Chinese progress in geomorphometry

Geomorphometry, the science of digital terrain analysis (DTA), is an important focus of research in both geomorphology and geographical information science (GIS). Given that 70% of China is mountainous, geomorphological research is popular among Chinese scholars, and the development of GIS over the last 30 years has led to significant advances in geomorphometric research. In this paper, we review Chinese progress in geomorphometry based on the published literature. There are three major areas of progress: digital terrain modelling methods, DTA methods, and applications of digital terrain models (DTMs). First, traditional vector- and raster-based terrain modelling methods, including the assessment of uncertainty, have received widespread attention. New terrain modelling methods such as unified raster and vector, high-fidelity, and real-time dynamic geographical scene modelling have also attracted research attention and are now a major focus of digital terrain modelling research. Second, in addition to the popular DTA methods based on topographical derivatives, geomorphological features, and hydrological factors extracted from DTMs, DTA methods have been extended to include analyses of the structure of underlying strata, ocean surface features and even socioeconomic spatial structures. Third, DTMs have been applied to fields including global climate change, analysis of various typical regions, lunar surface and other related fields. Clearly, Chinese scholars have made significant progress in geomorphometry. Chinese scholars have had the greatest international impact in areas including high-fidelity digital terrain modelling and DTM-based regional geomorphological analysis, particularly in the Loess Plateau and the Tibetan Plateau regions.     

海相火山岩区地质填图方法——以北祁连山东段白银矿田古火山机构厘定为例

20世纪90年代以来,火山机构控矿理论在海相火山岩区块状硫化物矿床研究中得到了越来越多的关注,基于该理论的指导,在北祁连山东段的白银矿田取得了找矿突破性进展。其间,详细的海相火山岩相地质填图工作为白银矿田火山机构与成矿联系的研究及找矿突破奠定了坚实的基础。反映出在海相火山岩区推行合理可行的火山岩相地质填图方法至关重要。以白银矿田海相火山岩区为例,首先,对该区大比例尺火山岩相填图及古火山机构厘定成果进行介绍;其次,通过分析、借鉴此成功案例,总结海相火山岩区填图内容和技术方法;最后,阐述应用该方法在北祁连山中段祁连县一带海相火山岩区进行大比例尺填图的成功尝试。     

基于EGM2008和剩余地形模型的区域似大地水准面精化方法

利用EGM2008计算重力场模型高程异常,结合SRTM和DTM2006.0计算剩余地形模型,进而计算RTM高程异常,以弥补EGM2008重力场模型短波信号缺失的不足。从实测高程异常中减去重力场模型高程异常以及RTM高程异常,得到残余高程异常。利用曲面拟合方法拟合残余高程异常模型,解决高程基准系统偏差问题。通过实际GPS/水准数据计算证明,该方法能显著提高GPS点的高程异常计算精度,达到精化区域似大地水准面的目的。     

遥感技术在复杂山区页岩气早期勘探中的应用

我国目前公开招标的页岩气区块多数位于四川盆地东南缘高陡构造带,地形复杂,断裂发育,造成区块内页岩气的勘探和开发均存在一定难度.与盆地内覆盖区的页岩气早期勘探不同,复杂山地内的页岩气早期勘探需考虑地表地貌因素,加强早期研究,降低勘探风险和成本.利用湖南保靖地区的页岩气招标区块的遥感数据,与DEM数据相结合,考虑坡度、高程2个因素,优选研究区页岩气勘探的地貌有利区,为下一步页岩气的勘探和后期施工提供参考.     

栅格数字地形分析中的尺度问题研究方法

栅格数字高程模型（DEM）固有的尺度特征给以栅格DEM为基本输入的数字地形分析带来各种尺度问题。对栅格数字地形分析中涉及的尺度进行梳理,以分辨率和分析窗口为重点,对栅格数字地形分析中的多尺度表达、尺度效应、适宜尺度选择、尺度转换等尺度问题及其相互关系进行阐述;分别介绍各类尺度问题的现有定量研究方法,尤其对尺度效应定量刻画和适宜尺度选择方法,根据不同方法计算定量指标所利用的信息类别进行分类归纳;最后讨论了其中有待进一步开展研究的几方面工作。     

地形信息对确定DEM适宜分辨率的影响

分辨率会直接影响基于栅格数字高程模型（DEM）的数字地形分析结果,因此在实际应用中,需要选择适宜的DEM分辨率。目前采取的基本方法,基于某种地形信息定量刻画尺度效应曲线,从而确定DEM适宜分辨率,但对于采用不同地形信息时所产生的影响尚缺乏研究。本文针对该方法中通常采用的坡度、剖面曲率、水平曲率等3 种地形信息,每种地形信息提取时,分别使用两种不同的常用算法,在3 个不同地形特征的研究区中,逐一计算其在不同分辨率下的局部方差均值,以刻画尺度效应曲线,确定相应的DEM适宜分辨率,并进行对比分析。结果表明：① 采用剖面曲率或水平曲率所得适宜分辨率结果基本相同,但采用坡度所得出的适宜分辨率结果则有明显差别,后者所得的适宜分辨率更粗;② 采用不同地形信息时,越是在平缓地形为主的研究区,所得的适宜分辨率结果越相近,在复合地形特征的研究区所得到的适宜分辨率区间均明显较宽;③ 地形属性计算时所用的算法对适宜分辨率结果的影响不明显。     

Field Relationships, Geochemistry, Zircon Ages and Evolution of a Late Archaean to Palaeoproterozoic Lower Crustal Section in the Hengshan Terrain of Northern China

The Hengshan complex forms part of the central zone of the North China Craton and consists predominantly of ductilely-deformed late Archaean to Palaeoproterozoic high-grade, partly migmatitic, granitoid orthogneisses, intruded by mafic dykes of gabbroic composition. Many highly strained rocks were previously misinterpreted as supracrustal sequences and represent mylonitized granitoids and sheared dykes. Our single zircon dating documents magmatic granitoid emplacement ages between 2.52 Ga and 2.48 Ga, with rare occurrences of 2.7 Ga gneisses, possibly reflecting an older basement. A few granitic gneisses have emplacement ages between 2.35 and 2.1 Ga and show the same structural features as the older rocks, indicating that the main deformation occurred after -2.1 Ga. Intrusion of gabbroic dykes occurred at -1920 Ma, and all Hengshan rocks underwent granulite-facies metamorphism at 1.88-1.85 Ga, followed by retrogression, sheafing and uplift. We interpret the Hengshan and adjacent Fuping granitoid gneisses as the lower, plutonic, part of a late Archaean to early Palaeoproterozoic Japan-type magmatic arc, with the upper, volcanic part represented by the nearby Wutai complex. Components of this arc may have evolved at a continental margin as indicated by the 2.7 Ga zircons. Major deformation and HP metamorphism occurred in the late Palaeoproterozoic during the Luliang orogeny when the Eastern and Western blocks of the North China Craton collided to form the Trans-North China orogen. Shear zones in the Hengshan are interpreted as major lower crustal discontinuities post-dating the peak of HP metamorphism, and we suggest that they formed during orogenic collapse and uplift of the Hengshan complex in the late Palaeoproterozoic （〈1.85 Ga）.     

起伏地形下天文辐射分布式估算模型

基于数字高程模型（DEM）,建立了起伏地形下天文辐射分布式估算模型.模型全面考虑了地形因子对天文辐射的影响,只需DEM数据作为输入项,适用于遥感图像处理、地理信息系统等数据处理平台.以1km×1km分辨率的DEM数据作为地形的综合反映,计算了我国全年各月天文辐射的空间分布.结果表明：我国年天文辐射总量有明显的纬向分布特点,随着纬度的降低,年天文辐射总量由北向南增加;由于受坡向、坡度和地形遮蔽因子影响,山区天文辐射表现出非地带性分布特征.本文所提供的我国天文辐射数据产品,可作为基础地理数据供相关研究应用.     

基于MODIS的祁连山区积雪时空变化特征

利用2000-2003年日资料经8 d合成的500 m分辨率MODIS卫星反演积雪资料和数字高程模型, 借助于GIS空间分析技术, 以积雪频率和积雪盖度为监测指标, 研究分析了祁连山区整体的积雪空间分布状况及其年内变化特征, 地形对积雪的分布和季节变化的影响. 结果表明: 祁连山区的积雪分布极不均匀, 积雪主要沿山系走向成条带状分布, 呈现西段多, 东段次之, 中部和南部少, 山脊多, 山谷少的特征, 且海拔越高、 山势越陡、阴坡积雪的范围越大、持续时间越久. 累积降雪时间, 就全区而言为9月至翌年5月, 但不同高度、坡度和坡向带有所差别. 海拔4 000 m以上区域存在春、秋季两个时段的积雪补给, 而海拔4 000 m以下仅有中秋至中冬一个时段的积雪补给;坡度较平缓的区域冬季和春季为主要积雪补给期, 而坡度较陡的区域则为秋季和春季;平地和南坡积雪补给主要发生在冬季和春季, 而其它坡向为春季和秋季.     

大规模地形实时绘制算法

该文提出一种适合大规模地形实时绘制的简单高效的LOD简化算法。该算法使用一种紧凑有效的规则网格表示方法,优化网格节点的数目,减少可视化过程中的计算量,降低额外内存开销。探讨该算法相关的数据组织、视域裁剪、LOD层次选择、裂缝消除、三角形化等关键问题。实验结果表明,该算法实现简单,内存开销较少,CPU耗费小,对图形卡要求低,能够在普通机器上实现大规模地形的实时漫游。