对无定向导线计算方法的分析

无定向导线计算方法较多，计算过程繁简不一，计算结果的精度也有差异。本文列举了各种无定向导线的计算方法，通过实例计算，对各种计算方法的优缺点进行一些系统的分析和讨论。     

对折迭后方交会的看法

后方交会有许多不同的计算方法。有些计算方法在交会角过小时，可以改变成折迭式计算，认为这样做的话，可以提高点位的计算精度。但又有些计算方法，如英国的安谢麦特计算式，它不能改变成折迭形计算。     

无定向导线的计算方法及其精度

本文综合介绍了无定向导线的严密平差方法、近似平差方法和概略计算方法比较了各种计算方法的精度，指出不同计算方法的适用范围。     

《基于Voronoi图的GIS空间关系计算》出版

《基于voronoi图的GIS空间关系计算》一书近日由测绘出版社出版。该书系统地评述了国内外空间关系计算的研究现状，重点介绍利用集合代数与voronoi方法进行空间关系计算的基本原理与方法。主要内容包括：国内外空间关系计算的研究现状，Voronoi图的生成算法，空间关系计算的集合代数方法框架，拓扑关系计算、方向关系计算、邻近关系计算，空间关系计算工具VTKit以及应用等。     

实验室检定航摄相机内方位元素和畸变差计算方法的比较

航摄相机内方位元素和物镜畸变差检定过程中的计算方法有很多种,本文对平均值算法、谢尔兴算法、畸变均方和最小算法、威特厂计算方法等五种主要的计算方法进行比较,评价优劣,以期找到科学的与实际相配套的计算方法。     

计算子午线弧长的数值积分法

应用数值积分原理,提出一种子午线弧长正反算的计算方法。该方法计算原理简单,计算稳定性好,便于计算机编程实现,可以达到给定的计算精度。     

介绍我们的归心和大地曲率改正计算方法

在平差计算过程中,主重的工作是概略计算与平差计算。在概略计算中,用一般方法进行归心计算,特别是视准点归心甚感不便。现在提出新的公式及其方法介绍如下：     

计算内插法传递函数的新方法

本文在对Makarovic~v计算内插法传递函数的方法进行分析的基础上提出了一种新的计算方法。结果表明,新方法不但理论上正确,而且方法简单计算速度快。     

约束Delaunay三角剖分在土方量计算中的应用

针对工程设计中传统土方量计算方法所存在的不足之处，提出了一种基于约束三角剖分网的计算方法。其主要思想是：在基于三角网计算土方量方法的基础上，结合约束三角剖分的性质，建立符合计算区域特征的约束三角剖分网，再以此为基础进行区域土方量的计算。     

基于Model Builder的土地开发整理土方量批量计算工具的研究

在土地开发整理项目的土方计算中,传统的ArcGIS计算方法需要操作者按照复杂的步骤依次进行,且每次只能计算一个田块。当田块较多时,需耗费大量时间,且容易出现错误。针对该方法的缺点,本文借助Model builder流程化建模平台,将传统的ArcGIS土方计算方法进行延伸改进,构建了土方量批量计算的模型工具,并结合具体工程实例进行验证。结果表明,土方批量计算模型工具的计算精度与传统ArcGIS方法一致,但自动化程度更高,计算速度更快,能够同时计算多个田块土方量,大大地提高了工作效率。     

THE TWO METRES: THE STORY OF AN AFRICAN FOOT

Abstract

Introductory.—From time to time the question of the relation between the metre and the foot is raised, most frequently perhaps from Africa. Had there been no more than a single metre to consider the question would no doubt arise but seldom: the most recent authoritative comparsion would be generally accepted. But actually it is the existence of two metres—the “ legal” and the “international”—which complicates the question, so much indeed that there is no metrological factor which has influenced survey, British and foreign, more than the relation between these two metres. The question was discussed in this Review (I, 6, 277, 1932), but memories grow shorter, attention is more diffused, and besides there is required a more explicit statement of the situation as it affects British surveyors, especially in Africa, whence the question has been raised anew. To illuminate it, unfortunately the need recurs to repeat some well-known facts.     

Impact of missing flow on active inundation areas and transformation of parafluvial wetlands in Punarbhaba–Tangon river basin of Indo-Bangladesh

Punarbhaba river of Indo-Bangladesh has experienced hydro-ecological alteration after installation of Komardanga dam in 1992 and consequently wetland and inundation areas have undergone into transformation. The present work intends to explore the impact of flow attenuation on contemporary and upcoming flood extent and flood plain wetlands. In post-dam condition, average and maximum flows are attenuated by 36 and 41%, respectively, and as a result the active flood prone area is squeezed considerably by 39.72%. Average flood water depth is also reduced by 37.87% (4.45metre) after flow modification. Due to shrinkages of flood prone areas, wetland area is also reduced from 215.70 to 90.40 km² and larger part of the present wetland area is under stress and critical state. Predicted flood prone areas in next 25 years will be 328.91 km² and consequently 65.63 km² wetland areas may further be under hydro-ecological threats. Release of ecological flow is essential to restore and preserve the wetland.     

北京市万米网格划分方法探讨

参考北京市东城区网格划分工作的经验,以朝阳区及海淀区为例,介绍所采用的网格划分及属性录入新方法,本方法旨在针对各区的不同情况,对城市万米网格划分进行补充性的讨论。     

AN OLD FILE AND A NEW ARC

Abstract

In his article “Standards of Length in Question” published in the last number of this Review (Vol. i, pp. 277–-84) Captain G. T. McCawgave us most interesting and valuable history concerning the questionable past of the international metre. He has, it may be assumed, exhausted published evidence; but he states that he can find no reference to invitations from this country to France and Holland to send their fundamental standards for comparison with others at the Ordnance Survey in the eighteen sixties.     

Application of GIS for land-use/land-cover change analysis in a mountainous terrain

Integration of remote sensing data with other spatial/non-spatial data was carried out using ARC/INFO software package. A simple classification technique was adopted for land cover/land-use change analyses in relation to elevation, slope, aspect and bio-climatic classes. Suitability assessment of land where agricultural extension occurred between 1963 and 1993 was made using GIS software package. Expansion of agriculture and was found to be maximum in 2200-2400 m elevation zone and 20–30° slope classes. When topographic aspects were considered expansion was maximum on south east and west facing slopes. The loss of vegetal cover is estimated to be 15 per cent between 1963–1993. However regeneration of forest was found to be maximum in elevation ranges of 1600–2000 metre and mostly having 20–30° average slope, Land deterioration over the two mapping periods was identified and strategies were suggested to mitigate the problem.     

Analysis of the heading sensitivity in the Litton inertial survey system

The straight line concept which has developed as a practical design restriction in intertial surveys with the Litton System is not only cumbersome in the planning stage but also often affects the economy of the survey adversely. A more flexible use of the system is therefore desirable. The analysis of test data taken along a well-controlledL-shaped traverse near Ottawa indicates that software modifications can eliminate a large part of the errors the to heading sensitivity. The paper discusses the design of an appropriate smoother and ways to find its model structure and its weighting from a series of test runs. Results show that the maximum standard deviation along anL-shaped traverse of100 km length is about half a metre. Further improvements are envisaged by changes in the survey procedures and a more effective use of the filter output. Optimal smoothing is not possible at present and would require a redesign of the filter output.     

Satellite remote sensing of forest type and landcover in the subalpine forest region,Kananaskis Valley,Alberta

Landsat Thematic Mapper (TM) imagery and a digital elevation model (DEM) of the Kananaskis Valley in southwestern Alberta have been used to separate three forest types and eight landcover classes with mapping accuracies up to 76% overall. Image transformations based on a principal components analysis (PCA) were used to distinguish vegetation type and separate surface features in visual interpretations, and to reduce the 10 channel data set (TM 1–7, elevation, slope and incidence) to a more manageable 7 channel data set (PCA 1–4, elevation, slope and incidence). The DEM was shown to be critical in providing explanation of surface cover variability even though the original model was produced from medium scale aerial photography on a relatively coarse 100 metre grid. Discrimination increased up to 50% for pure stands of Lodgepole Pine (Pinus contorta Dougl.) and Englemann Spruce (Picea englemanii Parry) based on analysis of 100 pixels in test areas. Overall increases in map accuracy were between 2 and 11%. Success at this level of classification is required prior to detailed ecological study and modelling of mountain vegetation productivity at the community level using current satellite and aerial remote sensing technology.     

智能手机多频多系统实时动态的定位性能分析

随着位置服务的发展,人们对定位精度的需求不断提升. 目前智能手机定位主要依赖于全球卫星导航系统(GNSS)芯片所提供的芯片解,其精度仅为米级. 2016年,谷歌宣布允许开发者获取手机GNSS原始观测数据,为研究手机GNSS高精度定位算法提供了支持. 为探索智能手机多频多系统实时动态(RTK)的定位精度和可靠性,文中基于华为P40智能手机开展了静态和动态环境下的多频多系统RTK的定位性能分析. 结果表明:在静态环境下,智能手机多频多系统的RTK定位精度要优于芯片解,在东(E)、北(N)、天(U)三个方向的定位误差均方根(RMS)分别为0.20 m、0.39 m和0.31 m,比芯片解提高了57%、71%和75%;在动态环境下的定位精度依然能够达到分米级,相比于芯片解在E、N、U三个方向上的定位精度提高了37.84%、47.22%、53.68%.      

Combining Metric Aerial Photography and Near‐Infrared Videography to Define Within‐Field Soil Sampling Frameworks

Abstract

This paper investigates the combination of metric aerial photography and near‐infrared (NIR) videography data to improve the design of field‐survey sampling frameworks. Spatial data collection can contribute up to 80% of the cost of deploying a Geographic Information System (GIS) based Decision Support System (DSS). The use of remotely sensed information, field survey using differential Global Positioning System (dGPS) and geostatistical interpolation methods maximises data quality for a given rate of sampling.

Medium‐format colour aerial photography and NIR videography were orthorectified to the national map base and mosaiced using ERDAS Imagine. The green and red layers of the aerial photography were combined with the NIR videography to form a false‐colour composite image. Two sampling strategies were tested. The first stratified sampling on a per field basis, creating four points per hectare, randomly located within each field. The second strategy used the remotely sensed information to identify within‐field variability classes for each field, using red‐green difference or normalised difference vegetation index (NDVI) models. These variability classes were used as a sub‐stratification framework with each class sampled at the same rate of 4 per hectare. For both strategies the sample points were generated within ESRI ArcView and were located in the field using dGPS. Maps of stone content were created using geostatistical methods and validated against samples collected on a 100 metre grid. It was concluded that combining the two image sources to create a within‐field stratification framework improved the precision of the results obtained from field‐survey.     

测绘工程专业人才培养计划的探讨

介绍我校制定测绘工程专业人才培养计划的基本思路及课程结构体系,总结了培养计划的基本特点,并对落实该计划在的问题进行了探讨,对测绘专业人才培养计划的制定有一定的参考意义。