海底表层底质探测系统的性能试验与评价

通过海上比对试验,对海底表层底质探测系统的主要技术性能指标进行了客观的评价。主要测试项目包括底质采样与识别、走航测量、底质识别最大深度和重复一致性等。     

中国干旱区地理水文研究概述

从水资源形成演化规律、水资源规划利用、水循环和水量平衡、新理论、新技术在地理水文研究中的应用、水资源可持续管理等方面论述了我国干旱区地理水文研究的进展。     

海洋测绘垂直基准综论

系统分析了海洋测绘垂直基准的分类及其在海洋空间信息表达中的作用,论证了现代海洋测绘垂直基准的体系模式。阐述了无缝海图深度基准的概念和实现方案、海洋测绘垂直基准的分级模式、不同级别垂直基准的相互转换关系,以及海洋测绘垂直基准的质量控制和应用。目的是推动现代海洋测绘垂直基准框架体系的建设。     

Partial polygon pruning of hydrographic features in automated generalization

This article demonstrates a working method to automatically detect and prune portions of waterbody polygons to support creation of a multi‐scale hydrographic database. Water features are sensitive to scale change, therefore multiple representations are required to maintain visual and geographic logic at smaller scales. Partial pruning of polygonal features – such as long, sinuous reservoir arms, stream channels too narrow at the target scale, and islands that begin to coalesce – entails concurrent management of the length and width of polygonal features as well as integrating pruned polygons with other generalized point and linear hydrographic features to maintain stream network connectivity. The implementation follows data representation standards developed by the US Geological Survey (USGS) for the National Hydrography Dataset (NHD). Portions of polygonal rivers, streams, and canals are automatically characterized for width, length, and connectivity. This article describes an algorithm for automatic detection and subsequent processing, and shows results for a sample of NHD subbasins in different landscape conditions in the US.     

A method to generalize stream flowlines in small-scale maps by a variable flow-based pruning threshold

The aim of this paper is to explore and describe a method of automated generalization designed to produce a map which strikes a balance between cartographic and hydrologic representations. Following a discussion of scholarly literature on generalization, we describe a novel method for automated generalization of hydrographic stream data, using the National Hydrography Data Set (NHDPlus) as an example.

Traditional hydrography shows a fairly uniform density of stream flowlines over space. While this is pleasing to the eye, traditional methods tend to under-represent rivers in humid areas and over-represent them in arid areas. We address this problem through a method in automated generalization to produce a high-quality presentation of hydrographic data, suitable for display as a wall map or in an atlas. Streams are pruned based on a variable flow threshold, derived from the local mean annual precipitation by a regression equation.

After running the model using different parameters, we produce a more satisfactory portrayal of stream networks in the United States that communicates the flow of water through rivers and reflects the regional climate. Specific advantages in generalizing with variable flow threshold include (1) the method allows for fine gradations in output scale; (2) the output maps tend to minimize density variations in the raw data; (3) the subjective criteria are easily derived; and (4) the method can be performed rapidly on large data sets, as long as the stream data has been enriched with reliable flow rates.     

Modeling Local Tidal Constituents Using TOPEX/POSEIDON SSH for the Malaysian Marine Region

A new Local Ocean Tide Model, has been produced for the Exclusive Economic Zone (EEZ) of Malaysia, which incorporates some of the latest TOPEX/POSEIDON data for the years 1992 to 1998. Local tide gauge data are used as a comparison, along with another leading Global Ocean Tide Model, Ori96. The leading diurnal and semidiurnal constituents M₂, S₂, N₂, K₁, O₁, P₁ and Q₁ are reproduced using TOPEX/POSEIDON Sea Surface Heights (SSH) in a response analysis type least squares derivation following Munk and Cartwright (1966).     

我国湿地景观研究现状、存在的问题与发展方向

湿地景观研究是近十余年来新兴的热点领域,极大地推进了湿地学科发展.但是,由于湿地景观研究体现的是湿地与景观方法有机结合,其在发展过程中还存在许多问题.本文在对我国湿地景观研究现状系统分析基础上,重点阐明了湿地景观概念、分类、遥感信息提取精度、多源数据可比性、结构与格局研究方法、景观过程与功能研究内容与尺度等制约湿地景观研究的主要问题.并指出了未来发展方向:(1)重视湿地景观分类研究;(2)重视湿地景观破碎化研究;(3)重视发展基于过程和功能的景观格局研究方法;(4)重视多尺度湿地生物多样性研究;(5)重视湿地景观管理研究.