Characteristics and landcover of estuarine boundaries: implications for the delineation of the South African estuarine functional zone

This study investigated whether the current lateral boundary for estuaries in South Africa, i.e. the estuarine functional zone (EFZ), includes all estuarine habitats. The EFZ covers 173 930 ha in 304 estuaries/outlets nationally. Field surveys and analysis of available aerial images showed that 82 (12 956.70 ha) of these estuaries (26%) had estuarine habitats occurring outside of this boundary. As a result of mapping scale, the National Vegetation Map does not represent habitats that are associated with small estuaries (approximately 50% of South Africa's estuaries). For estuaries in the Western and Eastern Cape provinces, most habitats have been lost due to urban development, whereas in subtropical areas (northern Eastern Cape and KwaZulu-Natal), cultivation has removed estuarine habitat. Although delineation of boundaries can be complicated by landcover changes, the estuarine lateral boundary in Cape estuaries could be identified based on sediment characteristics (moisture content, organic content, electrical conductivity), groundwater characteristics (salinity, conductivity and depth) and plant species. The delineation of the EFZ needs to be consistent, inclusive of all estuarine physical and biological processes, and cost-effective to identify so that it can protect estuarine habitats.     

CORS基准站周跳探测与修复方法研究

在高精度GNSS测量中,周跳的存在直接影响到整周模糊度的解算及最终定位精度。针对目前各省市连续运行基准站网多系统观测数据的获取导致周跳探测工作量增加,该文基于甘肃省卫星定位连续运行基准站网(GSCORS)双频观测值提出了一种满足普遍条件的多系统周跳探测方法。采用相位减伪距结合电离层残差法分别对GPS和BDS原始观测值进行周跳探测与修复,通过对相应载波的模拟周跳探测发现,BDS较大的卫星钟差和伪距噪声影响了数据质量,其周跳检测量时间序列波动大于GPS,对7周以上周跳探测的精度较GPS会有1周的偏差,但电离层残差法能对BDS相位减伪距法探测残留的1周小周跳进行二次探测并修复。实验最终证实该方法能够有效探测并且正确分离GPS和BDS每个频率1周以上的周跳。     

Development of a drought vulnerability index using MCDM and GIS: study case in São Paulo and Ceará, Brazil

Natural Hazards - Although climate change vulnerability research in general has increased over the last decade, Latin American countries have more directed more limited efforts toward vulnerability...     

Experimental verification of effective anisotropic crack theories in variable crack aspect ratio medium

Physical modelling of cracked/fractured media using downscaled laboratory experiments has been used with great success as a useful alternative for understanding the effect of anisotropy in the hydrocarbon reservoir characterization and in the crustal and mantle seismology. The main goal of this work was to experimentally verify the predictions of effective elastic parameters in anisotropic cracked media by Hudson and Eshelby–Cheng's effective medium models. For this purpose, we carried out ultrasonic measurements on synthetic anisotropic samples with low crack densities and different aspect ratios. Twelve samples were prepared with two different crack densities, 5% and 8%. Three samples for each crack density presented cracks with only one crack aspect ratio, whereas other three samples for each crack density presented cracks with three different aspect ratios in their composition. It results in samples with aspect ratio values varying from 0.13 to 0.26. All the cracked samples were simulated by penny‐shaped rubber inclusions in a homogeneous isotropic matrix made with epoxy resin. Moreover, an isotropic sample for reference was constructed with epoxy resin only. Regarding velocity predictions performed by the theoretical models, Eshelby–Cheng shows a better fit when compared with the experimental results for samples with single and mix crack aspect ratio (for both crack densities). From velocity values, our comparisons were also performed in terms of the ε, γ, and δ parameters (Thomsen parameters). The results show that Eshelby–Cheng effective medium model fits better with the measurements of ε and γ parameters for crack samples with only one type of crack aspect ratio.     

Exploring seismic inversion methodologies for non‐stationary geological environments: a benchmark study between deterministic and geostatistical seismic inversion

This paper presents a comparison between subsurface impedance models derived from different deterministic and geostatistical seismic inversion methodologies applied to a challenging synthetic dataset. Geostatistical seismic inversion methodologies nowadays are common place in both industry and academia, contrasting with traditional deterministic seismic inversion methodologies that are becoming less used as part of the geo‐modelling workflow. While the first set of techniques allows the simultaneous inference of the best‐fit inverse model along with the spatial uncertainty of the subsurface elastic property of interest, the second family of inverse methodology has proven results in correctly predicting the subsurface elastic properties of interest with comparatively less computational cost. We present herein the results of a benchmark study performed over a realistic three‐dimensional non‐stationary synthetic dataset in order to assess the performance and convergence of different deterministic and geostatistical seismic inverse methodologies. We also compare and discuss the impact of the inversion parameterisation over the exploration of the model parameter space. The results show that the chosen seismic inversion methodology should always be dependent on the type and quantity of the available data, both seismic and well‐log, and the complexity of the geological environment versus the assumptions behind each inversion technique. The assessment of the model parameter space shows that the initial guess of traditional deterministic seismic inversion methodologies is of high importance since it will determine the location of the best‐fit inverse solution.     

面向信息化测绘的网络化测图系统研究与应用

随着信息化测绘生产体系构建的不断深入,利用先进的信息技术对数字化测绘流程升级改造迫在眉睫,传统航测生产单机作业模式已难以满足网络化、信息化的高效生产需求。本文以武汉长江新城房屋测图为例,借助MapMatrix Grid软件进行网络化测图系统的研究和应用,论述了网络化测图生产的关键技术和生产流程,并对系统性能进行了评价。     

低空遥感在违法建筑快速监测中的应用

介绍了低空遥感平台及其数据特点,研究了其检测城市变化的方法,实现了对违法建筑的快速监测。     

三维城市地质空间数据库数据组织及模式设计

如何建立高效的数据组织以及存储模式是三维城市地质数据库必需要解决的两大基础性问题。本文通过引入基于地学属性的三维矢量数据组织方法以及基于类八叉树的真三维体数据组织方法,解决了传统海量三维空间数据无法在数据库中高效组织和访问的问题,从而在真正意义上实现了三维城市地质空间数据的数据库组织;并在此基础之上,针对城市地质空间数据的特点,提出了元数据驱动的数据存储模式,有效地增强了三维城市地质空间数据库的可扩展性和灵活性。     

利用Geoway ImageStation和SQL Server进行正射影像生产的若干问题思考

首先介绍Geoway ImageStation和SQL Server相结合的新型正射影像生产模式的产生背景,通过对全国第二次土地调查底图生产项目中正射影像制作过程中遇到的若干问题进行阐述,以及对正射影像产品质量进行分析,说明此种生产模式的优势和可行性.     

海洋声速剖面的自动聚类研究

以海区30'网格方区多年月平均统计的声速剖面作为原始数据集,提取声速剖面的表层、主跃层和深海等温层分层结构特征,把我国近海及其邻近海域预分为Ⅰ,Ⅱ和Ⅲ类区。对Ⅱ,Ⅲ类区声速剖面,应用有序样本聚类算法分别进行表层分离。根据各类区的表层声速剖面数据,通过归一化处理和Akima差值采样得到梯度剖面,建立起按月归一化后的声速剖面分层梯度样本集,并应用系统聚类法和SOFM神经网络方法分别进行聚类分析,再根据分类结果并结合各类型海区的声学特点,得到各类型海区声速剖面的典型类型。通过对大量历史数据的分析结果表明,该方法为自动分类海洋声速剖面提供了一条有效路径,弥补了长期以来海洋声速剖面主要依靠人工分类的不足。