GEODETIC SIGNALS IN SOUTHERN RHODESIA

Abstract

So much has been written in the Empire Survey Review and other publications on the somewhat controversial subject of “Luminous or Opaque Signals in Geodetic and Primary Triangulation” that it may be of interest to give an outline of the types of signals used on such work in Southern Rhodesia, with particular reference to the completion of the Eastern Geodetic Circuit in 1935 and the type of signal that it has been decided to adopt for future work.     

TRIGONOMETRICAL LEVELLING ACROSS THE INLAND ICE IN NORTH GREENLAND

Abstract

As part of the scientific work of the British North Greenland Expedition (1952–1954), a programme of trigonometrical levelling was carried out from the east to the west coast of Greenland, along a line across the inland ice between latitudes 76° 40′ N., and 78° 10′ N. The primary purpose of the work was to determine accurately the heights above sea level of a series of gravity stations, the gravity measurements being made in connection with determinations of ice thickness. For meteorological purposes it was necessary to know also the altitude of the Expedition's central station, situated in latitude 78° 04′ N., longitude 38° 29′ W. The accuracy necessary for the purpose of the gravity survey was a few metres for the altitudes, while the latitude of each gravity station had to be determined with an accuracy of ± 0.1 minute.     

NOTES ON GEODETIC WORK IN THE GOLD COAST

Abstract

The Gold Coast, including that portion of Togoland which is mandated to Great Britain, comprises an area of 91,843 square miles lying between the parallels 4° 45′ N. and 11°N. and the meridians 1° 10′ E. and 3° 10′ W. The greater part of the southern area is covered with dense forest, but in the north the forest gradually opens out to more open “orchard-bush”, while in the extreme north the country consists of rolling plains covered with tall elephant-grass.     

光电测距三角高程测量在山区代替三,四等水准的可行性探讨

本文作者根据自己在工作实践中的尝试，对在山区用光电测距三角高程测量代替三、四等水准问题，谈了几点体会．     

郑州市ZZCORS系统坐标联测数据的处理与分析

利用地壳运动观测网络工程的基准站为框架点,解算了七个ZZCORS站和九个GPS等级控制点的CGCS2000地心坐标,并对计算结果的精度进行了分析。     

GEODETIC BEACONS

Abstract

Mr. Clendinning's article on “Signal Lamps” (E.S.R., vol. ii, pp. 15–18) raises a point of major importance in geodetic triangulation. I entirely agree with him that the sole use of heliographs—heliostats to the purist—is in most parts of the world out of date. I also think, and indeed am prepared to state categorically, that the use of acetylene lamps is out of date and was out of date many years ago. The Americans, who are always worth listening to on the economics of surveys, would not otherwise have replaced all their acetylene gear by electric beacons. The answer, in my experience, and for reasons which I shall endeavour to make clear, is generally, but not necessarily always, to provide both helio and electric lighting; but first I should like to summarize the conditions in which luminous signals should be used at all.     

THE LEVELLING OF A THEODOLITE

Abstract

A Fully equipped theodolite is provided with plate levels, an alidade level, and a striding level. An instrument not so equipped has no title to be considered a “Universal Instrument”, that is to say, an instrument designed for every kind of both terrestrial and celestial measurement. Without a striding level, for example, nothing beyond relatively rough astronomical measures can be expected in general. Modern instruments, capable of giving considerable refinement in terrestrial measures, are frequently not furnished with a striding level; and it is sometimes assumed, with the tacit approval of the makers, that such instruments are equally capable of giving refined astronomical results. On the older type of instrument a striding level—rarely not supplied—could have been, and sometimes was, extemporized; it seems as if ignorance of astronomy of position has led, at least in part, to the construction of theodolites in such a manner as actually to render such extemporization difficult.     

THE ADJUSTMENT OF A FIRST-ORDER LEVELLING NETWORK

Abstract

In the E.S.R. January and April numbers of 1955, Vol. xiii, Nos. 95 and 96, Mr. Hsuan-Loh Su described the “Adjustment of a Level Net by Successive Approximations and by Electrical Analogy”. It does not seem to be as generally known as it should be that the rigid least square solution can be greatly simplified by utilizing the electrical analogy and solving by Kirchhoff's method. The method as detailed below has been in use for over 40 years.     

THE EARLIEST GEODETIC TRIANGULATION

Abstract

WILLEBRORD SNEL VAN ROIEN, the “learned Snellius,” was born in 1580 at Leyden, where his father Rudolf was Professor of Science. He naturally proceeded to the university, and made such rapid progress under his tutor, L. van Ceulen, that he was already in 1600 delivering lectures on Ptolemy's “Almagest.” With his mind developed by travel in Europe, including a residence of some duration at Prague, where he was associated with Tycho Brahe before that great observer's death in 1601 and with the still more eminent Kepler as another of Brahe's pupils, he had acquired such scholarship as to publish in 1608 a daring reconstruction of the defective work, “De sectione determinata,” by Apollonius of Tyana. This was the year of his marriage to Maria de Lange, daughter of the Burgomaster of Schoon.     

空间网联合处理中地壳运动参数的引入

本文阐述了空间大地网联合处理中的地壳运动模型的建立方法，并在此基础上提出了非均匀形变，均匀形变，体应变和刚体转动的识别方法，文中以我国现有空间大地网的模拟数据，结合中国大陆地壳构造进行了试算。     

方差分量估计理论及其在整体大地测量中的应用

本文探讨了整体大地测量平差中的方差分量估计问题,给出了自适应最小二乘配置;不仅较好地解决了各类观测量权比的确定问题,而且能够确定信号的方差因子。此外,文章还对如何更好地确定局部地区扰动位及其泛函的协方差函数作了讨论;最后通过对一个实测网进行了整体平差,并与经典平差结果进行了比较。     

MAPPING MOUNT KENYA

Abstract

Air-photo cover of the Aberdare and Mount Kenya areas was obtained for the Directorate of Colonial Surveys in February 1947 by 13 Squadron R.A.F., flying Mosquito aircraft at an altitude of 27,000 feet and navigating by visual methods.     

THE ANTI-SHIMMER LEVEL AND LEVELLING STAFF

Abstract

The object of the instrument and special staves is to enable levelling observations to be carried on in conditions of heat-shimmer which would hinder or prevent work by the ordinary methods. The instrument can, however, be used as an ordinary level in normal conditions. The staves for use with the instrument are marked with main bull's-eyes at intervals of 10 cm. and smaller intermediate bull's-eyes at the half-intervals (5cm. from each main bull's-eye). These intervals can be replaced by English units, if desired, and the reverse faces can also be marked with ordinary graduations for use in clear and steady conditions.     

NOTE ON LEVELLING UP THE PLATE

Abstract

1. The explanation of this fundamental operation in setting up surveying instruments, as well as of the theory of the level on which it is based, is, in my opinion, not sufficiently explained in text-books. I came across the problem while lecturing on the theory of surveying instruments. Below is an extract of the notes I made on the subject, which may have a didactical interest.     

关于精密水准测量中因瓦标尺的温度改正问题

标尺误差是精密水准测量的一项重要误差来源。其中由于温度变化而引起因瓦带的长度变化,是使用因瓦标尺带来的误差之一。国内外有关文献曾对此进行过深入的研究。我国过去在精密水准测量时,未测定所用因瓦标尺的综合膨胀系数,故在一等水准网平差中未对观测高差加标尺温度改正。本文主要针对将要开始的精密水准复测,讨论标尺的温度改正问题和我们的试验结果。     

GPS水准测量在高速公路高程控制测量中的应用研究

本文在介绍高程异常确定方法的基础上,着重讨论了几种ＧＰＳ高程几何拟合方法的数学模型,并通过广惠高速公路ＧＰＳ及水准测量数据,分析比较了这几种方法的精度,得出了一些有益的结论。