The Loess positive and negative terrains （P-N terrains）, which are widely distributed on the Loess Plateau, are discussed for the first time by introducing its characteristic, demarcation as well as extraction metho...The Loess positive and negative terrains （P-N terrains）, which are widely distributed on the Loess Plateau, are discussed for the first time by introducing its characteristic, demarcation as well as extraction method from high-resolution Digital Elevation Models. Using 5 m-resolution DEMs as original test data, P-N terrains of 48 geomorphological units in different parts of Shaanxi Loess Plateau are extracted accurately. Then six indicators for depicting the geomorphologic landscape and spatial configuration characteristic of P-N terrains are proposed. The spatial distribution rules of these indicators and the relationship between the P-N terrains and Loess relief are discussed for further understanding of Loess landforms. Finally, with the integration of P-N terrains and traditional terrain indices, a series of un-supervised classification methods are applied to make a proper landform classification in northern Shaanxi. Results show that P-N terrains are an effect clue to reveal energy and substance distribution rules on the Loess Plateau. A continuous change of P-N terrains from south to north in Shaanxi Loess Plateau shows an obvious spatial difference of Loess land-forms and the positive terrain area only accounted for 60.5% in this region. The P-N terrains participant landform classification method increases validity of the result, especially in the Loess tableland, Loess tableland-ridge and the Loess low-hill area. This research is significant on the study of Loess landforms with the Digital Terrains Analysis methods.展开更多
The positive and negative terrains(P-N terrains) widely distributed across China's Loess Plateau constitute the dual structure characteristic of loess landforms. Analysis of loess P-N terrains at the watershed sca...The positive and negative terrains(P-N terrains) widely distributed across China's Loess Plateau constitute the dual structure characteristic of loess landforms. Analysis of loess P-N terrains at the watershed scale can serve to elucidate the structural characteristics and spatial patterns of P-N terrains, which benefits a better understanding of watershed evolution and suitable scales for loess landform research. The Two-Term Local Quadrat Variance Analysis(TTLQV) is calculated as the average of the square of the difference between the block totals of all possible adjacent pairs of block size, which can be used to detect both the scale and the intensity of landscape patches(e.g., plant/animal communities and gully networks). In this study, we determined the latitudinal and longitudinal spatial scale of P-N terrain patterns within 104 uniformly distributed watersheds in our target soil and water conservation region. The results showed that TTLQV is very effective for examining the scale of P-N terrain patterns. There were apparently three types of P-N terrain pattern in latitudinal direction(i.e., Loess Tableland type, Loess Hill type, and Transitional Form between Sand and Loess type), whereas there were both lower and higher values for P-N terrain pattern scales in all loess landforms in the longitudinal direction. The P-N terrain pattern alsoclearly presented anisotropy, suggesting that gully networks in the main direction were well-developed while others were relatively undeveloped. In addition, the relationships between the first scales and controlling factors(i.e., gully density, nibble degree, watershed area, mean watershed slope, NDVI, precipitation, loess thickness, and loess landforms) revealed that the first scales are primarily controlled by watershed area and loess landforms. This may indicate that the current spatial pattern of P-N terrains is characterized by internal force. In selecting suitable study areas in China' Loess Plateau, it is crucial to understand four control variables: the spatial scale of the P-N terrain pattern, the watershed area, the main direction of the watershed, and the loess landforms.展开更多
Local temperature changes in mountain areas are significantly affected by the uplifted mountain terrains. Understanding how temperature increase with mountain terrains is an important component in accurately modeling ...Local temperature changes in mountain areas are significantly affected by the uplifted mountain terrains. Understanding how temperature increase with mountain terrains is an important component in accurately modeling the spatial distribution of temperature. The study, after minimizing the effect of elevation and latitude, quantitatively simulated the temperature increase in the uplifted mountain terrains, described the characteristics in the spatial distribution of warming areas with different magnitudes, and identified the correlated indices of mountain bodies for warming. Selecting Yunnan Province in southwest China as the study area, we simulated the warming field on a baseline surface at the average elevation of 2000 m and average latitude of 24.96°. The results indicated that the warming magnitudes in different local areas varied with the change in the spatial locations, and the warming process concentrated in the mountainous regions. Throughout the entire study area, the warming field presented a general pattern of three terraces from the regions of high mountains to middle mountains and then low mountains. The areasof high warming magnitude mainly surrounded large mountain bodies and were distributed on the upper part. The areas of low warming magnitude clustered in the valleys and basins of the middle mountain region, mostly on the lower part of the large mountain bodies and its branches. The areas with zero warming magnitude occurred in the low mountains and broad valleys, which were distributed largely on the lower parts of the middle mountains and in most of the valleys. Quantified sampling analysis demonstrated good positive correlation between the warming magnitudes in uplifted mountain terrains and the volume index of the mountain body, as well as elevation difference, with the coefficients corresponding to 0.82 and 0.91, respectively.展开更多
The effect of wind environment is becoming increasingly important in analyzing and selecting sites for better naturalventilation of residential buildings, external comfort, and pollution dispersion. The mainpurpose of...The effect of wind environment is becoming increasingly important in analyzing and selecting sites for better naturalventilation of residential buildings, external comfort, and pollution dispersion. The mainpurpose of this study was to develop a setof methods for wind environment assessment in coastal concave terrains. This set of methods can be used to provide quantifiableindicators of preferable wind conditions and help site analysis. Firstly, a total of 20 types of coastal bays with concave terrains inEast Asia were characterized to find ideal locations. The selected areas were divided into five categories according to the mainterrain features. Then a sample database for the concave terrains was compiled for modelling comparisons. Secondly, a number ofkey wind variables were identified. Computational fluid dynamics （CFD） models of the typical coastal concave terrains identifiedas a result of the study were created, and the local wind environments were simulated with input from geographic informationsystem （GIS） and statistic package for social science （SPSS） analysis. A measure of wind suitability was proposed that takes windvelocity and wind direction into account using GIS. Finally, SPSS was used to find the relationship between wind suitability andkey terrain factors. The results showed that wind suitability was significantly associated with terrain factors, especially altitude.The results suggest that residential building sites should be selected such that their bay openings face the direction of the prevailingwind and that the opposite direction should be avoided.展开更多
The classification of thematic mapper imagery in areas with strong topographic variations has proven problematic in the past using a single classifier, due to the changing sun illumination geometry. This often results...The classification of thematic mapper imagery in areas with strong topographic variations has proven problematic in the past using a single classifier, due to the changing sun illumination geometry. This often results in the phenomena of identical object with dissimilar spectrum and different objects with similar spectrum. In this paper, an integrated classification method that combines a decision tree with slope data, tasseled cap transformation indices and maximum likelihood classifier is introduced, to find an optimal classification method for thematic mapper imagery of plain and highland terrains. A Landsat 7 ETM+ image acquired over Hangzhou Bay, in eastern China was used to test the method. The results indicate that the performance of the inte- grated classifier is acceptably good in comparison with that of the existing most widely used maximum likelihood classifier. The integrated classifier depends on hypsography (variation in topography) and the characteristics of ground truth objects (plant and soil). It can greatly reduce the influence of the homogeneous spectrum caused by topographic variation. This integrated classifier might potentially be one of the most accurate classifiers and valuable tool for land cover and land use mapping of plain and highland terrains.展开更多
In order to evaluate the impact of off-road terrains on the ride comfort of construction vehicles,a nonlinear dynamic model of the construction vehicles interacting with the terrain deformations is established based o...In order to evaluate the impact of off-road terrains on the ride comfort of construction vehicles,a nonlinear dynamic model of the construction vehicles interacting with the terrain deformations is established based on Matlab/Simulink software.The weighted root mean square(RMS)acceleration responses and the power spectral density(PSD)acceleration responses of the driver s seat heave,the pitch and roll angle of the cab in the low-frequency region are chosen as objective functions under different operation conditions of the vehicle.The results show that the impact of off-road terrains on the driver s ride comfort and health is clear under various conditions of deformable terrains and range of vehicle velocities.In particular,the driver s ride comfort is greatly affected by a soil terrain while the comfortable shake of the driver is strongly affected by a sand terrain.In addition,when the vehicle travels on a poor soil terrain in the frequency range below 4 Hz,more resonance peaks of acceleration PSD responses occurred than that on a rigid road of ISO 2631-1 level C.Thus,the driver s health is significantly affected by the deformable terrain in a low-frequency range.展开更多
In Pakistan,the solar analogue has been addressed but its surface geographical parameterization has given least attention.Inappropriate density of stations and their spatial coverage particularly in difficult peripher...In Pakistan,the solar analogue has been addressed but its surface geographical parameterization has given least attention.Inappropriate density of stations and their spatial coverage particularly in difficult peripheral national territories,little or no solar radiation data,non-satisfactory sunshine hours data,and low quality of ground observed cloud cover data create a situation in which the spatial modeling of Extraterrestrial Solar Radiation(ESR) and its ground parameterization got sufficient scope.The Digital Elevation Model (DEM) input into Geographic Information System (GIS) is a compatible tool to demonstrate the spatial distribution of ESR over the rugged terrains of the study domain.For the first time,distributed modeling of ESR is done over the rugged terrains of Pakistan,based on DEM and ArcGIS..Results clearly depict that the complex landforms profoundly disrupt the zonal distribution of ESR in Pakistan.The screening impact of topography is higher on spatial distribution of ESR in winter and considerably low in summer.The combined effect of topography and latitude is obvious.Hence,the model was further testified by plotting Rb (ratio of ESR quantity over rugged terrain against plane surface) against azimuth at different latitudes with different angled slopes.The results clearly support the strong screening effect of rugged terrain through out the country especially in Himalayas,Karakoram and Hindukush (HKH),western border mountains and Balochistan Plateau.This model can be instrumental as baseline geospatial information for scientific investigations in Pakistan,where substantial fraction of national population is living in mountainous regions.展开更多
The major results about magnetic petrology of Archearn high grade terrains in the world are reviewed in this article, focusing on the relationship between rock magnetism and deformation, and metamorphism and intensit...The major results about magnetic petrology of Archearn high grade terrains in the world are reviewed in this article, focusing on the relationship between rock magnetism and deformation, and metamorphism and intensity of magnetization of the lower continental crust. The important problems about the magnetic study of rocks for high grade terrains are advanced.展开更多
The research was carried out in Dar es Salaam’s Makongo and Goba neighbourhoods using an exploratory method covering 200 questionnaires,100 for Goba and 100 for Makongo respectively.There were two significant issues ...The research was carried out in Dar es Salaam’s Makongo and Goba neighbourhoods using an exploratory method covering 200 questionnaires,100 for Goba and 100 for Makongo respectively.There were two significant issues observed:To begin,data from 2003 to 2017 reveal a large increase in urbanisation in both locations.Furthermore,urbanisation led to an increase in hard surface areas,which,according to the analysis,contributed to an increase in surface runoff,which had detrimental consequences for hilly residential settlements,resulting in downstream floods,building destruction,and loss of life and properties.Few residents were aware of water harvesting methods as a technique to deal with surface runoff,but they were not aware that they might be used to harvest water for future use.Policy to harvest,retain and use rainwater is recommended,whereby each plot owner should contain water from his/her plot by harvesting,collecting and retaining it for home use such as farming,fish ponds and other uses.展开更多
Coverage is an important issue in the area of wireless sensor networks, which reflects the monitoring quality of the sensor networks in scenes. Most sensor coverage research focuses on the ideal two-dimensional （2-D...Coverage is an important issue in the area of wireless sensor networks, which reflects the monitoring quality of the sensor networks in scenes. Most sensor coverage research focuses on the ideal two-dimensional （2-D） plane and full three-dimensional （3-D） space. However, in many real-world applications, the target field is a 3-D complex surface, which makes conventional methods unsuitable. In this paper, we study the coverage problem in directional sensor networks for complex 3-D terrains, and design a new surface coverage algorithm. Based on a 3-D directional sensing model of nodes, this algorithm employs grid division, simulated annealing, and local optimum ideas to improve the area coverage ratio by optimizing the position coordinates and the deviation angles of the nodes, which results in coverage enhancement for complex 3-D terrains. We also conduct extensive simulations to evaluate the performance of our algorithms.展开更多
Terrain Aided Navigation(TAN)technology has become increasingly important due to its effectiveness in environments where Global Positioning System(GPS)is unavailable.In recent years,TAN systems have been extensively r...Terrain Aided Navigation(TAN)technology has become increasingly important due to its effectiveness in environments where Global Positioning System(GPS)is unavailable.In recent years,TAN systems have been extensively researched for both aerial and underwater navigation applications.However,many TAN systems that rely on recursive Unmanned Aerial Vehicle(UAV)position estimation methods,such as Extended Kalman Filters(EKF),often face challenges with divergence and instability,particularly in highly non-linear systems.To address these issues,this paper proposes and investigates a hybrid two-stage TAN positioning system for UAVs that utilizes Particle Filter.To enhance the system’s robustness against uncertainties caused by noise and to estimate additional system states,a Fuzzy Particle Filter(FPF)is employed in the first stage.This approach introduces a novel terrain composite feature that enables a fuzzy expert system to analyze terrain non-linearities and dynamically adjust the number of particles in real-time.This design allows the UAV to be efficiently localized in GPS-denied environments while also reducing the computational complexity of the particle filter in real-time applications.In the second stage,an Error State Kalman Filter(ESKF)is implemented to estimate the UAV’s altitude.The ESKF is chosen over the conventional EKF method because it is more suitable for non-linear systems.Simulation results demonstrate that the proposed fuzzy-based terrain composite method achieves high positional accuracy while reducing computational time and memory usage.展开更多
Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion.Quantitative analyses on loess landform have been employed from v...Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion.Quantitative analyses on loess landform have been employed from various perspectives.Peak intervisibility can provide the potential topographic information implied in the visual connectivity of peaks,however,its application in loess landform analysis remains unexplored.In this study,the interwoven sightlines among peaks,representing peak intervisibility,were extracted from the digital elevation model and simulated into a peak intervisibility network(PIN).Nine indices were proposed to quantify the PIN.Through a case study in Northern Shaanxi,China,three tasks were conducted,including,landform interpretation,spatial pattern mining,and landform classification.The main findings are as follows:(1)PIN responds to terrain morphology and is beneficial for loess landform interpretation.(2)The spatial patterns of PIN indices are heterogeneous and strongly coupled with the terrain morphologies,showing anisotropy and autocorrelation in spatial variations.(3)Using the light gradient boost machine classifier,the PIN index-based classification reaches a mean accuracy of 86.09%,an overall accuracy of 86%and a kappa coefficient of 0.84.These findings shed light on the applicability of PIN in loess landform analysis.Peak intervisibility not only enriches the theories and methodologies of relation-based digital terrain analysis,but also enhances our comprehension of loess landform genesis,morphology,distribution,and evolution.展开更多
Typhoons,as strong convective systems,can excite multi-scale atmospheric gravity waves that travel long distances,and play an important role in momentum and energy transmission between the middle and upper atmosphere....Typhoons,as strong convective systems,can excite multi-scale atmospheric gravity waves that travel long distances,and play an important role in momentum and energy transmission between the middle and upper atmosphere.In this paper,the research progress in the observation techniques,generation mechanism and propagation characteristics of typhoon-induced gravity waves were systematically reviewed.These studies show that based on the combined application of ground-based and space-based observation(sounding balloons,airglow imaging,and satellite remote sensing)and reanalysis data(such as ERA5),with the aid of ray tracing theory and numerical simulation technology,the mechanism of typhoon induced gravity waves and its dynamic characteristics in the middle and upper atmosphere have been better revealed.At present,there are still some insufficiencies in the fields of propagation path tracking of gravity waves,terrain multi-scale effect modeling and parameterization of inertial gravity waves,which need to be further studied in the future.展开更多
With the advancement of deep learning in the automotive domain,more and more researchers are focusing on autonomous driving.Among these tasks,free space detection is particularly crucial.Currently,many model-based app...With the advancement of deep learning in the automotive domain,more and more researchers are focusing on autonomous driving.Among these tasks,free space detection is particularly crucial.Currently,many model-based approaches have achieved autonomous driving on well-structured urban roads,but these efforts primarily focus on urban road environments.In contrast,there are fewer deep learningmethods specifically designed for off-road traversable area detection,and their effectiveness is not yet satisfactory.This is because detecting traversable areas in complex outdoor environments poses significant challenges,and current methods often rely on single-image inputs,which do not align with contemporary multimodal approaches.Therefore,in this study,we propose a CFH-Net model for off-road traversable area detection.This model employs a Transformer architecture to enhance its capability of capturing global information.For multimodal feature extraction and fusion,we integrate the CM-FRM module for feature extraction and introduce the novel FFX module for feature fusion,thereby improving the perception capability of autonomous vehicles on unstructured roads.To address upsampling,we propose a new convolution precorrection method to reduce model parameters and computational complexity while enhancing the model’s ability to capture complex features.Finally,we conducted experiments on the ORFD off-road dataset and achieved outstanding results.展开更多
Geomorphometric modeling and mapping of Antarctic oases are promising for obtaining new quantitative knowledge about the topography of these unique landscapes and for the further use of morphometric information in Ant...Geomorphometric modeling and mapping of Antarctic oases are promising for obtaining new quantitative knowledge about the topography of these unique landscapes and for the further use of morphometric information in Antarctic research.Within the framework of a project to create a thematic physical-geographical scientific reference geomorphometric atlas of ice-free areas of Antarctica,we performed geomorphometric modeling and mapping of the Bunger Hills(Knox Coast,Wilkes Land,East Antarctica),one of the largest Antarctic oases.By processing a fragment of the Reference Elevation Model of Antarctica(REMA)covering the Bunger Hills and adjacent glaciers,we created,for the first time,a series of 37 medium-to large-scale maps of nine of the most scientifically important morphometric variables(i.e.,slope gradient,slope aspect,vertical curvature,horizontal curvature,maximal curvature,minimal curvature,catchment area,topographic wetness index,and stream power index).The morphometric maps describe the topography of the Bunger Hills in a quantitative,rigorous,and reproducible manner.New morphometric data can be useful for further geological,geomorphological,glaciological,ecological,and hydrological studies of this Antarctic oasis.展开更多
Tafoni are globally developed on cliffy slopes,and many of them are favorable places for the preservation of stone historical relics.However,the characteristics and formation processes of tafoni in the Loess Plateau a...Tafoni are globally developed on cliffy slopes,and many of them are favorable places for the preservation of stone historical relics.However,the characteristics and formation processes of tafoni in the Loess Plateau are yet to be understood.This paper studied the features of the tafoni on conglomerate slopes in Huoshizhai National Geopark of Ningxia Hui Autonomous Region and discussed its formation processes by field investigation and morphometry,insitu relative humidity(RH)measurement,salt chemistry and X-ray fluorescence spectrometer(XRF)experiments of 24 samples.The bedrock of the tafoni is dominated by reddish fluvial conglomerates of the Lower Cretaceous Heshangpu Formation with abundant chemically unstable components including feldspars,lithic fragments,and calcite cements.The RH values vary from 5%to 100%,but the backwalls of the tafoni have higher RH values than outer surfaces.The more moisture on the backwalls is possibly generated by water influx from the rock interior,resulting in more salt precipitation on the backwalls.As a result,the backwalls have been subject to predominant salt weathering.The dominant salts involved in salt weathering are probably derived from the dissolution of the salt interbeds in the basin,although the chemical dissolution of the unstable components such as feldspars,lithic fragments,and calcite cements might have produced small amounts of salts.The salt types dominantly include nitrates,sulfates,and halite.In the progression of tafoni,the moisture maintenance on the backwalls gives rise to the accretion of salts,which in turn enhance the weathering rates of the backwalls.As a result,the volumes of the tafoni have become enlarged owing to inward growth and coalescence of adjacent smaller ones.展开更多
The Hengduan Mountains,situated on the southeastern edge of the Qinghai-Tibet Plateau,are the longest and widest north-south-oriented mountain range in China,exerting a significant influence on the ecological and geog...The Hengduan Mountains,situated on the southeastern edge of the Qinghai-Tibet Plateau,are the longest and widest north-south-oriented mountain range in China,exerting a significant influence on the ecological and geographical pattern.Understanding the topographic and geomorphological characteristics of the Hengduan Mountains is fundamental and crucial for research in related fields such as ecology,geography,and sustainability.In this study,Digital Elevation Model(DEM)data were utilized to extract and analyze the topography and geomorphology(TG)pattern.TG maps have been developed to quantitatively classify the TG types in the Hengduan Mountains by combining the five factors of elevation,slope,aspect,relief and landform.The spatial distribution and quantitative characteristics of these factors were mapped and investigated using geographic information systems.The results revealed that:(1)The Hengduan Mountains exhibit an elongated north-south distribution,with an average elevation of approximately 3746 m,an average slope of around 25°,and an average relief of about 266 m.(2)The Hengduan Mountains display significant elevation differences,with an overall high elevation,characterized by a trend of lower elevation in the east and higher elevation in the west,as well as irregular orientations of various aspects.(3)The 19 landform types were identified,the landform types of the Hengduan Mountains are primarily composed of low-relief high-mountains(42.0618%),low-relief mid-mountains(22.4624%),and high-elevation hills(20.5839%).The results of the study can provide data and information support for the ecology,environmental protection and sustainable development of the Hengduan Mountains.展开更多
Unmanned aerial vehicle light detection and ranging(UAV–LiDAR)is a new method for collecting understory terrain data.The high estimation accuracy of understory terrain is crucial for accurate tree height measurement ...Unmanned aerial vehicle light detection and ranging(UAV–LiDAR)is a new method for collecting understory terrain data.The high estimation accuracy of understory terrain is crucial for accurate tree height measurement and forest resource surveys.The UAV–LiDAR flight altitude and forest canopy cover significantly impact the accuracy of understory terrain estimation.However,since no research examined their combined effects,we aimed to investigate this relationship.This will help optimize UAV–LiDAR flight parameters for understory terrain estimation and forest surveys across various canopy cover.This study analyzed the impacts of three flight altitudes and three canopy cover on the estimation accuracy of understory terrain.The results showed that when canopy cover exceeded a specific value,UAV–LiDAR flight altitudes significantly affected understory terrain estimation.Given a forest canopy cover,the reduction in ground point coverage increased significantly as the flight altitude increased;given a flight altitude,the higher the canopy cover,the more significant the reduction in ground point coverage.In forests with a canopy cover≥0.9,there were substantial differences in the accuracies of understory digital elevation models(DEMs)generated using UAV–LiDAR at different flight altitudes.For forests with a canopy cover<0.9,the mean absolute error(MAE)of understory DEMs from UAV–LiDAR at different flight altitudes was≤0.17 m and the root mean square error(RMSE)was≤0.24 m.However,for forests with a canopy cover≥0.9,the UAV–LiDAR flight altitude significantly affected the accuracy of understory DEMs.At the same flight altitude,the MAE and RMSE of the estimated elevation for forests with a canopy cover≥0.9 were approximately twice those of the estimated elevation for forests with a canopy cover<0.9.In forests with low canopy cover,it is possible to improve data collection efficiency by selecting a higher flight altitude.However,UAV–LiDAR flight altitudes significantly affected understory terrain estimation in forests with high canopy cover,it is essential to adopt terrain-following flight modes,reduce flight altitudes,and maintain a consistent flight altitude during longterm monitoring in high canopy cover forests.展开更多
基金Key Project of National Natural Science Foundation of China, No.40930531 National Youth Science Foundation of China, No.40801148 Anhui Provincial Natural Science Foundation. No. 090412062
文摘The Loess positive and negative terrains （P-N terrains）, which are widely distributed on the Loess Plateau, are discussed for the first time by introducing its characteristic, demarcation as well as extraction method from high-resolution Digital Elevation Models. Using 5 m-resolution DEMs as original test data, P-N terrains of 48 geomorphological units in different parts of Shaanxi Loess Plateau are extracted accurately. Then six indicators for depicting the geomorphologic landscape and spatial configuration characteristic of P-N terrains are proposed. The spatial distribution rules of these indicators and the relationship between the P-N terrains and Loess relief are discussed for further understanding of Loess landforms. Finally, with the integration of P-N terrains and traditional terrain indices, a series of un-supervised classification methods are applied to make a proper landform classification in northern Shaanxi. Results show that P-N terrains are an effect clue to reveal energy and substance distribution rules on the Loess Plateau. A continuous change of P-N terrains from south to north in Shaanxi Loess Plateau shows an obvious spatial difference of Loess land-forms and the positive terrain area only accounted for 60.5% in this region. The P-N terrains participant landform classification method increases validity of the result, especially in the Loess tableland, Loess tableland-ridge and the Loess low-hill area. This research is significant on the study of Loess landforms with the Digital Terrains Analysis methods.
基金supported by the National Natural Science Foundation of China (NO. 41201464, 41371424)the Fundamental Research Funds for the Central Universities of China (GK201703042)
文摘The positive and negative terrains(P-N terrains) widely distributed across China's Loess Plateau constitute the dual structure characteristic of loess landforms. Analysis of loess P-N terrains at the watershed scale can serve to elucidate the structural characteristics and spatial patterns of P-N terrains, which benefits a better understanding of watershed evolution and suitable scales for loess landform research. The Two-Term Local Quadrat Variance Analysis(TTLQV) is calculated as the average of the square of the difference between the block totals of all possible adjacent pairs of block size, which can be used to detect both the scale and the intensity of landscape patches(e.g., plant/animal communities and gully networks). In this study, we determined the latitudinal and longitudinal spatial scale of P-N terrain patterns within 104 uniformly distributed watersheds in our target soil and water conservation region. The results showed that TTLQV is very effective for examining the scale of P-N terrain patterns. There were apparently three types of P-N terrain pattern in latitudinal direction(i.e., Loess Tableland type, Loess Hill type, and Transitional Form between Sand and Loess type), whereas there were both lower and higher values for P-N terrain pattern scales in all loess landforms in the longitudinal direction. The P-N terrain pattern alsoclearly presented anisotropy, suggesting that gully networks in the main direction were well-developed while others were relatively undeveloped. In addition, the relationships between the first scales and controlling factors(i.e., gully density, nibble degree, watershed area, mean watershed slope, NDVI, precipitation, loess thickness, and loess landforms) revealed that the first scales are primarily controlled by watershed area and loess landforms. This may indicate that the current spatial pattern of P-N terrains is characterized by internal force. In selecting suitable study areas in China' Loess Plateau, it is crucial to understand four control variables: the spatial scale of the P-N terrain pattern, the watershed area, the main direction of the watershed, and the loess landforms.
基金supported by the National Natural Science Foundation of China (Grant No. 41561004)the Forestry Industry Research Special Funds for Public Welfare Projects of China (Grant No. 21404402-2)the Scientific and Technological Innovation Talent Project of Yunnan Province (Grant No. 2014HC014)
文摘Local temperature changes in mountain areas are significantly affected by the uplifted mountain terrains. Understanding how temperature increase with mountain terrains is an important component in accurately modeling the spatial distribution of temperature. The study, after minimizing the effect of elevation and latitude, quantitatively simulated the temperature increase in the uplifted mountain terrains, described the characteristics in the spatial distribution of warming areas with different magnitudes, and identified the correlated indices of mountain bodies for warming. Selecting Yunnan Province in southwest China as the study area, we simulated the warming field on a baseline surface at the average elevation of 2000 m and average latitude of 24.96°. The results indicated that the warming magnitudes in different local areas varied with the change in the spatial locations, and the warming process concentrated in the mountainous regions. Throughout the entire study area, the warming field presented a general pattern of three terraces from the regions of high mountains to middle mountains and then low mountains. The areasof high warming magnitude mainly surrounded large mountain bodies and were distributed on the upper part. The areas of low warming magnitude clustered in the valleys and basins of the middle mountain region, mostly on the lower part of the large mountain bodies and its branches. The areas with zero warming magnitude occurred in the low mountains and broad valleys, which were distributed largely on the lower parts of the middle mountains and in most of the valleys. Quantified sampling analysis demonstrated good positive correlation between the warming magnitudes in uplifted mountain terrains and the volume index of the mountain body, as well as elevation difference, with the coefficients corresponding to 0.82 and 0.91, respectively.
基金supported by the National Natural Science Foundation of China(Nos.51208466 and 51238011)the Science and Technology Research Program of Chinese Ministry of Housing and Urban-Rural Development(No.2014R2-036)+2 种基金the Humanities and Social Sciences Research Foundation of the Ministry of Education(No.17YJAZH136)the Natural Science Foundation of Zhejiang Province(No.LY16E0 80011)the Social Sciences Planning Project of Zhejiang Province(No.12JCSH02YB),China
文摘The effect of wind environment is becoming increasingly important in analyzing and selecting sites for better naturalventilation of residential buildings, external comfort, and pollution dispersion. The mainpurpose of this study was to develop a setof methods for wind environment assessment in coastal concave terrains. This set of methods can be used to provide quantifiableindicators of preferable wind conditions and help site analysis. Firstly, a total of 20 types of coastal bays with concave terrains inEast Asia were characterized to find ideal locations. The selected areas were divided into five categories according to the mainterrain features. Then a sample database for the concave terrains was compiled for modelling comparisons. Secondly, a number ofkey wind variables were identified. Computational fluid dynamics （CFD） models of the typical coastal concave terrains identifiedas a result of the study were created, and the local wind environments were simulated with input from geographic informationsystem （GIS） and statistic package for social science （SPSS） analysis. A measure of wind suitability was proposed that takes windvelocity and wind direction into account using GIS. Finally, SPSS was used to find the relationship between wind suitability andkey terrain factors. The results showed that wind suitability was significantly associated with terrain factors, especially altitude.The results suggest that residential building sites should be selected such that their bay openings face the direction of the prevailingwind and that the opposite direction should be avoided.
文摘The classification of thematic mapper imagery in areas with strong topographic variations has proven problematic in the past using a single classifier, due to the changing sun illumination geometry. This often results in the phenomena of identical object with dissimilar spectrum and different objects with similar spectrum. In this paper, an integrated classification method that combines a decision tree with slope data, tasseled cap transformation indices and maximum likelihood classifier is introduced, to find an optimal classification method for thematic mapper imagery of plain and highland terrains. A Landsat 7 ETM+ image acquired over Hangzhou Bay, in eastern China was used to test the method. The results indicate that the performance of the inte- grated classifier is acceptably good in comparison with that of the existing most widely used maximum likelihood classifier. The integrated classifier depends on hypsography (variation in topography) and the characteristics of ground truth objects (plant and soil). It can greatly reduce the influence of the homogeneous spectrum caused by topographic variation. This integrated classifier might potentially be one of the most accurate classifiers and valuable tool for land cover and land use mapping of plain and highland terrains.
基金The Science and Technology Support Program of Jiangsu Province(No.BE2014133)the Prospective Joint Research Program of Jiangsu Province(No.BY2014127-01)
文摘In order to evaluate the impact of off-road terrains on the ride comfort of construction vehicles,a nonlinear dynamic model of the construction vehicles interacting with the terrain deformations is established based on Matlab/Simulink software.The weighted root mean square(RMS)acceleration responses and the power spectral density(PSD)acceleration responses of the driver s seat heave,the pitch and roll angle of the cab in the low-frequency region are chosen as objective functions under different operation conditions of the vehicle.The results show that the impact of off-road terrains on the driver s ride comfort and health is clear under various conditions of deformable terrains and range of vehicle velocities.In particular,the driver s ride comfort is greatly affected by a soil terrain while the comfortable shake of the driver is strongly affected by a sand terrain.In addition,when the vehicle travels on a poor soil terrain in the frequency range below 4 Hz,more resonance peaks of acceleration PSD responses occurred than that on a rigid road of ISO 2631-1 level C.Thus,the driver s health is significantly affected by the deformable terrain in a low-frequency range.
文摘In Pakistan,the solar analogue has been addressed but its surface geographical parameterization has given least attention.Inappropriate density of stations and their spatial coverage particularly in difficult peripheral national territories,little or no solar radiation data,non-satisfactory sunshine hours data,and low quality of ground observed cloud cover data create a situation in which the spatial modeling of Extraterrestrial Solar Radiation(ESR) and its ground parameterization got sufficient scope.The Digital Elevation Model (DEM) input into Geographic Information System (GIS) is a compatible tool to demonstrate the spatial distribution of ESR over the rugged terrains of the study domain.For the first time,distributed modeling of ESR is done over the rugged terrains of Pakistan,based on DEM and ArcGIS..Results clearly depict that the complex landforms profoundly disrupt the zonal distribution of ESR in Pakistan.The screening impact of topography is higher on spatial distribution of ESR in winter and considerably low in summer.The combined effect of topography and latitude is obvious.Hence,the model was further testified by plotting Rb (ratio of ESR quantity over rugged terrain against plane surface) against azimuth at different latitudes with different angled slopes.The results clearly support the strong screening effect of rugged terrain through out the country especially in Himalayas,Karakoram and Hindukush (HKH),western border mountains and Balochistan Plateau.This model can be instrumental as baseline geospatial information for scientific investigations in Pakistan,where substantial fraction of national population is living in mountainous regions.
文摘The major results about magnetic petrology of Archearn high grade terrains in the world are reviewed in this article, focusing on the relationship between rock magnetism and deformation, and metamorphism and intensity of magnetization of the lower continental crust. The important problems about the magnetic study of rocks for high grade terrains are advanced.
文摘The research was carried out in Dar es Salaam’s Makongo and Goba neighbourhoods using an exploratory method covering 200 questionnaires,100 for Goba and 100 for Makongo respectively.There were two significant issues observed:To begin,data from 2003 to 2017 reveal a large increase in urbanisation in both locations.Furthermore,urbanisation led to an increase in hard surface areas,which,according to the analysis,contributed to an increase in surface runoff,which had detrimental consequences for hilly residential settlements,resulting in downstream floods,building destruction,and loss of life and properties.Few residents were aware of water harvesting methods as a technique to deal with surface runoff,but they were not aware that they might be used to harvest water for future use.Policy to harvest,retain and use rainwater is recommended,whereby each plot owner should contain water from his/her plot by harvesting,collecting and retaining it for home use such as farming,fish ponds and other uses.
基金supported by the National Natural Science Foundation of China(Nos.61373137,61572260,61373017,61373139,and 61572261)the Major Program of Jiangsu Higher Education Institutions(No.14KJA520002)Scientific&Technological Support Project of Jiangsu(No.BE2015702)
文摘Coverage is an important issue in the area of wireless sensor networks, which reflects the monitoring quality of the sensor networks in scenes. Most sensor coverage research focuses on the ideal two-dimensional （2-D） plane and full three-dimensional （3-D） space. However, in many real-world applications, the target field is a 3-D complex surface, which makes conventional methods unsuitable. In this paper, we study the coverage problem in directional sensor networks for complex 3-D terrains, and design a new surface coverage algorithm. Based on a 3-D directional sensing model of nodes, this algorithm employs grid division, simulated annealing, and local optimum ideas to improve the area coverage ratio by optimizing the position coordinates and the deviation angles of the nodes, which results in coverage enhancement for complex 3-D terrains. We also conduct extensive simulations to evaluate the performance of our algorithms.
文摘Terrain Aided Navigation(TAN)technology has become increasingly important due to its effectiveness in environments where Global Positioning System(GPS)is unavailable.In recent years,TAN systems have been extensively researched for both aerial and underwater navigation applications.However,many TAN systems that rely on recursive Unmanned Aerial Vehicle(UAV)position estimation methods,such as Extended Kalman Filters(EKF),often face challenges with divergence and instability,particularly in highly non-linear systems.To address these issues,this paper proposes and investigates a hybrid two-stage TAN positioning system for UAVs that utilizes Particle Filter.To enhance the system’s robustness against uncertainties caused by noise and to estimate additional system states,a Fuzzy Particle Filter(FPF)is employed in the first stage.This approach introduces a novel terrain composite feature that enables a fuzzy expert system to analyze terrain non-linearities and dynamically adjust the number of particles in real-time.This design allows the UAV to be efficiently localized in GPS-denied environments while also reducing the computational complexity of the particle filter in real-time applications.In the second stage,an Error State Kalman Filter(ESKF)is implemented to estimate the UAV’s altitude.The ESKF is chosen over the conventional EKF method because it is more suitable for non-linear systems.Simulation results demonstrate that the proposed fuzzy-based terrain composite method achieves high positional accuracy while reducing computational time and memory usage.
基金supported by the National Natural Science Foundation of China(Grant No.41771423)the Natural Science Foundation of Fujian Province(Grant No.2023J01421).
文摘Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion.Quantitative analyses on loess landform have been employed from various perspectives.Peak intervisibility can provide the potential topographic information implied in the visual connectivity of peaks,however,its application in loess landform analysis remains unexplored.In this study,the interwoven sightlines among peaks,representing peak intervisibility,were extracted from the digital elevation model and simulated into a peak intervisibility network(PIN).Nine indices were proposed to quantify the PIN.Through a case study in Northern Shaanxi,China,three tasks were conducted,including,landform interpretation,spatial pattern mining,and landform classification.The main findings are as follows:(1)PIN responds to terrain morphology and is beneficial for loess landform interpretation.(2)The spatial patterns of PIN indices are heterogeneous and strongly coupled with the terrain morphologies,showing anisotropy and autocorrelation in spatial variations.(3)Using the light gradient boost machine classifier,the PIN index-based classification reaches a mean accuracy of 86.09%,an overall accuracy of 86%and a kappa coefficient of 0.84.These findings shed light on the applicability of PIN in loess landform analysis.Peak intervisibility not only enriches the theories and methodologies of relation-based digital terrain analysis,but also enhances our comprehension of loess landform genesis,morphology,distribution,and evolution.
基金Supported by the Foundation Enhancement Program Project"Key Technologies for Analytical Traceability and Numerical Modeling of Fluctuations in the Middle and Upper Atmosphere"(2022-JCJQ-JJ-0882).
文摘Typhoons,as strong convective systems,can excite multi-scale atmospheric gravity waves that travel long distances,and play an important role in momentum and energy transmission between the middle and upper atmosphere.In this paper,the research progress in the observation techniques,generation mechanism and propagation characteristics of typhoon-induced gravity waves were systematically reviewed.These studies show that based on the combined application of ground-based and space-based observation(sounding balloons,airglow imaging,and satellite remote sensing)and reanalysis data(such as ERA5),with the aid of ray tracing theory and numerical simulation technology,the mechanism of typhoon induced gravity waves and its dynamic characteristics in the middle and upper atmosphere have been better revealed.At present,there are still some insufficiencies in the fields of propagation path tracking of gravity waves,terrain multi-scale effect modeling and parameterization of inertial gravity waves,which need to be further studied in the future.
文摘With the advancement of deep learning in the automotive domain,more and more researchers are focusing on autonomous driving.Among these tasks,free space detection is particularly crucial.Currently,many model-based approaches have achieved autonomous driving on well-structured urban roads,but these efforts primarily focus on urban road environments.In contrast,there are fewer deep learningmethods specifically designed for off-road traversable area detection,and their effectiveness is not yet satisfactory.This is because detecting traversable areas in complex outdoor environments poses significant challenges,and current methods often rely on single-image inputs,which do not align with contemporary multimodal approaches.Therefore,in this study,we propose a CFH-Net model for off-road traversable area detection.This model employs a Transformer architecture to enhance its capability of capturing global information.For multimodal feature extraction and fusion,we integrate the CM-FRM module for feature extraction and introduce the novel FFX module for feature fusion,thereby improving the perception capability of autonomous vehicles on unstructured roads.To address upsampling,we propose a new convolution precorrection method to reduce model parameters and computational complexity while enhancing the model’s ability to capture complex features.Finally,we conducted experiments on the ORFD off-road dataset and achieved outstanding results.
文摘Geomorphometric modeling and mapping of Antarctic oases are promising for obtaining new quantitative knowledge about the topography of these unique landscapes and for the further use of morphometric information in Antarctic research.Within the framework of a project to create a thematic physical-geographical scientific reference geomorphometric atlas of ice-free areas of Antarctica,we performed geomorphometric modeling and mapping of the Bunger Hills(Knox Coast,Wilkes Land,East Antarctica),one of the largest Antarctic oases.By processing a fragment of the Reference Elevation Model of Antarctica(REMA)covering the Bunger Hills and adjacent glaciers,we created,for the first time,a series of 37 medium-to large-scale maps of nine of the most scientifically important morphometric variables(i.e.,slope gradient,slope aspect,vertical curvature,horizontal curvature,maximal curvature,minimal curvature,catchment area,topographic wetness index,and stream power index).The morphometric maps describe the topography of the Bunger Hills in a quantitative,rigorous,and reproducible manner.New morphometric data can be useful for further geological,geomorphological,glaciological,ecological,and hydrological studies of this Antarctic oasis.
基金financially supported by the National Natural Science Foundation of China(Grant No.42361002)the Fund of Ningxia Hui Autonomous Region(Grant No.2022AAC03665).
文摘Tafoni are globally developed on cliffy slopes,and many of them are favorable places for the preservation of stone historical relics.However,the characteristics and formation processes of tafoni in the Loess Plateau are yet to be understood.This paper studied the features of the tafoni on conglomerate slopes in Huoshizhai National Geopark of Ningxia Hui Autonomous Region and discussed its formation processes by field investigation and morphometry,insitu relative humidity(RH)measurement,salt chemistry and X-ray fluorescence spectrometer(XRF)experiments of 24 samples.The bedrock of the tafoni is dominated by reddish fluvial conglomerates of the Lower Cretaceous Heshangpu Formation with abundant chemically unstable components including feldspars,lithic fragments,and calcite cements.The RH values vary from 5%to 100%,but the backwalls of the tafoni have higher RH values than outer surfaces.The more moisture on the backwalls is possibly generated by water influx from the rock interior,resulting in more salt precipitation on the backwalls.As a result,the backwalls have been subject to predominant salt weathering.The dominant salts involved in salt weathering are probably derived from the dissolution of the salt interbeds in the basin,although the chemical dissolution of the unstable components such as feldspars,lithic fragments,and calcite cements might have produced small amounts of salts.The salt types dominantly include nitrates,sulfates,and halite.In the progression of tafoni,the moisture maintenance on the backwalls gives rise to the accretion of salts,which in turn enhance the weathering rates of the backwalls.As a result,the volumes of the tafoni have become enlarged owing to inward growth and coalescence of adjacent smaller ones.
基金funded by the Yunnan Provincial Basic Research Joint Special Fund Project(2019FH001(-052))Cangshan Mountain Synthetic Scientific Expeditions Fund.
文摘The Hengduan Mountains,situated on the southeastern edge of the Qinghai-Tibet Plateau,are the longest and widest north-south-oriented mountain range in China,exerting a significant influence on the ecological and geographical pattern.Understanding the topographic and geomorphological characteristics of the Hengduan Mountains is fundamental and crucial for research in related fields such as ecology,geography,and sustainability.In this study,Digital Elevation Model(DEM)data were utilized to extract and analyze the topography and geomorphology(TG)pattern.TG maps have been developed to quantitatively classify the TG types in the Hengduan Mountains by combining the five factors of elevation,slope,aspect,relief and landform.The spatial distribution and quantitative characteristics of these factors were mapped and investigated using geographic information systems.The results revealed that:(1)The Hengduan Mountains exhibit an elongated north-south distribution,with an average elevation of approximately 3746 m,an average slope of around 25°,and an average relief of about 266 m.(2)The Hengduan Mountains display significant elevation differences,with an overall high elevation,characterized by a trend of lower elevation in the east and higher elevation in the west,as well as irregular orientations of various aspects.(3)The 19 landform types were identified,the landform types of the Hengduan Mountains are primarily composed of low-relief high-mountains(42.0618%),low-relief mid-mountains(22.4624%),and high-elevation hills(20.5839%).The results of the study can provide data and information support for the ecology,environmental protection and sustainable development of the Hengduan Mountains.
基金supported by the National Natural Science Foundation of China(No.32271876)the Research on Key Technologies of Intelligent Monitoring and Carbon Sink Metering of Forest Resources in Fujian Province(No.2022FKJ03)the Science and Technology Innovation Project of Fujian Agriculture and Forestry University(No.KFB23172A,KFB23173A).
文摘Unmanned aerial vehicle light detection and ranging(UAV–LiDAR)is a new method for collecting understory terrain data.The high estimation accuracy of understory terrain is crucial for accurate tree height measurement and forest resource surveys.The UAV–LiDAR flight altitude and forest canopy cover significantly impact the accuracy of understory terrain estimation.However,since no research examined their combined effects,we aimed to investigate this relationship.This will help optimize UAV–LiDAR flight parameters for understory terrain estimation and forest surveys across various canopy cover.This study analyzed the impacts of three flight altitudes and three canopy cover on the estimation accuracy of understory terrain.The results showed that when canopy cover exceeded a specific value,UAV–LiDAR flight altitudes significantly affected understory terrain estimation.Given a forest canopy cover,the reduction in ground point coverage increased significantly as the flight altitude increased;given a flight altitude,the higher the canopy cover,the more significant the reduction in ground point coverage.In forests with a canopy cover≥0.9,there were substantial differences in the accuracies of understory digital elevation models(DEMs)generated using UAV–LiDAR at different flight altitudes.For forests with a canopy cover<0.9,the mean absolute error(MAE)of understory DEMs from UAV–LiDAR at different flight altitudes was≤0.17 m and the root mean square error(RMSE)was≤0.24 m.However,for forests with a canopy cover≥0.9,the UAV–LiDAR flight altitude significantly affected the accuracy of understory DEMs.At the same flight altitude,the MAE and RMSE of the estimated elevation for forests with a canopy cover≥0.9 were approximately twice those of the estimated elevation for forests with a canopy cover<0.9.In forests with low canopy cover,it is possible to improve data collection efficiency by selecting a higher flight altitude.However,UAV–LiDAR flight altitudes significantly affected understory terrain estimation in forests with high canopy cover,it is essential to adopt terrain-following flight modes,reduce flight altitudes,and maintain a consistent flight altitude during longterm monitoring in high canopy cover forests.
