大地重力学的新进展

介绍了当前利用卫星探测地球重力场的技术及其实践,也就是目前采用的高轨卫星追踪低轨卫星技术(hl-SST)、低轨卫星追踪低轨卫星技术(ll-SST)、卫星重力梯度测定技术(SSG),及其相应的正在运行的CHAMP、GRACE、GOCE卫星和考虑发射的GRACEFollow-On卫星。运行的三颗卫星所提供的地球重力场信息不论在精度和分辨率方面都是大地重力学的一个重大进展。介绍了地形数据在构建地球重力场模型中的作用和美国SRTM对全球地形数据的测量。最后介绍了EGM2008与我国已有大陆重力值的比较,平均差值约为11mgal,与我国大陆现有的高程异常值的比较,平均差值为27cm左右。     

Geodynamic framework of large volcanic fields highlighted by SRTM DEMs: Method evaluation and perspectives exampled on three areas from the Cameroon Volcanic Line

This study is a part of a wider investigation to evaluate how much can be learnt by using low-cost methods such as systematic moderate-resolution remote sensing to map and quantify geological structures at the regional scale on very large volcanic provinces only partly studied in the field. Volcanic-centre and cinder-cone distribution, faults and structural lineaments are mapped combining Shuttle Radar Topography Mission (SRTM), Digital Elevation Models (DEMs) and Landsat satellite images. As an example of the method, we present the interpretation of structural data and morphological features of three contrasted areas from the Cameroon Volcanic Line (Tombel graben, Upper Benue valley, and Ngaoundéré area) for which local field studies are available for comparison. At a local scale, this remote-sensing method of mapping displays good to excellent correlations with previously published data and, by itself, it allows one to constrain the structural setting of each area. Numerical treatment of vent and cinder-cone localisation can be related to tension fractures (T direction), whereas numerical treatment of the lineaments constrains the associated fault system to a single transtensional (strike-slip + extension) Riedel type fracture network. The first results on the Cameroon Volcanic Line are promising and could be used at a larger scale on numerous volcanic provinces for which field data are not yet available.     

适于大规模地形分析的计算格网应用

摘总结前人在GIS领域应用格网的理论和实验基础上,使用GlobusToolkit3构建DEM计算地形因子的格网服务(CSED),适用于大洲规模的DEM地形分析,并能够通过Web发布计算结果。基于此格网系统,进行了ShuttleRadarTopographyMission(SRTM)数据在地形因子自动化提取方面的计算实验。这些计算由于依赖的计算环境的重大变化,所体现出来的效率性能等方面有了很大的变化。本文选取中国青藏地区的地形数据进行了详细试验,并对实验区数据和GTOPO30的计算结果进行了对比分析。     

Morphological analysis of the Sudd region using land survey and remote sensing data

An analysis of the vast wetland of the Sudd swamps in southern Sudan was designed to assess and describe interdependencies between morphology and hydrology. Findings based on field survey and remote sensing data include an assessment of the effect of ground slopes and morphological features on spill and flooding of the seasonally flooded grasslands. Through bathymetric surveys and analysis of Landsat images, depth profiles and cross‐sectional depth and flow distributions were established. Data from remote sensing, field survey and historical sources were correlated and correction factors established; the SRTM was found to be partly unsuitable for further assessments. Further analysis of remote sensing data was used to investigate the Sudd's inland delta as well as the question of spill into the Bahr el Ghazal basin. Copyright © 2008 John Wiley & Sons, Ltd.     

Application of globally available,coarse-resolution digital elevation models for delineating valley bottom segments of varying length across a catchment

The worldwide availability of digital elevation models (DEMs) has enabled rapid (semi-)automated mapping of earth surface landforms. In this paper, we first present an approach for delineating valley bottom extent across a large catchment using only publicly available, coarse-resolution DEM input. We assess the sensitivity of our results to variable DEM resolution and find that coarse-resolution datasets (90 m resolution) provide superior results. We also find that LiDAR-derived DEMs produce more realistic results than satellite-derived DEMs across the full range of topographic settings tested. Satellite-derived DEMs perform more effectively in moderate topographic settings, but fail to capture the subtleties of valley bottom extent in mild gradient, low-lying topography and in narrow headwater reaches. Second, we present a semi-automated technique within ArcGIS for delineating valley bottom segments using DEM-derived network scale metrics of valley bottom width and slope. We use an unsupervised machine-learning technique based on the k-means clustering algorithm to solve a conundrum in GIS-based geomorphic analysis of rivers: the delineation of valley bottom segments of variable length. The delineation of valley bottom segments provides a coarse-scale entry point into automated geomorphic analysis and characterization of river systems. © 2020 John Wiley & Sons, Ltd.     

顾及数据配准的江西省SRTM DEM精度评价和修正

目前,ICESat/GLAS是大尺度SRTM DEM精度评价的主要数据源.然而,现有的精度评价方法均忽略了2组数据的有效配准.为此,本文分析了数据配准前、后SRTM DEM整体精度差异,以及不同地形因子和土地利用类型对SRTM DEM影响程度.在此基础上,充分考虑SRTM DEM精度影响因素,分别借助多元线性回归(ML...     

基于EGM2008和SRTM模型确定的新疆地区似大地水准面及其精度评估

基于EGM2008重力场模型(2190阶)和SRTM数字高程模型,在Molodensky理论框架下,确定了新疆地区15′×15′似大地水准面,并与新疆地区15个点位的实测GPS/水准数据进行了比较,结果表明,所确定的新疆地区15′×15′似大地水准面的精度约为0.2m。     

不同地形高程数据对青海夏季气温和降水模拟准确度的影响

基于SRTM 90 m、USGS 30 s地形高程数据及青海气象台站实际海拔高度数据,分析了采用不同高度数据对青海地区2014年夏季气温和降水模拟准确度的影响.采用国家基本观测站的气象观测资料对模拟结果进行检验,结果表明:相对于台站实际海拔高度,模式地形总体偏高,青海南部和祁连山区海拔较高地区及青海东部地形梯度较大地区...     

The Kufrah paleodrainage system in Libya: A past connection to the Mediterranean Sea?

Paillou et al. (2009) mapped a 900 km-long paleodrainage system in eastern Libya, the Kufrah River, that could have linked the southern Kufrah Basin to the Mediterranean coast through the Sirt Basin, possibly as long ago as the Middle Miocene. We study here the potential connection between the terminal part of the Kufrah River and the Mediterranean Sea through the Wadi Sahabi paleochannel, which may have constituted the northern extension of the lower Kufrah River paleodrainage system. New analysis of SRTM-derived topography combined with Synthetic Aperture Radar images from the Japanese PALSAR orbital sensor allowed the mapping of seven main paleochannels located west of the Kufrah River, each of which is likely to have formed a tributary that supplied water and sediment to the main paleodrainage system. The northernmost four paleochannels probably originated from the Al Haruj relief, a Pliocene alkaline basaltic intracontinental volcanic field, and potentially connected to the Wadi Sahabi paleochannel. The remaining three paleochannels are in the more southerly location of the Sarir Calanscio, North-East of the Tibesti mountains, and barely present a topographic signature in SRTM data. They end in the dunes of the Calanscio Sand Sea, forming alluvial fans. The most southern paleochannel, known as Wadi Behar Belama, was previously mapped by Pachur (1996) using LANDSAT-TM images, and was interpreted by Osborne et al. (2008) as representing part of an uninterrupted sediment pathway from the Tibesti mountains to the Mediterranean Sea. Processing of SRTM topographic data revealed local depressions which allow to connect the seven paleochannels and possibly the terminal alluvial fan of the Kufrah River to the Wadi Sahabi paleochannel, through a 400 km-long, south-north oriented, paleocorridor. These new findings support our previous hypothesis that proposed a connection between the lower Kufrah River in the region of the Sarir Dalmah and the Wadi Sahabi paleochannel, which connected to the Mediterranean Sea. Including the newly mapped paleochannels, the Kufrah River paleowatershed, at its maximum extent, would have covered more than 400,000 km², representing close to a quarter of the surface area of Libya.     

利用卫星资料反演区域冰川冰量变化的尝试——以祁连山为例

物质平衡是衡量冰川“健康”状况的最好方式,由于野外工作开展难度大,物质平衡观测仅局限于少数几条冰川上,限制了区域冰川物质平衡和冰量变化的评估.通过卫星高程数据可以监测区域冰川高程变化,进而可估算其冰量变化.利用SRTM和ICESat激光测高数据反演了祁连山冰川冰量变化,结果表明:21世纪初祁连山冰川处于物质亏损状态,年平均高程减薄(0.345士0.258)m,相当于(0.293土0.219)m w.e.,估算祁连山冰川年均冰量损失为(534.2±399.5)×106 m3 W.e..由于祁连山各冰川区相对独立,相隔较远,冰川规模普遍不大,且ICESat地面轨迹在中低纬度分布稀疏,使得结果的不确定性还很大.