ADJUSTMENT OF THE SECONDARY TRIANGULATION OF SOUTH AFRICA

Abstract

The Secondary Triangulation of South Africa consists of a uniform network of triangles of from 5- to 10-mile sides, enmeshed in the Geodetic and Primary Triangulations. As a rule the Primary Triangulation is rigorously adjusted by least squares, and the Secondary made to conform to it by an approximately rigorous method which was introduced into the Trigonometrical Survey in 1920 by the late Dr van der Sterr.     

THE STATE OF THE SURVEYS OF BRITISH AFRICA IN 1905-06

Abstract

Whilst turning over some old papers the other day I came across a copy of the first Annual Report of the Colonial Survey Committee, and the recent, much regretted death of Sir Herbert Read reminded me of his services in the development of the surveys and explorations of British possessions in Africa, especially his suggestion, which was approved by the Secretary of State for the Colonies, of the formation of the Colonial Survey Committee, an Advisory Committee which was set up in August, 1905. This Committee advised the Secretary of State “in matters affecting the survey and exploration of British Colonies and Protectorates, more especially those in Tropical Africa”.     

江苏省基础地理信息中心

江苏省基础地理信息中心隶属于江苏省测绘局,与省测绘资料档案馆、省测绘研究所是三块牌子,一套班子,实行党委领导下的行政分工负责制。主要从事基础性、前期性、公益性的测绘工作,是集测绘生产、科研、服务于一体的全额拨款事业单位。     

THE HEIGHT DETERMINATION OF MOUNT KILIMANJARO TANGANYIKA,EAST AFRICA

Abstract

The following account of the expedition which succeeded in fixing a new height for Mount Kilimanjaro is taken in the main from the diary of the party that made the necessary observations, but, for the sake of clarity, it is as well to set out here a very brief statement of the position.     

SIR DAVID GILL AND THE GEODETIC SURVEY OF SOUTH AFRICA AND THE ARC OF THE 30TH MERIDIAN

Abstract

In the memoir of the late Capt. G. T. McCaw which appeared in the January number of this Review (vii, 47,2), reference was made to the part which the late Sir David Gill played in the origin of the work on the survey of the Arc of the 30th Meridian in Africa. This year is the centenary of Gill's birth, as he was born in June 1843, and it is therefore timely to give some account of his work during his long term of office as Her Majesty's Astronomer at the Cape which resulted inthe inception and completion of the Geodetic Survey of South Africa and the survey of the Arc to the southern shores of Lake Tanganyika. He died on 24th January 1914.     

DETERMINING AND PRESENTING THE THIRD DIMENSION OF A CITY CENTRE: A PHOTOGRAMMETRIC APPROACH

The heights of buildings in the city centre of Glasgow have been measured by photogrammetric methods. A comparison of the heighting accuracy with ground checks obtained by the use of a reducing telemeter indicates the possibilities of achieving accurate results by means of photogrammetric instruments and methods. An attempt to present the third dimension of the city on paper has also been made with the Stereosimplex He and the Perspektomat coupled together to form a drawing system. It is hoped that this approach can be further developed so that it will be of use to town planners, urban geographers and others with an interest in the rapid collection of accurate data about cities.     

SOUTH AND EAST AFRICA AND THE INTERNATIONAL UNION OF GEODESY AND GEOPHYSICS

Abstract

THE resolutions and pious hopes (væux) passed by the International Union of Geodesy and Geophysics at Edinburgh in September 1936 have just been circulated in a formidable document of 8 pages and XXIX commandments. Of these, two affect the Cape-to-Cairo line particularly and they seem to deserve special study. The first of these, Number III—on systems of Projections—applies the meridional strips of the Transverse Mercator Projection apparently to all maps, topographical as well as cadastral.     

PERSPECTIVE CENTRE CO-ORDINATES: A STUDY OF CALCULATION METHODS

Various methods of calculating the perspective centre co-ordinates prior to independent model aerial triangulation are described and test results are used in the adjustment of a strip of photography in order to study the effect on residual errors. Although brief, the experiment suggests that the simplest and quickest method, involving a few grid intersection readings at one Z level, should be sufficiently accurate for normal production mapping.     

RELATIONS OF BEACON AND DEED-PLAN IN SOUTH AFRICA

Abstract

MR. C. O. GILBERT'S article on “Beacon versus Deed-plan” (E.S.R., Jan. 1932, pp. 98–99) raises a question of very great importance in those countries which have a system of land registration. In addition to the legal and technical aspects of the question, it raises the very important question of preservation of beacons and replacement of lost beacons. As he mentions the South African practice, the experience of the Transvaal may be of interest to readers, the more so as the case, The African and Buropean Investment Co., Ltd. and Others versus John Warren and Others, which he quotes, concerned farms situated in the Transvaal. I also wish to refer specially to the Transvaal, because there the diagram or deed-plan is of great legal force when there is a conflict between the position of a beacon on the ground and the position accorded it by a confirmed diagram.     

THEODOLITE TRAVERSING IN TROPICAL AFRICA

Abstract

1. In latter years a good deal has been written in English on precise traversing, both in regard to the field work and also the various methods of computation, whatever system of proj ection is used. A bibliography of publications known to the writer is given at the end of this article. But the ordinary traversing most frequently carried out by surveyors, which might be classed as secondary and tertiary, does not appear to have received the same attention in the printed word.     

PHOTOGRAMMETRIC MAPPING IN SOUTH AFRICA

Abstract

This discussion relates to the use by the Trigonometrical Survey of South Africa of Wild photogrammetric equipment in the compilation of 1/18,000 topographical maps from 1/30,000 photographs and to the accuracy of the work found thus far by field check. The equipment used, the field and compilation methods and the specifications for the work are briefly described in this article.     

THE VARIATION OF THE ATMOSPHERIC COEFFICIENT OF REFRACTION WITH THE NATURE OF THE SOURCE OF LIGHT

Abstract

In working out vertical heights on the Akuse-Kete Krachi chain of triangulation in the Gold Coast a fairly considerable difference was found between values of the coefficient of refraction obtained from observations taken during the day and those taken at night, the mean values being 0.069 for daylight observations to heliographs and 0.087 for night observations to lamps. This difference no doubt is due mainly to the condition of the atmosphere during the day differing from its condition during the night rather than to any effect due to different sources of light. A new chain has recently been observed in Western Ashanti, and the index of refraction for the daylight observations again gave a lower value than that obtained from the night observations, the figures being 0.073 and 0.099 respectively. For the night work three different sources of light were used, hurricane lamps for short lines, Tilley vapour-pressure lamps for lines of intermediate length, and McCaw acetylene signalling lamps by Watts for long lines. It occurred, therefore, to the writer to examine the results to see if the mean values of the index of refraction showed any variations for the different light sources, since it seemed reasonable to suppose that the constitution of the light emitted from each source would be different and hence that the coefficient of refraction might vary.     

ON THE ESSENCE OF THE LANGUAGE OF THE MAP

The author continues development of his concept of cartography as the “language of the map,” an earlier paper of this subject appearing in translation in M.S.R.S., 1985, No. 1. Although the term language has been widely used to describe cartographic communication, current theory fails to incorporate aspects of the language which provide for a comprehensive understanding of its structure and function. In particular, the language of the map and its symbolic elements cannot be explained reflexively by methods and rules of symbol and map design, since these elements were developed not before but after the existence of the language. The language of the map thus is proposed as the mechanism which provides for replicability or duplication in the way a system of mapmaking-map use functions (under diverse conditions, purposes, historical periods, and levels of training of users) through its different methods, models, and norms. Translated from: Geografiya i prirodnyye resursy, 1985, No. 3, pp. 142-151.     

THE THEORY OF THE ANALYTICAL SOLUTION OF THE STEREOGRAM

The theory of the solution of the stereogram is developed from the condition that the vector triangle, formed by the base-line and the two rays from the perspective centre to a common model point, shall be in equilibrium. Using this approach the unique definition of a point in the model follows naturally from the solution of the relative orientation problem.     

THE CALCULATION OF THE HEIGHT OF KILIMANJARO

Abstract

The observations to height Kilimanjaro were made from two ground stations, Domberg (5,081·6 ft.) and Lelatema (5,323.1 ft.) and from a point called Kibo near Kaiser Wilhelm Spitze which is regarded as the highest point on the crater rim. It was originally intended to include a third ground station, Kifaru, but it was discovered that the ice cap obstructed observations between this point and the top.     

试论地图形式美的规律

本文从六个方面阐述了地图形式美的规律性,最后进一步说明了其规律性与增强地图美感的关系。