DEM分辨率对黄土侵蚀沟形态特征表达的不确定性分析

黄土侵蚀沟的地形表达是开展黄土沟谷侵蚀研究的基础工作,利用数字高程模型(DEM)定量描述侵蚀沟特征有助于研究侵蚀沟的形态变化和发育过程。基于DEM数据计算多种指标对黄土侵蚀沟特征进行描述是目前侵蚀沟研究中最为常用的方法。但是,受到格网DEM数据结构的限制,其计算结果会存在一定的不确定性。在侵蚀沟地形表达时,对形态特征的表达会受到DEM数据分辨率的影响,进而造成表达结果的不确定性。尤其在黄土高原地区,地形特征更为破碎,地形要素更为复杂,其表达结果受DEM分辨率的影响更为明显。本文以黄土高原典型样区为例,基于点云数据建立不同分辨率的DEM数据集,通过不同地形因子对侵蚀沟特征进行表达,分析DEM分辨率在黄土侵蚀沟形态特征表达时的不确定性。结果显示,分辨率的降低对主沟支沟比和纵比降等侵蚀沟形态特征因子产生了较大影响,且指标与分辨率多呈现线性变化关系。但是,随着侵蚀沟的横向扩张,DEM分辨率对其特征表达的影响逐渐被削弱。此外,在使用固定分析窗口进行侵蚀沟特征计算时,由于分辨率的降低,格网尺寸增大,其实际分析半径随之增大,使得计算范围内地表形态变化增加,导致沟谷切割深度随着分辨率的降低反而增加。同时,侵蚀沟主沟道区域受分辨率影响较小,沟头区域指标与分辨率的关系较弱。     

地形扫描数据TIN模型生成DEM的误差计算方法

由地表三维空间数据生产的数字高程模型(DEM)的误差包括从数据误差传递来的误差和因数据数量不足以反映地形起伏造成的信息损失误差。本文给出了由三维空间数据的不规则三角网(TIN)模型栅格化为DEM过程中,通过线性插值将数据随机误差传递到DEM栅格上的随机误差的解析解,同时利用地基激光扫描仪测量的冲沟地形数据点云,分析得出因信息损失产生的DEM系统和随机误差的估算方法。结果显示信息损失产生的DEM平均高程系统误差和随机误差都与有效测点密度有关,其中有效测点由TIN中包含DEM栅格中心点的所有三角面的3个顶点组成;信息损失产生的DEM平均高程系统误差和随机误差除与有效测点密度相关外,还与地形特征有关,平均高程系统误差与地形整体凹度参数有关,随机误差与地形整体起伏程度参数有关。建立了分辨率为0.1 m×0.1 m的DEM误差估算模型。     

顾及地表汇水分析的城市DEM构建

城市暴雨内涝是城市最普遍的自然灾害之一。受城市复杂下垫面环境的影响,城市暴雨积水具有响应时间短、淹没速度快的特点。数字高程模型（Digital Elevation Model, DEM）是城市地表汇水分析的关键,是暴雨积水分析的基础,而传统方法构建的DEM不能满足复杂下垫面环境下城市暴雨积水淹没分析的需求。本文以构建顾及地表汇水分析的城市DEM为目的,提出基于多源数据融合思想和地形修正思想的DEM构建方法,即将数字摄影测量技术构建的大范围DEM与车载激光扫描技术构建的城市道路高精度DEM相融合,再利用影响雨水汇流路径的建筑物、水系等要素对DEM进行修正的构建方法。本文以北京市海淀区公主坟地区为例进行研究,结果表明该方法构建的DEM在道路区域高程精度可达厘米级,实现了对城市道路易积水区域的重点表达,基于该DEM的汇水分析结果基本符合城市下垫面汇水特点,因此,本文构建的DEM适用于城市道路、桥区汇水路径分析和积水淹没分析。     

数字河网提取的影响参数优化分析

数字高程模型(Digital Elevation Model,DEM)是提取数字河网的主要数据源.但是,由于在受到带有尺度效应的DEM空间分辨率和数字河网提取过程中,汇流面积阈值等参数的影响,使得河网提取的结果具有很大的主观性,因此,如何优化两者的取值,对于更准确地模拟地表河网具有重要的意义.本文以厦门市作为研究区,以...     

基于街道空间数据及GPS测量的SRTM-DEM校正和插值细化

针对城市地区SRTM数字高程模型,本文引入街道空间分布信息作为辅助数据,并结合GPS实地测量,对DEM中具有空间相关性的误差部分进行修正,从而尝试在一定程度上提高SRTM数据的垂直精度和空间分辨率.本文以墨西哥城Xico地区为例,解析SRTM DEM像元分辨率单元内地物表面平均高程值的组成结构;分析形成DEM高程值的地...     

CryoSat DEM与多种南极DEM的对比分析

南极洲被巨厚冰雪覆盖,地质构造以南极横断山脉为界,总体分为东南极地盾和西南极活动带。数字高程模型（DEM）是研究南极冰盖变化的基础数据之一。通过多期次数字高程模型相比较获得高程的变化信息,是分析南极冰盖厚度变化和物质平衡的重要手段。然而不同类型DEM之间存的平面误差和垂直误差影响分析结果的精度。首先利用配准消除DEM间的水平误差,然后计算并按坡度提取CryoSat DEM与其他DEM的平均高程差和标准差,最后分析高程差的时空变化特征。通过分析发现,DEM之间存在不同的平面误差。其中TanDEM_X DEM与CryoSat DEM的高程平面偏差最小,而ICESat DEM与CryoSat DEM的高程平面偏差最大。在垂直方向上,0°~1°的坡度范围内,CryoSat DEM与TanDEM_X DEM的平均高程差在3.5~5.5 m之间,标准差小于18.0 m;CryoSat DEM和Bamber 1km DEM的平均高程差在-2.5~+1.0 m之间,标准差小于24.2 m;CryoSat DEM与ICESat DEM的平均高程差在-25.0~-1.0 m之间,标准差小于47.2 m;CryoSat DEM与RAMPv2 DEM的平均高程差在1.3~3.2 m之间,标准差小于45.6 m。通过研究发现南极冰盖内部高程增加,但西南极冰盖和东南极冰盖高程均在降低,且西南极降低明显,同时南极边缘地区高程降低明显。本研究为全球变化研究和南极物质平衡研究提供了重要参考。      

浅谈数字高程模型质量检验方法

随着GIS、数字地球的发展,数字高程模型DEM成为空间信息系统的重要组成部分,是各个应用领域重要的基础数据。本文以国家西部1:50000地形图测绘项目为例,阐述数字高程模型(DEM)质量的检验方法。     

基于地貌特征的数字高程模型融合方法

数字高程模型（Digital Elevation Model, DEM）是一种至关重要的空间信息,广泛应用于各行各业。其中,ASTER GDEM与SRTM几乎覆盖了全球陆域,为地学研究提供了非常实用的高程数据支撑,但是由于二者传感器采集数据原理的不同,使得高程数据在不同地貌条件下的高程精度亦存在程度不一的误差。本文提出了一种新型的基于地貌特征的DEM融合方法,使得融合GDEM与SRTM后的DEM数据,消除了地貌特征的影响、显著地提高了DEM质量。该方法主要分为地理配准和高程融合2个步骤：①基于河流线对等线性地貌特征的位置数据,构建了GDEM与SRTM的水平偏移相关的误差评价函数,采用多级网格搜索法求得DEM间的水平偏移距离,实现对DEM的配准;②按照DEM高程值在不同地貌单元及边界线附近的高程变化特征,建立地貌分区的高程融合模型来融合两种地理配准后的DEM高程,尤其是实现了地貌单元边界线附近的高程平滑过渡。本文以怀柔北部地区为实验区,以1:5万地形图为参考,对2种DEM数据进行融合,统计结果表明：① 融合DEM在各地貌单元的误差均显著下降,地形表达较之融合前更加精确;② 高程差呈现正态分布,明显区别于融合前DEM不对称的多峰分布形态,说明地貌影响被有效地剔除;③ GDEM和SRTM数据的精度对坡度有较大依赖性,融合后DEM的精度在不同坡度范围下均优于GDEM和SRTM,显著降低了融合前DEM对坡度的依赖程度;④ 在不同坡向下,GDEM和SRTM的RMSE取值波动较大,融合DEM的RMSE取值在各方向表现稳定,高程精度较GDEM和SRTM有显著提高。     

机载LiDAR点云密度和插值方法对DEM及地表粗糙度精度影响分析

机载LiDAR点云是获取高质量数字高程模型(Digital Elevation Model, DEM)的主要数据源,而地表粗糙度作为DEM的主要派生产品,在地学研究中发挥了重要作用,但点云密度和插值方法对DEM及地表粗糙度精度影响程度并没有明确结论。为此,本文利用不同地形条件下的林区机载LiDAR点云为实验对象,将原始点云随机缩减为不同的采样密度,利用5种常用插值方法(克里金(Ordinary Kriging, OK),径向基函数(Radial Basis Function, RBF),不规则三角网(Triangulated Irregular Network, TIN),自然邻域(Natural Neighbor, NN)和反距离加权(Inverse Distance Weighting, IDW))构建各个测区不同采样密度条件下的DEM,并通过空间特征和统计特征两方面对DEM及其地表粗糙度精度分析。结果表明:(1) DEM插值算法的精度随点云密度缩减而降低,且数据量缩减至原始数据量的30%后,不同算法精度区别较为明显,其中,RBF和OK精度最优,IDW精度最低;(2) DEM误差与...     

基于数字高程模型的公路勘察设计

根据公路勘测设计的特点,阐述了数字高程模型(DEM)的概念和特点以及数字高程模型的建模方式,讨论了适应于公路勘查设计的数字高程模型数据采集方法等问题,总结了数字高程模型在公路勘察设计中的应用。     

多模型协同下的城郊地区DEM构建方法研究

人类活动对地表的改造使其呈现形态多样化、不连续等特征,此时传统的DEM构建方法难以满足这些区域DEM精度要求。为此,本文提出了一种多模型协同构建DEM的思路,首先按照形态特征和语义信息对地形进行分类,然后对不同类型的地形区域,选择、设计适宜的方法分别进行DEM构建,最后将不同区域构建DEM结果融合拼接形成区域完整的DEM结果。本文选择江苏省南京市城市郊区某区域为实验区,以1:500比例尺地形图为基本数据源进行DEM构建实验。实验结果表明,与传统经典DEM构建方法相比,本文提出的多模型协同的DEM构建方法能够有效表达实验区域不同的地形特征,特别是对于人工改造的地形(如道路、边坡等区域),本文方法构建的DEM其形态精度优势显著;同时,基于验证点法的高程精度分析结果表明,本文方法构建DEM的高程精度亦优于传统DEM构建方法,特别是对于一些形态规则而高程信息相对稀少的区域,以边坡区域为例,经典DEM构建法平均误差均超过5 m,而本文构建结果平均误差为0.26 m,精度优势非常明显。研究表明本文提出的多模型协同的DEM构建方法适用于人类活动改造或显著影响的区域的DEM构建。     

浅谈寻找隐伏矿床的理论和方法

本文从地质勘查找矿角度,将未出露现代侵蚀面或被沉积物覆盖的矿床统称为隐伏矿床。寻找隐伏矿的理论和方法可分为：①地质分析（构造体系、地质建造、矿田构造、隐伏侵入体等）;②矿床学理论（成因模式、找矿模型等）;③数学地质（统计预测、综合信息、地质异常等）;④地球化学找矿（构造地球化学、原生矿晕、次生矿晕、离子态分布模式）;⑤地球物理找矿（层析成像、地电提取、物探填图等）;⑥矿物学方法（矿物标型、蚀变矿物等）;⑦遥感地质找矿;⑧其他方法（生物找矿、计算机技术等）。     

顾及DEM误差空间自相关的地形变化检测方法

传统的地形变化检测方法忽略了DEM误差的空间自相关性,针对此问题,本文提出了顾及DEM误差空间自相关的地形变化检测方法。首先,通过2期DEM相减得到差值DEM（DoD）,并通过蒙特卡罗方法评估DEM的误差空间分布;其次,基于DEM误差空间分布图,通过误差传播公式计算DoD误差,并使用半变异函数分析其空间自相关程度;最后,在误差空间自相关分析和显著性检测的基础上计算地形变化量（体积）和对应的误差限。本文在4个黄土小流域进行了实验,结果表明：无人机摄影测量DEM的高程误差存在一定程度的空间自相关,通过光束平差蒙特卡罗方法可以模拟无人机摄影测量DEM的误差空间分布;在进行地形变化检测时,使用误差空间分布代替中误差进行地形变化检测有效降低了检测结果对显著性阈值的敏感性;显著性阈值从68%提高到95%时,使用误差空间分布的检测结果损失的观测值比使用中误差低5.39%~6.75%。顾及空间自相关的地形变化检测方法能够更加科学、精确地量化地形变化特征,也可有效地应用于地表变形监测、流域侵蚀监测、输沙量评估等领域。     

改造末期多种能源矿藏(床)同盆共存的多源信息找矿识别标志

利用多源信息(地质、物化探、遥感、水文地质等)研究多种能源矿种在改造末期同盆共存的判识标志和赋存环境，着眼于改造结果，多源信息特征反映的是在改造末期所形成构造格局的基础上，油气、煤、铀多种能源矿藏(床)同盆共存的现今空间关系，在此基础上，从铀成矿因素方面建立油气、煤、铀多种能源矿藏(床)同盆共存的找矿识别标志。     

Managing Soil Erosion Potential by Integrating Digital Elevation Models with the Southern China＇s Revised Universal Soil Loss Equation——A Case Study for the West Lake Scenic Spots Area of Hangzhou, China

In China, many scenic and tourism areas are suffering from the urbanization that results from physical development of tourism projects, leading to the removal of the vegetative cover, the creation of areas impermeable to water, in-stream modifications, and other problems. In this paper, the risk of soil erosion and its ecological risks in the West Lake Scenic Spots （WLSS） area were quantitatively evaluated by integrating the revised universal soil loss equation （RUSLE） with a digital elevation model （DEM） and geographical information system （GIS） software. The standard RUSLE factors were modified to account for local climatic and topographic characteristics reflected in the DEM maps, and for the soil types and vegetation cover types. An interface was created between the Areinfo software and RUSLE so that the level of soil erosion and its ecological risk in the WLSS area could be mapped immediately once the model factors were defined for the area. The results from an analysis using the Areinfo-RUSLE interface showed that the risk value in 93 % of the expanding western part of the WLSS area was moderate or more severe and the soil erosion risk in this area was thus large compared with that in the rest of the area. This paper mainly aimed to increase the awareness of the soil erosion risk in urbanizing areas and suggest that the local governments should consider the probable ecological risk resulting from soil erosion when enlarging and developing tourism areas.     

Managing Soil Erosion Potential by Integrating Digital Elevation Models with the Southern China's Revised Universal Soil Loss Equation——A Case Study for the West Lake Scenic Spots Area of Hangzhou,China

In China,many scenic and tourism areas are suffering from the urbanization that results from physical development of tourism projects,leading to the removal of the vegetative cover,the creation of areas impermeable to water,in-stream modifications,and other problems. In this paper,the risk of soil erosion and its ecological risks in the West Lake Scenic Spots (WLSS) area were quantitatively evaluated by integrating the revised universal soil loss equation (RUSLE) with a digital elevation model (DEM) and geographical information system (GIS) software. The standard RUSLE factors were modified to account for local climatic and topographic characteristics reflected in the DEM maps,and for the soil types and vegetation cover types. An interface was created between the Arcinfo software and RUSLE so that the level of soil erosion and its ecological risk in the WLSS area could be mapped immediately once the model factors were defined for the area. The results from an analysis using the Arcinfo-RUSLE interface showed that the risk value in 93 % of the expanding western part of the WLSS area was moderate or more severe and the soil erosion risk in this area was thus large compared with that in the rest of the area. This paper mainly aimed to increase the awareness of the soil erosion risk in urbanizing areas and suggest that the local governments should consider the probable ecological risk resulting from soil erosion when enlarging and developing tourism areas.     

额尔古纳—满洲里地区中生代火山岩与铀成矿地质条件研究

与我国相毗邻的蒙古、俄罗斯超大型火山岩型铀矿床的发现促进了我国对额尔古纳—满洲里地区中生代火山岩铀成矿条件的研究。在野外调研、样品分析及资料综合整理基础上，本文从火山岩的火山喷发旋回与演化、岩性组合、岩石铀含量、岩石化学及火山岩形成环境方面分析了该区中生代火山岩的铀成矿地质条件，认为该区与国内外产铀火山岩特征相似，成矿地质条件优越，是我国超大型火山岩型铀矿床极具远景的地区。     

A new treatment of depression for drainage network extraction based on DEM

Depressions in landscapes function as buffers for water and sediment. A landscape with depressions has less runoff, less erosion and more sedimentation than that without depressions. Sinks in digital elevation models （DEMs） can be considered the real features that represent depressions in actual landscapes or spurious features that result from errors in DEM creation. In many hydrological and erosion models, all sinks are considered as spurious features and, as a result, these models do not deal with the sinks that represent real depressions. Consequently, the surface runoff and erosion are overestimated due to removing the depressions. Aiming at this problem, this paper presents a new method, which deal with the sinks that represent real depressions. The drainage network is extracted without changing the original DEM. The method includes four steps： detecting pits, detecting depressions, merging depressions, and extracting drainage network. Because the elevations of grid cells are not changed, the method can also avoid producing new fiat areas, which are always produced by the conventional filling methods. The proposed method was applied to the Xihanshui River basin, the upper reach of the Jialingjiang River basin, China, to automatically extract the drainage network based on DEM. The extracted drainage network agrees well with the reality and can be used for further hydrologic analysis and erosion estimation.     

Comparison of DEM accuracies generated from different stereo pairs over a plateau mountainous area

Digital elevation models(DEMs) can be quickly and conveniently generated using very high resolution(VHR) satellite stereo images. Previous studies have evaluated and compared DEM accuracy based on VHR satellite stereo pairs collected by different satellite sensors. However, few studies analyzed the accuracy of a DEM based on stereo image pairs from a satellite with the same orbit and different orbits for a region with significant topographic fluctuations in the plateau area. Referring to former studies, this paper had two objectives: to generate a digital elevation model(DEM) and evaluate its horizontal and vertical accuracy over a plateau area with high relief; and to study the mapping capability of multiorbit and multitemporal stereo pair images in the plateau mountainous region. To achieve these objectives, we collected the 2015 Worldview-2 stereo image pair and another three World View-2 images acquired in 2013, 2014, and 2015. First, the 2015 DEM was obtained using a strict physical model based on along-track stereo image pairs, and the reliability of the DEM was verified with field data. Then, the images obtained in 2013, 2014, and 2015 were combined into different-orbit stereo image pairs, DEMs were produced using rational function models, and the DEMs were verified using field data and the 2015 DEM as standards. The results showed that the relief degree has a particular influence on the DEM, and the precision of the DEM decreases as the topographic relief increases. Off-nadir angles can also influence DEM accuracy, with a larger angle corresponding to a lower DEM accuracy. The research also shows that the DEM obtained from four sets of experiments meets the accuracy requirement of a 1:5,000 digital elevation map, digital line graphic(DLG), and digital orthophoto map(DOM). Among these four groups of DEMs, the one based on the 2015 stereo pairs with the same satellite achieved the highest precision.