Image classification-based ground filtering of point clouds extracted from UAV-based aerial photos     

Volkan Yilmaz  Berkant Konakoglu  Cigdem Serifoglu  Oguz Gungor  Ertan Gökalp 《国际地球制图》2018,33(3):310-320

With the advent of unmanned aerial vehicles (UAVs) for mapping applications, it is possible to generate 3D dense point clouds using stereo images. This technology, however, has some disadvantages when compared to Light Detection and Ranging (LiDAR) system. Unlike LiDAR, digital cameras mounted on UAVs are incapable of viewing beneath the canopy, which leads to sparse points on the bare earth surface. In such cases, it is more challenging to remove points belonging to above-ground objects using ground filtering algorithms generated especially for LiDAR data. To tackle this problem, a methodology employing supervised image classification for filtering 3D point clouds is proposed in this study. A classified image is overlapped with the point cloud to determine the ground points to be used for digital elevation model (DEM) generation. Quantitative evaluation results showed that filtering the point cloud with this methodology has a good potential for high-resolution DEM generation.  相似文献   

疏勒河上游河流地貌特征及其演化     

褚永彬  朱利东  陈伟  张建国  杨文光  陶刚 《第四纪研究》2015,35(2)

疏勒河上游位于中祁连地块,受到中祁连南缘断裂带、中祁连北缘断裂带的差异控制,其地貌是青藏高原隆升的结果.本文以疏勒河上游为研究对象,应用ArcGIS水文分析工具,提取河流纵剖面、Hack剖面、SL参数以及HI,分析了河流的形态特征;提取流域边界高程剖面,分析了流域演化遗留的地貌证据.研究结果表明,疏勒河上游河流纵剖面以线性函数为最佳拟合函数,说明疏勒河上游河段整体上处于河流发育早期阶段;Hack剖面呈明显的凸形,说明第四纪以来流域所在地区处于强烈的构造抬升;河流流向转折、SL异常值以及河流纵剖面裂点具有良好的一致性,从流域边界剖面识别的垭口又与上述三者具有对应关系.综合上述河流特征及流域边界剖面所反映的信息,推测研究区发生过3次袭夺事件.古疏勒河、古昌马河以及古野马河的重组塑造了现在的疏勒河流域.  相似文献   

Drainage skeletonization from flow-accumulated area without the use of threshold     

Rajesh Kumar Sah 《国际地球制图》2015,30(8):894-904

This study presents a method of automatic drainage skeletonization from flow-accumulated area without the use of threshold which conserves drainage geometry at chosen digital elevation model (DEM) scale. To get all possible drainage at the chosen scale, stream order raster is generated by incorporating flow accumulation and flow direction raster derived from corresponding DEM. This allows generation of drainage network without the use of threshold. Resultant stream order raster, termed as raw stream order raster (RSOR), is tested against threshold defined stream order raster to evaluate its efficiency. Use of RSOR allows extraction of stream heads to greater stream head extent. Again, DEM downscaling takes care of overestimation in number of streams. So, the proposed technique is effective in controlling two basic aspects of drainage characteristics – stream number and extent. In our case, drainage estimated from re-sampled medium-scale DEM has the closest matching with that of the reference topographical map.  相似文献   

Topographic correction of ALOS-PALSAR images using InSAR-derived DEM     

Anup Das  Ritesh Agrawal  Shiv Mohan 《国际地球制图》2015,30(2):145-153

Topographic corrections of synthetic aperture radar (SAR) images over hilly regions are vital for retrieval of correct backscatter values associated with natural targets. The coarse resolution external digital elevation models (DEM) available for topographic corrections of high resolution SAR images often result into degradation of spatial resolution or improper estimation of backscatter values in SAR images. Also, many a times the external DEMs do not spatially co-register well with the SAR data. The present study showcases the methodology and results of topographic correction of ALOS-PALSAR image using high resolution DEM generated from the same data. High resolution DEMs of Jaipur region, India were generated using multiple pair SAR images acquired from ALOS-PALSAR using interferometric (InSAR) techniques. The DEMs were validated using differential global positioning system measured elevation values as ground control points and were compared with photogrammetric DEM (advanced spaceborne thermal emission and reflection radiometer – ASTER) and SRTM (Shuttle Radar Topography Mission) DEM. It was observed that ALOS-PALSAR images with optimum baseline parameters produced high resolution DEM with better height accuracy. Finally, the validated DEM was used for topographic correction of ALOS-PALSAR images of the same region and were found to produce better result as compared with ASTER and SRTM-DEM.  相似文献   

数字高程模型(DEM)成果裁切探讨     

徐丽丽  杨春全 《测绘与空间地理信息》2015,(6)

随着计算机技术及测绘产品的不断发展,数字高程模型(DEM)已成为地理信息空间系统和"数字地球"的重要组成部分。在测绘技术蓬勃发展的今天,数字高程模型(DEM)的生产已成为各生产部门较关注的问题之一,特别是近年来数字龙江地理空间框架建设一期工程对数字高程模型(DEM)产品成果的要求有很大提高,数字高程模型(DEM)成果的裁切也显得尤为重要,本文从工作中遇到的DEM成果裁切问题入手,结合笔者多年的测绘生产经验,研讨DEM成果裁切问题。  相似文献   

基于DWT的DEM重点区域多分辨率伪装技术     

陈令羽  宋国民  王乃科  徐齐 《测绘科学技术学报》2015,32(2):202-206

在数据共享中,保护重要高程数据的信息安全十分重要,提出了一种针对DEM重点区域进行多分辨率伪装和分权限还原的信息保护方法。结合传统信息保护技术的特点,分析DEM数据重点区域多分辨率伪装的流程和特点,介绍了重点区域数据置乱以及原始数据高程漏洞填充等进行信息伪装的数据准备和预处理方法。结合DWT算法能够进行多分辨率分解的特点,实现了DEM重点区域的多分辨率信息伪装与还原。通过实验分析,证明了该方法的可行性,可以为不同权限的用户提供适当精度的高程数据,能够保证DEM数据特别是重点区域在存储和传输中的信息安全。  相似文献   

低空无人机双介质水下礁盘深度测量试验与分析   总被引：1，自引：0，他引：1  

周高伟  李英成  任延旭  盛琳  叶冬梅  范凤云  白洁 《测绘学报》2015,44(5):548-554

以双介质摄影测量原理为基础,利用海岛无人机影像开展了航空双介质摄影测量试验与分析。首先简单介绍了双介质摄影测量原理,论述了双介质摄影测量对海水折射率的精度要求,提出了一种解算高程改正系数方法,在此基础上开展了基于某岛低空无人机影像的双介质水下礁盘深度量测试验。试验表明,航空双介质摄影测量在实际应用中是可行的,对航空摄影条件要求比较高。  相似文献   

Modelling of piping collapses and gully headcut landforms:Evaluating topographic variables from different types of DEM   总被引：1，自引：0，他引：1  

Alireza Arabameri  Fatemeh Rezaie  Subodh Chandra Pal  Artemi Cerda  Asish Saha  Rabin Chakrabortty  Saro Lee 《地学前缘(英文版)》2021,12(6):129-146

The geomorphic studies are extremely dependent on the quality and spatial resolution of digital elevation model(DEM)data.The unique terrain characteristics of a particular landscape are derived from DEM,which are responsible for initiation and development of ephemeral gullies.As the topographic features of an area significantly influences on the erosive power of the water flow,it is an important task the extraction of terrain features from DEM to properly research gully erosion.Alongside,topography is highly correlated with other geo-environmental factors i.e.geology,climate,soil types,vegetation density and floristic composition,runoff generation,which ultimately influences on gully occurrences.Therefore,terrain morphometric attributes derived from DEM data are used in spatial prediction of gully erosion susceptibility(GES)mapping.In this study,remote sensing-Geographic information system(GIS)tech-niques coupled with machine learning(ML)methods has been used for GES mapping in the parts of Semnan province,Iran.Current research focuses on the comparison of predicted GES result by using three types of DEM i.e.Advanced Land Observation satellite(ALOS),ALOS World 3D-30 m(AW3D30)and Advanced Space borne Thermal Emission and Reflection Radiometer(ASTER)in different resolutions.For further progress of our research work,here we have used thirteen suitable geo-environmental gully erosion conditioning factors(GECFs)based on the multi-collinearity analysis.ML methods of conditional inference forests(Cforest),Cubist model and Elastic net model have been chosen for modelling GES accordingly.Variable's importance of GECFs was measured through sensitivity analysis and result show that elevation is the most important factor for occurrences of gullies in the three aforementioned ML methods(Cforest=21.4,Cubist=19.65 and Elastic net=17.08),followed by lithology and slope.Validation of the model's result was performed through area under curve(AUC)and other statistical indices.The validation result of AUC has shown that Cforest is the most appropriate model for predicting the GES assessment in three different DEMs(AUC value of Cforest in ALOS DEM is 0.994,AW3D30 DEM is 0.989 and ASTER DEM is 0.982)used in this study,followed by elastic net and cubist model.The output result of GES maps will be used by decision-makers for sustainable development of degraded land in this study area.  相似文献   

Impact of Water Vapor on Elevation-dependent Climate Change     

ZHANG Xianzhou  WANG Ling  HE Yongtao  DU Mingyuan  ZHANG Jing  SHI Peili  YU Chengqun  ZHANG Yangjian 《资源与生态学报(英文版)》2017,8(1):5-9

Elevation dependency amongst climate change signals has been found in major mountain ranges around the world, but the main factors causing this dependency have not been clarified. In this study, four different datasets of observation and reanalysis for China were used to examine the elevation dependency of climate change. A lack of consistency was found in dependency between warming magnitude and elevation across the Tibetan Plateau and China. However, a dependency of climate change on water vapor was detected whereby the temperature trend initially increased at low specific humidity, and then decreased as specific humidity increased. At ground level the maximum trend in temperature appeared in the specific humidity range 2.0-3.0 g kg^-1. This suggests that water vapor is a mediator of climate change and may be responsible for elevation-dependent climate change.  相似文献   

大地水准面起伏对重力归算的影响研究     

张品  申重阳  杨光亮  王同庆  陈兆辉  张双喜 《大地测量与地球动力学》2017,37(3):306-310

针对目前重力探测中重力改正时常用的两个高程参考系统存在偏差这一事实,选取两个大地水准面起伏变化较大的剖面区域,分析大地水准面起伏对重力归算的影响。结果表明,剖面跨度和剖面大地水准面起伏梯度都会对布格重力异常产生影响,所以当重力探测区域大地水准面起伏差距较大时,大地水准面与参考椭球面之间的差异对重力归算的影响比较突出,在利用布格重力异常反演、解释地壳密度结构时,大地水准面起伏的影响必须考虑。  相似文献