数字城管基础数据库多尺度表达技术探讨

针对数字城管基础数据库多尺度表达的需求和缩放可视化中出现的问题,在研究二维电子地图的多尺度表达方法的基础上,提出并设计了基于分级显示的数字城管数据库多尺度表达技术。它将数据库中的各类数据进行有规则的分级,使其在不同的比例尺下显示出来。该文以宝鸡市为例进行了数字城管基础数据库多尺度表达的实验,结果证明基于分级显示的数字城管基础数据库多尺度表达技术是可行的。     

最平滤波器在分析月平均潮位资料中的应用

应用数字滤波方法来消除验潮资料中的高频扰动而分离出海平面的趋势性变化，并设计了最平滤波器；对其幅频响应特性和相位特性的验证表明，最平滤波器的技术性能基本上是可靠的。应用最平滤波器对月平均验潮序列进行低通数字滤波，可以有效地消除验潮资料中的高频扰动，分离出低频变化。从数值计算过程、高频扰动机制及实测验潮资料的估算结果来看，低通数字滤波在确定海平面长期变化趋势中，对消除高频扰动的影响是非常重要而有效的。     

DSM-1数字旋转磁力仪技术改进的一种方法

本文介绍的DSM-1数字旋转磁力仪技术改进的方法,是经不断试验、反复修改而成的。实际应用表明:技术改进后的DSM-1数字旋转磁力仪控制系统,其性能及使用功能比原系统有较大的提高,开发的软、硬件适用于所有兼容微机。对进口的DSM系列数字旋转磁力仪控制系统进行技术改进,均可参照此方法进行。     

Automated trinocular stereo imaging system for three-dimensional surface wave measurements

A novel automated trinocular stereo imaging system (ATSIS) is developed for non-intrusively measuring the temporal evolution of three-dimensional wave characteristics. The system consists of three progressive digital cameras to provide three independent stereo-pairs, i.e. left–right, left–center, and center–right, for accurately estimating depth of a scene. A third camera assists to resolve correspondence problems due to specular reflection on the water surface and provides additional constraints on image matching, dramatically reducing the chance of a mismatch. An oblique configuration for the trinocular system effectively increases spatial coverage, allowing observations of wave phenomena over a broad range of spatial scales. The height resolution is increased with the optical axes of the cameras pointed at an oblique angle with respect to vertical surface wave displacements. A new exterior calibration procedure is developed in this paper to determine the orientation of cameras in the field. Field experiments demonstrate that ATSIS can robustly measure hundreds of matched image points in seconds, allowing fast extraction of the temporal evolution of a three-dimensional surface wave field.     

Estimation of surface chlorophyll on an exposed mudflat using digital colour-infrared (CIR) photography

The usefulness of field-based digital Colour-InfraRed (CIR) photography to quantify concentrations of chlorophyll on the surface of exposed mudflats is investigated. Multiple images, each 626 mm by 467 mm, were acquired during Austral summertime using a Duncantech three-band CIR camera from two areas of mudflat in the upper reaches of Sydney Harbour. Sediment samples were obtained from within the field of view of the camera and their chlorophyll concentration was estimated spectrophotometrically. After the camera images were normalised to compensate for the effects of variations in the intensity of downwelling solar radiation, chlorophyll was estimated for each 0.9 mm square pixel using a suite of five different vegetation indices. Regression analysis was used to determine the strength of the relationship between the index values and the estimates of chlorophyll from the in situ samples. Indices constructed from near-infrared and red bands were found to have the strongest relationships with in situ chlorophyll estimates (R² ranging from 0.28 to 0.79) and indices derived from near-infrared and green bands the weakest (R² ranging from 0.16 to 0.22). The vegetation indices highlighted complex small-scale variability in chlorophyll distribution that was not evident in the original camera images. These findings indicate that field-based CIR photography will provide a useful tool for the non-destructive determination of benthic chlorophyll.     

海上地震系统低频响应与电缆噪音

海上勘探地震采集的数据中低频率成分常常受到外部环境噪音的严重干扰。如何有效地剔除噪音 ,拾取更多的地震数据中低频成分。本文从分析地震仪器低频响应入手 ,得出了地震系统与电缆噪音的一些内在联系 ,就如何有效地压制外围环境噪音等问题 ,提供了有效的方法 ,为野外作业提供参考     

双通道实时数据采集处理系统的设计与实现

本文提出了一种基于 TMS32 0 C31串行接口的双通道实时数据采集处理系统的设计与实现方案 ,该设计以 TMS32 0 C31和 TL C32 0 AD5 0 C为核心器件 ,具有两个独立的 A/D,D/A通道 ,能够实现 32位浮点计算和 16位数据采集与回放。应用该系统进行归一化最小均方误差 (Normal-ized L east Mean Square,NLMS)算法实时自适应噪声抵消实验 ,实验结果表明 ,该系统能够实现实时的自适应噪声抵消 ,可广泛应用于实时语音信号处理等领域。     

High‐resolution mapping of Manawatu palaeochannels

New remote sensing techniques, such as airborne laser scanning (LiDAR), have led to a dramatic increase in terrain information, providing new opportunities for landform analysis. A major advance in using LiDAR‐derived high‐resolution topography (HRT) is the capability to provide an accurate and detailed terrain morphology. This study aims to use LiDAR HRT to identify palaeochannels of the Manawatu River (New Zealand) using an automated procedure based on the statistical analysis of landform curvature. The approach can provide rapid assessment and classification of floodplain topography. The proposed analysis is crucial, especially for intensively used floodplains requiring effective flood management and mitigation.     

Accessing Australian geodynamic information: The AGCRC website

The Australian Geodynamics Cooperative Research Centre (AGCRC) website <http://www.agcrc. csiro.au/> provides the main integrated presentation of the results of AGCRC research. It hosts a systematic presentation of project summaries, publication abstracts, regionally organised geodynamic syntheses and a GIS database containing a large number of broad‐scale earth science datasets from the Australian region, which are presented through an interactive map viewer. Effective interfaces are required to make the variety of content accessible to users. In particular, maintaining effective hyperlinking for a large and growing set of pages was a significant challenge. We found that by developing effective indexing tools we were able to apply a uniform technology to attack these problems. The index included both the full text of the pages from the website and also specific index terms of metadata. The metadata schema was designed to support both generalised discovery through a search interface and also to allow hyperlinks to be included automatically in pages by the server, so that the user could browse in a richly cross‐linked framework. It was necessary to manage textual and numeric data within the same framework because even the textual documents were generally tied to geospatial locations identified by their geographical coordinates. This required extensions to standard index and search tools, including the development of complete new indexing software. To assist the user in accessing the index, we provided a variety of user interfaces specialised for different themes in the website. For example, publication lists are generated in a conventional layout, and geospatial datasets are presented through an interactive map viewer and query system. The latter also demonstrated how visualisation tools for geospatial data can be provided in the web‐browser interface.     

Estimation by photogrammetry of the glacier recession on the Cotopaxi Volcano (Ecuador) between 1956 and 1997 / Estimation par photogrammétrie de la récession glaciaire sur le Volcan Cotopaxi (Equateur) entre 1956 et 1997

Abstract

Aerial photographs of the Cotopaxi Volcano ice cap dating from 1956 to 1997 were used to quantify the evolution of the surface area. Results were obtained using precise stereoscopic methods that give the most accurate information. In addition four specific glacier tongues were investigated in detail to measure the ice mass lost between 1976 and 1997. Surprisingly, the bedrock morphology is shown to be very irregular and this explains a large extent of the variability found in the ice losses. The results show that glaciers stagnated from 1956 to 1976 and lost about 30% of their surface area between 1976 and 1997. Slope exposure did not seem to have any significant effect since all the glaciers of the volcano retreated in the same proportion. In accordance with specific measurements performed on the nearby Antizana 15 Glacier, it is suggested that the strong recession observed after 1976 was associated with increasing melting conditions which have occurred repeatedly during the intense/long-duration warm ENSO phases.