In 2025,I had the honor of delivering keynote speeches at the conferences of the International Society for Diet and Activity Methods in Toronto,Canada,and the International Society of Behavioural Nutrition and Physica...In 2025,I had the honor of delivering keynote speeches at the conferences of the International Society for Diet and Activity Methods in Toronto,Canada,and the International Society of Behavioural Nutrition and Physical Activity in Auckland,Aotearoa,New Zealand.These opportunities prompted deep reflection on scientific research in general,and on physical activity and health research specifically.展开更多
Accurate digital terrain models(DTMs)are essential for a wide range of geospatial and environmental applications,yet their derivation in forested regions remains a significant challenge.Existing global DTMs,typically ...Accurate digital terrain models(DTMs)are essential for a wide range of geospatial and environmental applications,yet their derivation in forested regions remains a significant challenge.Existing global DTMs,typically generated from satellite stereo photogrammetry or interferometric synthetic aperture radar(InSAR),fail to accurately capture understory terrain due to limited penetration capabilities,resulting in elevation overestimation in densely vegetated areas.While airborne light detection and ranging(LiDAR)can provide high-accuracy DTMs,its limited spatial coverage and high acquisition cost hinder large-scale applications.Thus,there is an urgent need for a scalable and cost-effective approach to extract DTMs directly from satellite-derived digital surface models(DSMs).In this study,we propose a simple,interpretable understory terrain extraction method that utilizes canopy height data from Global Ecosystem Dynamics Investigation(GEDI)and Ice,Cloud,and Land Elevation Satellite-2(ICESat-2)to construct a tree height surface model,which is then subtracted from the stereo-derived DSM to generate the final DTM.By directly incorporating LiDAR constraints,the method avoids error propagation from multiple heterogeneous datasets and reduces reliance on ancillary inputs,ensuring ease of implementation and broad applicability.In contrast to machine learning-based terrain modeling methods,which are often prone to overfitting and data bias,the proposed approach is simple,interpretable,and robust across diverse forested landscapes.The accuracy of the resulting DTM was validated against airborne LiDAR reference data and compared with both the Copernicus Digital Elevation Model(DEM)and the forest and buildings removed DEM(FABDEM),a global bare-earth elevation model corrected for vegetation bias.The results indicate that the proposed DTM consistently outperforms the Copernicus DEM(CopDEM)and achieves accuracy comparable to FABDEM.In addition,its finer spatial resolution of 1 m,compared to the 30 m resolution of FABDEM,allows for more detailed terrain representation and better capture of fine-scale variation.This advantage is most pronounced in gently to moderately sloped areas,where the proposed DTM shows clearly higher accuracy than both the CopDEM and FABDEM.The results confirm that high-resolution DTMs can be effectively extracted from DSMs using spaceborne LiDAR constraints,offering a scalable solution for terrain modeling in forested environments where airborne LiDAR is unavailable.To illustrate the potential utility of the proposed DTM,we applied it to a fire risk mapping application based on topographic parameters such as slope,aspect,and elevation.This case highlights how improved terrain representation can support geospatial hazard assessments.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
Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry.Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and acc...Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry.Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and accumulate to form slug flow, so it is necessary to remove the accumulated liquid by gas purging. In this paper, experiment is carried out in hilly terrain pipelines. Three flow patterns of stratified flow, slug flow and stratified entrained flow are observed. The process of gas purging accumulated liquid is divided into four stages, namely liquid accumulation, liquid rising, continuous outflow and tail outflow. At the same time, the flow pattern maps of each stage are drawn. The pressure drop signal is analyzed in time domain and frequency domain, and the contour map of pressure drop distribution is drawn. It is found that the ratio of range to average value can well distinguish the occurrence range of each flow pattern.Based on visualization, the transition process of slug flow to stratified flow and stratified entrained flow is studied, and the transition boundary prediction model is established. An image processing method is proposed to convert the image signal into a similarity curve, and PSD analysis is performed to calculate the slug frequency. The normal distribution is used to fit the slug frequency, and the predicted correlation is in good agreement with the experimental data.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
Accurate estimation of understory terrain has significant scientific importance for maintaining ecosystem balance and biodiversity conservation.Addressing the issue of inadequate representation of spatial heterogeneit...Accurate estimation of understory terrain has significant scientific importance for maintaining ecosystem balance and biodiversity conservation.Addressing the issue of inadequate representation of spatial heterogeneity when traditional forest topographic inversion methods consider the entire forest as the inversion unit,this study pro⁃poses a differentiated modeling approach to forest types based on refined land cover classification.Taking Puerto Ri⁃co and Maryland as study areas,a multi-dimensional feature system is constructed by integrating multi-source re⁃mote sensing data:ICESat-2 spaceborne LiDAR is used to obtain benchmark values for understory terrain,topo⁃graphic factors such as slope and aspect are extracted based on SRTM data,and vegetation cover characteristics are analyzed using Landsat-8 multispectral imagery.This study incorporates forest type as a classification modeling con⁃dition and applies the random forest algorithm to build differentiated topographic inversion models.Experimental re⁃sults indicate that,compared to traditional whole-area modeling methods(RMSE=5.06 m),forest type-based classi⁃fication modeling significantly improves the accuracy of understory terrain estimation(RMSE=2.94 m),validating the effectiveness of spatial heterogeneity modeling.Further sensitivity analysis reveals that canopy structure parame⁃ters(with RMSE variation reaching 4.11 m)exert a stronger regulatory effect on estimation accuracy compared to forest cover,providing important theoretical support for optimizing remote sensing models of forest topography.展开更多
Background Three-dimensional terrain models are essential in domains such as video game development and film production.Because surface color is often correlated with terrain geometry,capturing this relationship is cr...Background Three-dimensional terrain models are essential in domains such as video game development and film production.Because surface color is often correlated with terrain geometry,capturing this relationship is critical for generating realistic results.However,most existing methods synthesize either a heightmap or a texture without adequately modeling their inherent correlation.Methods We propose a method that jointly generates terrain heightmaps and textures using a latent diffusion model.First,we train the model in an unsupervised manner to randomly generate paired heightmaps and textures.Then,we perform supervised learning on an external adapter to enable user control via hand-drawn sketches.Results Experiments demonstrate that our approach supports intuitive terrain generation while preserving the correlation between heightmaps and textures.Conclusion Our method outperforms the two-stage and GAN-based baselines by ensuring structural coherence,in which textures naturally align with geometry,successfully accommodating both realistic landscapes and extreme user-defined shapes.展开更多
The Light Detection and Ranging(LiDAR)data analysis method has emerged as a powerful and versatile tool for characterizing atmospheric conditions and modeling light propagation through various media.In the context of ...The Light Detection and Ranging(LiDAR)data analysis method has emerged as a powerful and versatile tool for characterizing atmospheric conditions and modeling light propagation through various media.In the context of renewable energy,particularly wind energy,LiDAR is increasingly utilized to analyze wind flow,turbine wake effects,and turbulence in complex terrains.This study focuses on advancing LiDAR data interpretation through the development and application of the LiDAR Statistical Barnes Objective Analysis(LiSBOA)method.LiSBOA enhances the capacity of scanning LiDAR systems by enabling more precise optimization of scan configurations and improving the retrieval of wind statistics across Cartesian grids.Unlike conventional approaches,LiSBOA offers fine-grained control over azimuthal resolution and spatial filtering,which allows for the detailed reconstruction of wind fields and turbulence structures.These capabilities are crucial for accurately simulating wind turbine wakes and power capture,particularly in environments with variable atmospheric stability and complex topography.Field deployments and comparative assessments against traditional meteorological mast data demonstrate the effectiveness of LiSBOA.The method reduces wind velocity estimation errors to within 3%and increases the accuracy of turbulence intensity measurements by over 4%.Such improvements are significant for enhancing wind resource assessment,optimizing turbine placement,and refining control strategies for operational turbines.LiSBOA represents a robust advancement in LiDAR data processing for wind energy applications.By addressing limitations in spatial resolution and measurement uncertainty,it supports more reliable modeling of wake interactions and flow variability.This work contributes to improving the efficiency and reliability of wind energy systems through advanced remote sensing and statistical analysis techniques.展开更多
Agricultural terraces are significant for food provision,environmental stability and sustainable resource management.However,the spatiotemporal evolution of terraces and their influence on food productivity in mountai...Agricultural terraces are significant for food provision,environmental stability and sustainable resource management.However,the spatiotemporal evolution of terraces and their influence on food productivity in mountainous landscapes remain poorly understood.Taking the Chinese Loess Plateau(LP)as an example,this study conducted multitemporal mapping of terraces and sloping croplands over three decades(1990-2020),systematically assessing their impacts on food output through terrain gradient analysis.The results indicated that:(1)the terraced area expanded in the past 30 years,particularly across steeper terrain gradients(third to fifth gradients);(2)sloping croplands predominantly occupied gentle slopes(first to second gradients),exhibiting area reduction correlating with urbanization processes;(3)the food provision increased extensively,with yield decreasing from southeast to northwest and regions of high yielding mainly in terraced fields;(4)over time,the variation of food provision correlated positively with the area of sloping cropland at low gradients,while at higher gradients,the expansion of terraces dominated the increase in food provision;(5)spatial clustering analysis revealed significant food productivity associated with high-density terrace distribution across steeper slope gradients.Low yields could be attributed to improper terrace management.This study clarified the impact of long-term terrace patterns on food provision and offered large-scale perspectives for terrace-based agriculture to enhance food security.Furthermore,the findings underscore the imperative of integrated land management in topographically complex regions,informing evidence-based policymaking for rational allocation and optimal utilization of terrace resources.展开更多
Terrain and geological formation are crucial natural environmental factors that constrain land use and land cover changes.Studying their regulatory role in regional land use and land cover changes is significant for g...Terrain and geological formation are crucial natural environmental factors that constrain land use and land cover changes.Studying their regulatory role in regional land use and land cover changes is significant for guiding regional land resource management.Taking the Danjiang River Basin in the Qinling Mountains of China as an example,this paper incorporates terrain(elevation,slope,and aspect)factors and geological formation to comprehensively analyse the differentiation characteristics of land use spatial patterns based on the examination of land use changes in 2000,2010,and 2020.Moreover,the geographical detector is employed to compare and analyse the effect of each factor on the spatial heterogeneity of land use.The results show that:(1)From 2000 to 2020,the areas of arable land and forestland in the Danjiang River Basin decreased while the areas of grassland,water areas,construction land,and unused land continuously increased.The comprehensive land use dynamics index was+0.09%,indicating a generally low level of land development.(2)Differences in the natural environmental factors of terrain and geological formation have a significant controlling effect on the spatial heterogeneity of land use.Specifically,there are notable differences in the advantageous distribution characteristics of various land use types across different levels of influencing factors.(3)The factor detection results reveal that geological formation has the strongest influence on the spatial heterogeneity of land use,followed by elevation and slope while aspect has the weakest influence.After the interaction among the factors,they nonlinearly enhance the explanation of spatial heterogeneity in land use.Overall,the influence of geological formation on the spatial heterogeneity of land use is greater than that of terrain factors.This study provides new geological evidence for natural resource management departments to conduct regional spatial planning,ecological and environmental protection and restoration,and land structure optimization and adjustment.展开更多
Accurate reconstruction of understory terrain is essential for environmental monitoring and resource management.This study integrates 1:10,000 Digital Elevation Model,Global Ecosystem Dynamics Investigation(GEDI),and ...Accurate reconstruction of understory terrain is essential for environmental monitoring and resource management.This study integrates 1:10,000 Digital Elevation Model,Global Ecosystem Dynamics Investigation(GEDI),and AW3D30 Digital Surface Model data,combined with three machine learning algorithms—Random Forest(RF),Back Propagation Neural Network(BPNN),and Extreme Gradient Boosting(XGBoost)—to evaluate the performance of canopy height inversion and understory terrain reconstruction.The analysis emphasizes the impact of topographic and vegetation-related factors on model accuracy.Results reveal that slope is the most influential variable,contributing three to five times more to model performance than other features.In low-slope areas,understory terrain tends to be underestimated,whereas high-slope areas often result in overestimation.Moreover,the Normalized Difference Vegetation Index(NDVI)and land cover types,particularly forests and grasslands,significantly affect prediction accuracy,with model performance showing heightened sensitivity to vegetation characteristics in these regions.Among the models tested,XGBoost demonstrated superior performance,achieving a canopy height bias of-0.06 m,a root mean square error(RMSE)of 4.69 m for canopy height,and an RMSE of 9.82 m for understory terrain.Its ability to capture complex nonlinear relationships and handle high-dimensional data underlines its robustness.While the RF model exhibited strong stability and resistance to noise,its accuracy lagged slightly behind XGBoost.The BPNN model,by contrast,struggled in areas with complex terrain.This study offers valuable insights into feature selection and optimization in remote sensing applications,providing a reference framework for enhancing the accuracy and efficiency of environmental monitoring practices.展开更多
Large-scale urban land expansion in mountainous and hilly areas(UEMH)has significantly altered the terrain in many Chinese cities,leading to various environmental and urban challenges.Despite its importance,there is l...Large-scale urban land expansion in mountainous and hilly areas(UEMH)has significantly altered the terrain in many Chinese cities,leading to various environmental and urban challenges.Despite its importance,there is limited nation-scale research that reveals the amount and the spatial variations of UEMH-induced terrain alteration.This research integrates the Global Annual Urban Dynamics dataset,the Global Basic Landform Unit dataset,the TanDEM-X DEM Change Map(DCM)dataset,Baidu Points-of-Interest(POI),and other auxiliary datasets to conduct a comprehensive analysis of terrain alteration induced by UEMH in China from 2012 to 2020.The results indicate that the country-wide UEMH-induced terrain alteration reached approximately 13 billion m^(3),which is about 100 times the volume of Hangzhou West Lake,and terrain alteration volume in over 300 counties exceeded 10 million m^(3).The Southwest and Southeast regions,which are ecologically sensitive and critical,feature the greatest alteration in terms of area and volume.The most significant terrain alteration in terms of intensity is observed in the Southwest and Hengduan Mountain Area.Additionally,there are significant spatial variations in the contributions of different urban functional zones to terrain alteration.Our findings indicate that urban land expansion in mountains and hills has significantly altered terrain in some regions of China,necessitating customized urban planning strategies for better managing mountainous urban land expansion and governance policies to address the geological,ecological,and urban development challenges.展开更多
In order to slove a realistic test problem of TF/TA algorithm, it is necessary to make a discrete terrain model. The model has adjustable roughness parameters so as to test the optimization procedure for different typ...In order to slove a realistic test problem of TF/TA algorithm, it is necessary to make a discrete terrain model. The model has adjustable roughness parameters so as to test the optimization procedure for different types of terrain. In this paper, an algorithm to generate random terrain data is given.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
[Objective]The aim was to study the distribution characteristics of terrain reflected radiation in Fujian Province.[Method]Based on solar radiation data,digital elevation model(DEM)and surface meteorological observati...[Objective]The aim was to study the distribution characteristics of terrain reflected radiation in Fujian Province.[Method]Based on solar radiation data,digital elevation model(DEM)and surface meteorological observation data in Fujian Province,plus surface albedo obtained by using remote sensing inversion method,the distribution of terrain reflected radiation in Fujian Province from 1988 to 2007 was simulated,and then its temporal and spatial distribution characteristics was studied.[Result]The simulation results of terrain reflected radiation in Fujian Province was credible.Terrain reflected radiation in Fujian Province was the highest in July(about 160 MJ/m2)and lowest in January(about 60 MJ/m2),and it was obviously higher from May to August compared with other months,while the order of terrain reflected radiation in four seasons was summer>spring>autumn>winter,and complex terrain affected the distribution of terrain reflected radiation greatly,especially in autumn and winter when sun elevation angle was small.In addition,terrain reflected radiation in most areas of Fujian Province was below 100 MJ/m2,and it was high in Ningde,Sanming and Nanping City in northern Fujian,while the maximum value(630 MJ/m2)could be found in Dong’an Island in Xiapu County in Ningde City and had good utilization value.[Conclusion]The study could provide theoretical foundation for the development and utilization of solar energy resources under complex terrain in China.展开更多
A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics proc...A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics process, and by means of reducing the height of Yunnan-Guizhou Plateau and cutting off the middle-east of the Yunnan-Guizhou Plateau on the simulated tests, the question as how the ladder terrain on the west of Yunnan-Guizhou Plateau impact on the rainstorm of Guizhou was studied. The analysis results showed that the second ladder terrain of Yunnan-Guizhou Plateau only affected the development of convective clouds on its backward position,and hardly affected the rain on its upward. The whole terrain of the Yunnan-Guizhou Plateau had a distinct impact not only on the windward slope rainfall of the west of the plateau, but also on the rainfall distribution, intensity and continuing time of the convective clouds on the middle-east of the plateau.展开更多
To improve the navigation accuracy of an autonomous underwater vehicle （AUV）, a novel terrain passive integrated navigation system （TPINS） is presented. According to the characteristics of the underwater environme...To improve the navigation accuracy of an autonomous underwater vehicle （AUV）, a novel terrain passive integrated navigation system （TPINS） is presented. According to the characteristics of the underwater environment and AUV navigation requirements of low cost and high accuracy, a novel TPINS is designed with a configuration of the strapdown inertial navigation system （SINS）, the terrain reference navigation system （TRNS）, the Doppler velocity sonar （DVS）, the magnetic compass and the navigation computer utilizing the unscented Kalman filter （UKF） to fuse the navigation information from various navigation sensors. Linear filter equations for the extended Kalman filter （EKF）, nonlinear filter equations for the UKF and measurement equations of navigation sensors are addressed. It is indicated from the comparable simulation experiments of the EKF and the UKF that AUV navigation precision is improved substantially with the proposed sensors and the UKF when compared to the EKF. The TPINS designed with the proposed sensors and the UKF is effective in reducing AUV navigation position errors and improving the stability and precision of the AUV underwater integrated navigation.展开更多
To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwat...To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrainmatching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation（LSE） is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.展开更多
Digital terrain analysis(DTA)is one of the most important contents in the research of geographical information science(GIS).However,on the basis of the digital elevation model(DEM),many problems exist in the current r...Digital terrain analysis(DTA)is one of the most important contents in the research of geographical information science(GIS).However,on the basis of the digital elevation model(DEM),many problems exist in the current research of DTA in geomorphological studies.For instance,the current DTA research appears to be focused more on morphology,phenomenon,and modern surface rather than mechanism,process,and underlying terrain.The current DTA research needs to be urgently transformed from the study of landform morphology to one focusing on landform process and mechanism.On this basis,this study summarizes the current research status of geomorphology-oriented DTA and systematically reviews and analyzes the research about the knowledge of geomorphological ontology,terrain modeling,terrain derivative calculation,and terrain analytical methods.With the help of DEM data,DTA research has the advantage of carrying out geomorphological studies from the perspective of surface morphology.However,the study of DTA has inherent defects in terms of data expression and analytic patterns.Thus,breakthroughs in basic theories and key technologies are necessary.Moreover,scholars need to realize that DTA research must be transformed from phenomenon to mechanism,from morphology to process,and from terrain to landform.At present,the research development of earth science has reached the critical stage in which the DTA research should focus more on geomorphological ontology.Consequently,this study proposes several prospects of geomorphology-oriented DTA from the aspects of value-added DEM data model,terrain derivatives and their spatial relations,and macro-terrain analysis.The study of DTA based on DEM is at a critical period along with the issue on whether the current GIS technology can truly support the development of geography.The research idea of geomorphology-oriented DTA is expected to be an important exploration and practice in the field of GIS.展开更多
Based on the estimating rule of the normal vector angles between two adjacent terrain units, we use the concept of terrain complexity factor to quantify the terrain complexity of DEM, and then the formula of terrain c...Based on the estimating rule of the normal vector angles between two adjacent terrain units, we use the concept of terrain complexity factor to quantify the terrain complexity of DEM, and then the formula of terrain complexity factor in Raster DEM and TIN DEM is deduced theoretically. In order to make clear how the terrain complexity factor ECF and the average elevation h affect the accuracy of DEM terrain representation RMSEEt, the formula of Gauss synthetical surface is applied to simulate several real terrain surfaces, each of which has different terrain complexity. Through the statistical analysis of linear regression in simula- tion data, the linear equation between accuracy of DEM terrain representation RMSEEt, terrain complexity factor ECF and the average elevation h is achieved. A new method is provided to estimate the accuracy of DEM terrain representation RMSEEt with a certain terrain complexity and it gives convincing theoretical evidence for DEM production and the corresponding error research in the future.展开更多
文摘In 2025,I had the honor of delivering keynote speeches at the conferences of the International Society for Diet and Activity Methods in Toronto,Canada,and the International Society of Behavioural Nutrition and Physical Activity in Auckland,Aotearoa,New Zealand.These opportunities prompted deep reflection on scientific research in general,and on physical activity and health research specifically.
基金supported by the National Key Research and Development Program of China(Nos.SQ2022YFB3900026 and 2022YFB3903305)supported by the Leading Talents of Guangdong Pearl River Talent Program(No.2021CX02S024)the Guangdong S&T programme(No.2024B1212050011).
文摘Accurate digital terrain models(DTMs)are essential for a wide range of geospatial and environmental applications,yet their derivation in forested regions remains a significant challenge.Existing global DTMs,typically generated from satellite stereo photogrammetry or interferometric synthetic aperture radar(InSAR),fail to accurately capture understory terrain due to limited penetration capabilities,resulting in elevation overestimation in densely vegetated areas.While airborne light detection and ranging(LiDAR)can provide high-accuracy DTMs,its limited spatial coverage and high acquisition cost hinder large-scale applications.Thus,there is an urgent need for a scalable and cost-effective approach to extract DTMs directly from satellite-derived digital surface models(DSMs).In this study,we propose a simple,interpretable understory terrain extraction method that utilizes canopy height data from Global Ecosystem Dynamics Investigation(GEDI)and Ice,Cloud,and Land Elevation Satellite-2(ICESat-2)to construct a tree height surface model,which is then subtracted from the stereo-derived DSM to generate the final DTM.By directly incorporating LiDAR constraints,the method avoids error propagation from multiple heterogeneous datasets and reduces reliance on ancillary inputs,ensuring ease of implementation and broad applicability.In contrast to machine learning-based terrain modeling methods,which are often prone to overfitting and data bias,the proposed approach is simple,interpretable,and robust across diverse forested landscapes.The accuracy of the resulting DTM was validated against airborne LiDAR reference data and compared with both the Copernicus Digital Elevation Model(DEM)and the forest and buildings removed DEM(FABDEM),a global bare-earth elevation model corrected for vegetation bias.The results indicate that the proposed DTM consistently outperforms the Copernicus DEM(CopDEM)and achieves accuracy comparable to FABDEM.In addition,its finer spatial resolution of 1 m,compared to the 30 m resolution of FABDEM,allows for more detailed terrain representation and better capture of fine-scale variation.This advantage is most pronounced in gently to moderately sloped areas,where the proposed DTM shows clearly higher accuracy than both the CopDEM and FABDEM.The results confirm that high-resolution DTMs can be effectively extracted from DSMs using spaceborne LiDAR constraints,offering a scalable solution for terrain modeling in forested environments where airborne LiDAR is unavailable.To illustrate the potential utility of the proposed DTM,we applied it to a fire risk mapping application based on topographic parameters such as slope,aspect,and elevation.This case highlights how improved terrain representation can support geospatial hazard assessments.
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.
基金supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.52488201)the National Natural Science Foundation of China(No.52422606).
文摘Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry.Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and accumulate to form slug flow, so it is necessary to remove the accumulated liquid by gas purging. In this paper, experiment is carried out in hilly terrain pipelines. Three flow patterns of stratified flow, slug flow and stratified entrained flow are observed. The process of gas purging accumulated liquid is divided into four stages, namely liquid accumulation, liquid rising, continuous outflow and tail outflow. At the same time, the flow pattern maps of each stage are drawn. The pressure drop signal is analyzed in time domain and frequency domain, and the contour map of pressure drop distribution is drawn. It is found that the ratio of range to average value can well distinguish the occurrence range of each flow pattern.Based on visualization, the transition process of slug flow to stratified flow and stratified entrained flow is studied, and the transition boundary prediction model is established. An image processing method is proposed to convert the image signal into a similarity curve, and PSD analysis is performed to calculate the slug frequency. The normal distribution is used to fit the slug frequency, and the predicted correlation is in good agreement with the experimental data.
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(42401488,42071351)the National Key Research and Development Program of China(2020YFA0608501,2017YFB0504204)+4 种基金the Liaoning Revitalization Talents Program(XLYC1802027)the Talent Recruited Program of the Chinese Academy of Science(Y938091)the Project Supported Discipline Innovation Team of the Liaoning Technical University(LNTU20TD-23)the Liaoning Province Doctoral Research Initiation Fund Program(2023-BS-202)the Basic Research Projects of Liaoning Department of Education(JYTQN2023202)。
文摘Accurate estimation of understory terrain has significant scientific importance for maintaining ecosystem balance and biodiversity conservation.Addressing the issue of inadequate representation of spatial heterogeneity when traditional forest topographic inversion methods consider the entire forest as the inversion unit,this study pro⁃poses a differentiated modeling approach to forest types based on refined land cover classification.Taking Puerto Ri⁃co and Maryland as study areas,a multi-dimensional feature system is constructed by integrating multi-source re⁃mote sensing data:ICESat-2 spaceborne LiDAR is used to obtain benchmark values for understory terrain,topo⁃graphic factors such as slope and aspect are extracted based on SRTM data,and vegetation cover characteristics are analyzed using Landsat-8 multispectral imagery.This study incorporates forest type as a classification modeling con⁃dition and applies the random forest algorithm to build differentiated topographic inversion models.Experimental re⁃sults indicate that,compared to traditional whole-area modeling methods(RMSE=5.06 m),forest type-based classi⁃fication modeling significantly improves the accuracy of understory terrain estimation(RMSE=2.94 m),validating the effectiveness of spatial heterogeneity modeling.Further sensitivity analysis reveals that canopy structure parame⁃ters(with RMSE variation reaching 4.11 m)exert a stronger regulatory effect on estimation accuracy compared to forest cover,providing important theoretical support for optimizing remote sensing models of forest topography.
文摘Background Three-dimensional terrain models are essential in domains such as video game development and film production.Because surface color is often correlated with terrain geometry,capturing this relationship is critical for generating realistic results.However,most existing methods synthesize either a heightmap or a texture without adequately modeling their inherent correlation.Methods We propose a method that jointly generates terrain heightmaps and textures using a latent diffusion model.First,we train the model in an unsupervised manner to randomly generate paired heightmaps and textures.Then,we perform supervised learning on an external adapter to enable user control via hand-drawn sketches.Results Experiments demonstrate that our approach supports intuitive terrain generation while preserving the correlation between heightmaps and textures.Conclusion Our method outperforms the two-stage and GAN-based baselines by ensuring structural coherence,in which textures naturally align with geometry,successfully accommodating both realistic landscapes and extreme user-defined shapes.
文摘The Light Detection and Ranging(LiDAR)data analysis method has emerged as a powerful and versatile tool for characterizing atmospheric conditions and modeling light propagation through various media.In the context of renewable energy,particularly wind energy,LiDAR is increasingly utilized to analyze wind flow,turbine wake effects,and turbulence in complex terrains.This study focuses on advancing LiDAR data interpretation through the development and application of the LiDAR Statistical Barnes Objective Analysis(LiSBOA)method.LiSBOA enhances the capacity of scanning LiDAR systems by enabling more precise optimization of scan configurations and improving the retrieval of wind statistics across Cartesian grids.Unlike conventional approaches,LiSBOA offers fine-grained control over azimuthal resolution and spatial filtering,which allows for the detailed reconstruction of wind fields and turbulence structures.These capabilities are crucial for accurately simulating wind turbine wakes and power capture,particularly in environments with variable atmospheric stability and complex topography.Field deployments and comparative assessments against traditional meteorological mast data demonstrate the effectiveness of LiSBOA.The method reduces wind velocity estimation errors to within 3%and increases the accuracy of turbulence intensity measurements by over 4%.Such improvements are significant for enhancing wind resource assessment,optimizing turbine placement,and refining control strategies for operational turbines.LiSBOA represents a robust advancement in LiDAR data processing for wind energy applications.By addressing limitations in spatial resolution and measurement uncertainty,it supports more reliable modeling of wake interactions and flow variability.This work contributes to improving the efficiency and reliability of wind energy systems through advanced remote sensing and statistical analysis techniques.
基金supported by the National Natural Science Foundation of China(Grants No.U21A2011,41971129)the National Key Research and Development Program of China(Grant No.2022YFF1300403)the Distinguished Membership Project of the Youth Innovation Promotion Association of CAS(Grant No.Y201812)。
文摘Agricultural terraces are significant for food provision,environmental stability and sustainable resource management.However,the spatiotemporal evolution of terraces and their influence on food productivity in mountainous landscapes remain poorly understood.Taking the Chinese Loess Plateau(LP)as an example,this study conducted multitemporal mapping of terraces and sloping croplands over three decades(1990-2020),systematically assessing their impacts on food output through terrain gradient analysis.The results indicated that:(1)the terraced area expanded in the past 30 years,particularly across steeper terrain gradients(third to fifth gradients);(2)sloping croplands predominantly occupied gentle slopes(first to second gradients),exhibiting area reduction correlating with urbanization processes;(3)the food provision increased extensively,with yield decreasing from southeast to northwest and regions of high yielding mainly in terraced fields;(4)over time,the variation of food provision correlated positively with the area of sloping cropland at low gradients,while at higher gradients,the expansion of terraces dominated the increase in food provision;(5)spatial clustering analysis revealed significant food productivity associated with high-density terrace distribution across steeper slope gradients.Low yields could be attributed to improper terrace management.This study clarified the impact of long-term terrace patterns on food provision and offered large-scale perspectives for terrace-based agriculture to enhance food security.Furthermore,the findings underscore the imperative of integrated land management in topographically complex regions,informing evidence-based policymaking for rational allocation and optimal utilization of terrace resources.
基金supported by Geological survey project of China Geological Survey(DD20230481,DD20242461)。
文摘Terrain and geological formation are crucial natural environmental factors that constrain land use and land cover changes.Studying their regulatory role in regional land use and land cover changes is significant for guiding regional land resource management.Taking the Danjiang River Basin in the Qinling Mountains of China as an example,this paper incorporates terrain(elevation,slope,and aspect)factors and geological formation to comprehensively analyse the differentiation characteristics of land use spatial patterns based on the examination of land use changes in 2000,2010,and 2020.Moreover,the geographical detector is employed to compare and analyse the effect of each factor on the spatial heterogeneity of land use.The results show that:(1)From 2000 to 2020,the areas of arable land and forestland in the Danjiang River Basin decreased while the areas of grassland,water areas,construction land,and unused land continuously increased.The comprehensive land use dynamics index was+0.09%,indicating a generally low level of land development.(2)Differences in the natural environmental factors of terrain and geological formation have a significant controlling effect on the spatial heterogeneity of land use.Specifically,there are notable differences in the advantageous distribution characteristics of various land use types across different levels of influencing factors.(3)The factor detection results reveal that geological formation has the strongest influence on the spatial heterogeneity of land use,followed by elevation and slope while aspect has the weakest influence.After the interaction among the factors,they nonlinearly enhance the explanation of spatial heterogeneity in land use.Overall,the influence of geological formation on the spatial heterogeneity of land use is greater than that of terrain factors.This study provides new geological evidence for natural resource management departments to conduct regional spatial planning,ecological and environmental protection and restoration,and land structure optimization and adjustment.
基金funded by the National Key Research and Development Program(Grants No.2023YFE0207900)。
文摘Accurate reconstruction of understory terrain is essential for environmental monitoring and resource management.This study integrates 1:10,000 Digital Elevation Model,Global Ecosystem Dynamics Investigation(GEDI),and AW3D30 Digital Surface Model data,combined with three machine learning algorithms—Random Forest(RF),Back Propagation Neural Network(BPNN),and Extreme Gradient Boosting(XGBoost)—to evaluate the performance of canopy height inversion and understory terrain reconstruction.The analysis emphasizes the impact of topographic and vegetation-related factors on model accuracy.Results reveal that slope is the most influential variable,contributing three to five times more to model performance than other features.In low-slope areas,understory terrain tends to be underestimated,whereas high-slope areas often result in overestimation.Moreover,the Normalized Difference Vegetation Index(NDVI)and land cover types,particularly forests and grasslands,significantly affect prediction accuracy,with model performance showing heightened sensitivity to vegetation characteristics in these regions.Among the models tested,XGBoost demonstrated superior performance,achieving a canopy height bias of-0.06 m,a root mean square error(RMSE)of 4.69 m for canopy height,and an RMSE of 9.82 m for understory terrain.Its ability to capture complex nonlinear relationships and handle high-dimensional data underlines its robustness.While the RF model exhibited strong stability and resistance to noise,its accuracy lagged slightly behind XGBoost.The BPNN model,by contrast,struggled in areas with complex terrain.This study offers valuable insights into feature selection and optimization in remote sensing applications,providing a reference framework for enhancing the accuracy and efficiency of environmental monitoring practices.
基金supported by the National Natural Science Foundation of China(Grants No.42322110 and 42271415)。
文摘Large-scale urban land expansion in mountainous and hilly areas(UEMH)has significantly altered the terrain in many Chinese cities,leading to various environmental and urban challenges.Despite its importance,there is limited nation-scale research that reveals the amount and the spatial variations of UEMH-induced terrain alteration.This research integrates the Global Annual Urban Dynamics dataset,the Global Basic Landform Unit dataset,the TanDEM-X DEM Change Map(DCM)dataset,Baidu Points-of-Interest(POI),and other auxiliary datasets to conduct a comprehensive analysis of terrain alteration induced by UEMH in China from 2012 to 2020.The results indicate that the country-wide UEMH-induced terrain alteration reached approximately 13 billion m^(3),which is about 100 times the volume of Hangzhou West Lake,and terrain alteration volume in over 300 counties exceeded 10 million m^(3).The Southwest and Southeast regions,which are ecologically sensitive and critical,feature the greatest alteration in terms of area and volume.The most significant terrain alteration in terms of intensity is observed in the Southwest and Hengduan Mountain Area.Additionally,there are significant spatial variations in the contributions of different urban functional zones to terrain alteration.Our findings indicate that urban land expansion in mountains and hills has significantly altered terrain in some regions of China,necessitating customized urban planning strategies for better managing mountainous urban land expansion and governance policies to address the geological,ecological,and urban development challenges.
文摘In order to slove a realistic test problem of TF/TA algorithm, it is necessary to make a discrete terrain model. The model has adjustable roughness parameters so as to test the optimization procedure for different types of terrain. In this paper, an algorithm to generate random terrain data is given.
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.
文摘[Objective]The aim was to study the distribution characteristics of terrain reflected radiation in Fujian Province.[Method]Based on solar radiation data,digital elevation model(DEM)and surface meteorological observation data in Fujian Province,plus surface albedo obtained by using remote sensing inversion method,the distribution of terrain reflected radiation in Fujian Province from 1988 to 2007 was simulated,and then its temporal and spatial distribution characteristics was studied.[Result]The simulation results of terrain reflected radiation in Fujian Province was credible.Terrain reflected radiation in Fujian Province was the highest in July(about 160 MJ/m2)and lowest in January(about 60 MJ/m2),and it was obviously higher from May to August compared with other months,while the order of terrain reflected radiation in four seasons was summer>spring>autumn>winter,and complex terrain affected the distribution of terrain reflected radiation greatly,especially in autumn and winter when sun elevation angle was small.In addition,terrain reflected radiation in most areas of Fujian Province was below 100 MJ/m2,and it was high in Ningde,Sanming and Nanping City in northern Fujian,while the maximum value(630 MJ/m2)could be found in Dong’an Island in Xiapu County in Ningde City and had good utilization value.[Conclusion]The study could provide theoretical foundation for the development and utilization of solar energy resources under complex terrain in China.
文摘A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics process, and by means of reducing the height of Yunnan-Guizhou Plateau and cutting off the middle-east of the Yunnan-Guizhou Plateau on the simulated tests, the question as how the ladder terrain on the west of Yunnan-Guizhou Plateau impact on the rainstorm of Guizhou was studied. The analysis results showed that the second ladder terrain of Yunnan-Guizhou Plateau only affected the development of convective clouds on its backward position,and hardly affected the rain on its upward. The whole terrain of the Yunnan-Guizhou Plateau had a distinct impact not only on the windward slope rainfall of the west of the plateau, but also on the rainfall distribution, intensity and continuing time of the convective clouds on the middle-east of the plateau.
基金Pre-Research Program of General Armament Department during the11th Five-Year Plan Period (No51309020503)the National Defense Basic Research Program of China (973Program)(No973-61334)+1 种基金the National Natural Science Foundation of China(No50575042)Specialized Research Fund for the Doctoral Program of Higher Education (No20050286026)
文摘To improve the navigation accuracy of an autonomous underwater vehicle （AUV）, a novel terrain passive integrated navigation system （TPINS） is presented. According to the characteristics of the underwater environment and AUV navigation requirements of low cost and high accuracy, a novel TPINS is designed with a configuration of the strapdown inertial navigation system （SINS）, the terrain reference navigation system （TRNS）, the Doppler velocity sonar （DVS）, the magnetic compass and the navigation computer utilizing the unscented Kalman filter （UKF） to fuse the navigation information from various navigation sensors. Linear filter equations for the extended Kalman filter （EKF）, nonlinear filter equations for the UKF and measurement equations of navigation sensors are addressed. It is indicated from the comparable simulation experiments of the EKF and the UKF that AUV navigation precision is improved substantially with the proposed sensors and the UKF when compared to the EKF. The TPINS designed with the proposed sensors and the UKF is effective in reducing AUV navigation position errors and improving the stability and precision of the AUV underwater integrated navigation.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51179035 and 51279221)the Natural Science Foundation of Heilongjiang Province(Grant No.E201121)
文摘To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrainmatching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation（LSE） is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.
基金National Natural Science Foundation of China,No.41930102,No.41971333,No.41771415。
文摘Digital terrain analysis(DTA)is one of the most important contents in the research of geographical information science(GIS).However,on the basis of the digital elevation model(DEM),many problems exist in the current research of DTA in geomorphological studies.For instance,the current DTA research appears to be focused more on morphology,phenomenon,and modern surface rather than mechanism,process,and underlying terrain.The current DTA research needs to be urgently transformed from the study of landform morphology to one focusing on landform process and mechanism.On this basis,this study summarizes the current research status of geomorphology-oriented DTA and systematically reviews and analyzes the research about the knowledge of geomorphological ontology,terrain modeling,terrain derivative calculation,and terrain analytical methods.With the help of DEM data,DTA research has the advantage of carrying out geomorphological studies from the perspective of surface morphology.However,the study of DTA has inherent defects in terms of data expression and analytic patterns.Thus,breakthroughs in basic theories and key technologies are necessary.Moreover,scholars need to realize that DTA research must be transformed from phenomenon to mechanism,from morphology to process,and from terrain to landform.At present,the research development of earth science has reached the critical stage in which the DTA research should focus more on geomorphological ontology.Consequently,this study proposes several prospects of geomorphology-oriented DTA from the aspects of value-added DEM data model,terrain derivatives and their spatial relations,and macro-terrain analysis.The study of DTA based on DEM is at a critical period along with the issue on whether the current GIS technology can truly support the development of geography.The research idea of geomorphology-oriented DTA is expected to be an important exploration and practice in the field of GIS.
基金Supported by Innovation Program of Shanghai Municipal Education Commission (No.10ZZ25)the Key Laboratory of Geo-informatics of State Bureau of Surveying and Mapping (No.200914)
文摘Based on the estimating rule of the normal vector angles between two adjacent terrain units, we use the concept of terrain complexity factor to quantify the terrain complexity of DEM, and then the formula of terrain complexity factor in Raster DEM and TIN DEM is deduced theoretically. In order to make clear how the terrain complexity factor ECF and the average elevation h affect the accuracy of DEM terrain representation RMSEEt, the formula of Gauss synthetical surface is applied to simulate several real terrain surfaces, each of which has different terrain complexity. Through the statistical analysis of linear regression in simula- tion data, the linear equation between accuracy of DEM terrain representation RMSEEt, terrain complexity factor ECF and the average elevation h is achieved. A new method is provided to estimate the accuracy of DEM terrain representation RMSEEt with a certain terrain complexity and it gives convincing theoretical evidence for DEM production and the corresponding error research in the future.
