than 90%.Models converged in the parameter selection peculiarly,in that the same nine of 20 were chosen by different logistic regression models.Among these nine parameters,lithology,geological structure(distance/density),landcover-landuse,and slope angle were common parameters selected by both the regression models and literature.Accuracy assessment of the logistic models was assessed by absolute methods.All models were field checked with the landslides resulting from the 12 November 1999,Kaynas¸li Earthquake(Ms7.2).
基金Centre of Geographical Studies,No.UIDB/00295/2020,No.UIDP/00295/2020FCT–Portuguese Foundation for Science and Technology,I.P.,No.SFRH/BD/96632/2013,No.CEEIND/00268/2017Project Be Safe Slide,No.PTDC/GES-AMB/30052/2017。
文摘Water depths and flow velocities decisively influence the damage caused by flash floods.Geographic Information System(GIS)is a powerful and useful tool,allowing the spatial analysis of results obtained by hydraulic modelling,namely from the HEC-RAS/HEC-GeoRAS software.The GIS spatial analysis performed in this study seeks to explain and quantify the spatial relationships between the stream channel features and flow components during flash flood events.Despite these relationships are generically known,there are few studies exploring this subject in different geographic contexts.A 1D hydraulic model was applied in a small watershed in Portugal,providing good results in the definition of floodable areas,water depths and longitudinal velocities.No direct relationship was found between water depths and velocities in the floodable areas;however,negative strong correlations were found between the two flow components along the stream centerlines.Bed slope,channel and flood width,and roughness prove to be highly relevant on the longitudinal variations of water depths and velocities and on the location of maximum values.Increasing peak discharges and return periods(R;)can change the relationships between water depths and velocities at the same location.Results can be improved with more accurate elevation data for stream channels and floodplains.
基金supported by funds from a US National Science Foundation MacroSystems Biology award(1340746)the Portland State University College of Liberal Arts and Sciences.
文摘Dispersal is one of the most important but least understood processes in plant ecology and evolutionary biology.Dispersal of seeds maintains and establishes populations,and pollen and seed dispersal are responsible for gene flow within and among populations.Traditional views of dispersal and gene flow assume models that are governed solely by geographic distance and do not account for variation in dispersal vector behavior in response to heterogenous landscapes.Landscape genetics integrates population genetics with Geographic Information Systems(GIS)to evaluate the effects of landscape features on gene flow patterns(effective dispersal).Surprisingly,relatively few landscape genetic studies have been conducted on plants.Plants present advantages because their populations are stationary,allowing more reliable estimates of the effects of landscape features on effective dispersal rates.On the other hand,plant dispersal is intrinsically complex because it depends on the habitat preferences of the plant and its pollen and seed dispersal vectors.We discuss strategies to assess the separate contributions of pollen and seed movement to effective dispersal and to delineate the effects of plant habitat quality from those of landscape features that affect vector behavior.Preliminary analyses of seed dispersal for three species indicate that isolation by landscape resistance is a better predictor of the rates and patterns of dispersal than geographic distance.Rates of effective dispersal are lower in areas of high plant habitat quality,which may be due to the effects of the shape of the dispersal kernel or to movement behaviors of biotic vectors.Landscape genetic studies in plants have the potential to provide novel insights into the process of gene flow among populations and to improve our understanding of the behavior of biotic and abiotic dispersal vectors in response to heterogeneous landscapes.
文摘Almost all causative factors of diseases depend on location.The Digital Earth approach is suitable for studying diseases globally.Geospatial information systems integrated with statistical models can be used to model the relationship between a disease and its causative factors.Through modelling,the most important causative factors can be extracted and the epidemiology of the disease can be observed.In this paper,skin cancer(the most common type of cancer)has been modelled based on its causative factors,including climate factors,people’s occupations,nutrition habits,socio-economic factors,and usage of chemical fertiliser.To fit the model,a data framework was first designed,and then data were gathered and processed.Finally,the disease was modelled using Generalised Linear Models(GLM),a statistical model based on the location of the factors.The results of this study identify the most important causative factors together with their relative priority.Furthermore,a model was used to predict the change in skin cancer occurrences caused by a change in one of its causative factors.This work illustrates the ability of the model to predict disease occurrence.Thus,by using this Digital Earth approach,skincancer can be studied in all the key countries around the world.
文摘3D terrain visualization of geographic information systems(GIS)data has become an important issue in recent years.This is due to the emergence of new geo-browsers such as Google Earth,widely popular among users.The availability of 3D representation tools has increased the demand for 3D terrain visualization.The aim of this paper is to review the literature related to the 3D terrain visualization of GIS data from the first map produced until the online mapping era.The reviews are divided into four different sections:manual visualization of 3D terrain,automated visualization of 3D terrain,online visualization of 3D terrain,and software for visualizing 3D terrain.Then,the paper compares between the different types of systems developed by various authors based on the capabilities and the limitations of the system.Some of the techniques have their own strengths and limitations which solve the problem in 3D terrain visualization.However,the research on improving 3D terrain visualization is still ongoing.This is due to the popularity of online environments and mobile devices that render 3D terrain.This review paper will help interested users understand the current state of 3D terrain visualization of GIS data in a better way.
基金This study was supported by the project 1506F500 accepted by Anadolu University Scientific Research Projects Commission.
文摘In this study, trends of minimum, average and maximum flows were investigated in Porsuk basin, which is a sub-basin of Sakarya basin and then changes in flows were mapped using Geographical Information Systems (GIS). In the study, in 10 flow gauging stations across the Porsuk basin, monthly average, maximum and minimum flow data is used covering the period 1961-2013 (53 years). When analyzing the distribution of observed trends in the basin, a trend has been observed in most of the river flows. A decreasing trend has been observed overall in the basin. Trends are generally decreasing over time except for a few stations. As a result, increasing trends are observed in the west part of the basin;while in the east part of the basin decreasing trends are observed. When average and maximum monthly flows are investigated, decreasing trends are observed in the stations except DSI-12182. Trend analysis of 10 flow gauging stations across the Porsuk basin is investigated by Mann-Kendall method. Trend distribution was made according to flow trends of basin by transferring Z values to GIS.
基金the Egyptian Ministry of Higher Education and Scientific Research
文摘Earthquake induced landslides are one of the most severe geo-environmental hazards that cause enormous damage to infrastructure, property, and loss of life in Nuweiba area. This study developed a model for mapping the earthquake-induced landslide susceptibility in Nuweiba area in Egypt with considerations of geological, geomorphological, topographical, and seismological factors. An integrated approach of remote sensing and GIS technologies were applied for that target. Several data sources including Terra SAR-X and SPOT 5 satellite imagery, topographic maps, field data, and other geospatial resources were used to model landslide susceptibility. These data were used specifically to produce important thematic layers contributing to landslide occurrences in the region. A rating scheme was developed to assign ranks for the thematic layers and weights for their classes based on their contribution in landslide susceptibility. The ranks and weights were defined based on the knowledge from field survey and authors experiences related to the study area. The landslide susceptibility map delineates the hazard zones to three relative classes of susceptibility: high, moderate, and low. Therefore, the current approach provides a way to assess landslide hazards and serves for geo-hazard planning and prediction in Nuweiba area.
基金This work has been funded by the European Commission(FP7 project GENESIS,reference No.223996)the Austrian Federal Ministry for Science and ResearchThe au。
文摘Security has recently become a major concern in distributed geo-infrastructures for spatial data provision.Thus,a lightweight approach for securing distributed low-power environments such as geo-sensor networks is needed.The first part of this article presents a survey of current security mechanisms for authentication and authorisation.Based on this survey,a lightweight and scalable token-based security infrastructure was developed,which is tailored for use in distributed geo-web service infrastructures.The developed security framework comprises dedicated components for authentication,rule-based authorisation and optimised storage and administration of access rules.For validation purposes,a prototypical implementation of the approach has been created.
基金This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code[001].
文摘Urban barriers are often a consequence of the unplanned expansion of transport infrastructures,housing growth nearby existing transport infrastructures,and the vehicular traffic itself.This process,also known as“community severance”,is a problem that affects the travel patterns of the population and causes negative impacts to adjacent communities,but it is not easy to assess.As an alternative to the costly technologies and restricted-access data sometimes used to analyze urban barriers,we propose an analytical approach that assesses community severance levels by classifying the quality of Pedestrian Crossings on Urban Streets(the PeCUS index).Additionally,the approach is used to identify possible inequities nearby the different classification groups regarding demographic data.We used the chi-square(χ^(2))test of independence and the standardized Pearson residuals to indicate deficits and excesses of residents regarding the demographic characteristics studied surrounding the urban streets.We found the following evidences of associations:residents with low-income or those aged up to 19 tend to live close to the worst crossings,whereas residents with permanent mobility constraints or the elderly tend to live near the crossings with the best classifications.Therefore,the study shows that the assessment of community severance by the analysis of the PeCUS index is feasible.Moreover,it reveals that the distribution of residents surrounding the distinct classes of quality of crossings is equitable for vulnerable social groups,except for low-income or young residents.
文摘This work focuses on examining the possible advantages for the urban sustainability,derived from the integration of transport,land use and energy systems.The main aim is to develop a GIS-based method that can help decision makers,either public or private,improve the economic,social and environmental sustainability of urban areas through an integrated transformation approach.As a result,it was possible to provide a spatial analysis technique based on seven synthetic variables and on the application of a cluster method able to identify the portions of urban areas where investments and urban integrated transformation processes can be more suitable,according to the dynamic relationships among transport,land use and energy systems.The methodology was applied to the Greater London area and led to significant results:the cluster classes follow the transport railway network evolution within the study area boundary.The paper is organized as follows:in Section 1 the integration of transport,land use and energy planning is investigated;following the introduction,in Section 2,the GIS-based method is presented,followed by a description of the application to the Greater London area;in Section 4,findings of the methodology are explained.In the last section,results and future developments are discussed.
基金Scientific&Technological Research Council of Turkey(TUBI˙TAK)for providing financial support of this work under Grant No:106Y305.
文摘A municipal solid waste(MSW)management system needs solid waste management(SWM)techniques where the presence of a sanitary landfill is vital.One of the most important issues of sanitary landfilling is to locate the facility to an optimal location.Despite the versatility and case-dependent nature of conventional expert-based site selection procedures,the number of sites to be chosen increases with increased population forcing a number of constraints.Consequently,constraints and environmental regulations mechanically mask unsuitable areas,leaving very little areas to be assessed.This turns the situation into a challenging issue for a geographical information system(GIS)used with multicriteria decision analysis(MCDA),to select optimal site.The study aims to apply MCDA integrated with GIS to select possible sites of a MSW landfill with the same expert and same cognitive parameters while compared with the already present one.Results of this study revealed that conventional expert-based methods could not always evaluate all constraints at the same time and map reproduction is limited when parameter maps are changing rapidly in time.In order to produce cognitive and reproducible analyses,GIS with MCDA integration offers a good solution for site selection issue and forms a good alternative for conventional methods.
文摘This paper presents a new spatial data model based on trapezoidal-mesh for implementing spatial operations within geographical information systems(GIS).Based only on the solid foundation of spatial operations,diversified application models can be established to bridge the gap between Digital Earth models and the real world with its real-world problems(‘connecting through location’).In this paper,the involved polygon features are decomposed into a series of trapezoidalmeshes.Then,geo-processing operations are employed on these meshes rather than the original polygon features,resulting in a relatively simple spatial computation.As a kind of model designed by integrating raster with vector,the model presented here has advantages over other models when carrying out spatial operations insofar as providing a solid foundation for achieving the grand goal of Digital Earth.The concept of this data model and the two extensive examples of its application in spatial operations are elaborated upon in this article.As a result,this article and the research that supports it,proves that the adoption of the trapezoidal-mesh model greatly improves the efficiency of spatial operations in GIS.
