RADAR CONTROLLED AIR SURVEY PHOTOGRAPHIC OPERATIONS IN AFRICA 1946–1952

Abstract

In 1943, the Colonial Research Committee accepted a proposal submitted by the Colonial Survey and Geophysical Committee to the effect that a Central Colonial Survey Organization should be established to undertake geodetic surveys and topographical mapping, publish the work completed, hold the required equipment and maintain the necessary records. In order that such an organization, if approved, could commence to operate as soon as possible after the end of war, a detailed scheme for same was called for by the Colonial Research Committee.     

THE SCHOOL OF MILITARY SURVEY AND ITS COURSES FOR COMMONWEALTH SURVEYORS

Abstract

On the first of January 1949 the Survey Training Centre of the Royal Engineers became the School of Military Survey. In the previous two years over fifty Colonial Survey Officers or Probationers came to the Training Centre as students on various courses. Many of these have now taken their places in the Colonial Survey Service. More students may come in the future not only from the Colonies but also from the Dominions, for just as the Military Survey courses are open to the military officers of the Dominions so are the Colonial Survey courses open to the survey students from the Dominion Governments. Some information about the School and courses may be of interest to these potential students and to many readers of this Review, and these notes have been written with the intention of providing this information     

RADAR CONTROLLED AIR SURVEY PHOTOGRAPHIC OPERATIONS IN AFRICA 1946–1952

Abstract

(a) Deployment of personnel and equipment. The areas to be photographed and the specifications of photography are laid down by the Direotorate of Colonial Surveys.     

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 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”.     

TRIANGULATION IN TANGANYIKA TERRITORY

Abstract

This is a résumé of the triangulation work completed within the Mandated Territory of Tanganyika, formerly German East Africa. The period covered includes the German Occupation down to 1915 and also the Colonial Office Administration from 1919 to the present day.     

THE YEAR 1933 IN CEYLON

Abstract

IN the absence on leave of the Surveyor General, a full Report for the Colonial Survey Committee was prepared by Mr. R. W. E. Ruddock, the Deputy Surveyor General. The Department in Ceylon covers so many activities that it would be impossible to mention here more than a few.     

THREE YEARS AND MORE OF THE RISING SUN or A COLONIAL SURVEY DEPARTMENT UNDER A NEW MASTER

Abstract

The late war has been responsible for many unusual situations—not the least of which was that of certain British Colonial Surv1ey Offices passing under the control of an Asiatic Invader, and it is thought that the story of one of them—the Survey Department of Malaya—will not be without interest to readers of this Review.     

DETERMINATION OF TAPE TEMPERATURES ON THE MEASUREMENT OF THE WANKIE AND SABI GEODETIC BASES,SOUTHERN RHODESIA (1953)

Abstract

The Wankie Geodetic Base was measured in May 1953 and the re-measurement of the Sabi Geodetic Base was also completed during the month following. For these measurements the standard “Macca” equipment was used, the gear being lent to the Southern Rhodesia Government by the Directorate of Colonial Surveys. As it was anticipated that both measurements would be made under hotter and more sunny conditions than normally prevail in England, the Directorate of Colonial Surveys suggested that the opportunity be taken of carrying out further tests in the determination of temperatures by the “resistance thermometer” as described by Messrs. Clark and Johnson of the National Physical Laboratory in their paper on the “Measurement of Temperature of Geodetic Surveying Tapes. Accordingly, through the good officesof the Director of the National Physical Laboratory, the apparatus comprising the resistance theremometer was made available for use on these two base measurements.     

TRIGONOMETRIC HEIGHTS AND REFRACTION

Abstract

In the past there has been considerable discussion on the above subject in this Review. There is a bibliography at the end of this article in which the full titles of previous articles are given. For brevity, reference to them in the following text is made by number only. Recently, Gulatee summarized present knowledge and asked how other Survey Departments dealt with this matter. Consequently, it was considered that it would be helpful to set out in detail the procedure adopted by the Directorate of Colonial Surveys for obtaining trigonometric heights, with particular reference to primary and seoondary chains and nets.     

PAPER CONTROL AND THE E.S.R.

Abstract

Readers will notice that the weight of the paper used in this issue of the Review has been substantially reduced when compared with the weight of that used in previous issues. The reason for this is the necessity for further economy in the use of paper. A reduction in the number of pages from sixty-four to forty-eight was made in the January and April numbers, but even these savings are not sufficient in themselves and commencing with the October issue the number of pages will have to be reduced still further from forty-eight to forty. However, by reducing the sizes of the margins, so as to give an increase in the actual printing area, it will be possible to include more printed matter on each page than appears at present. In addition, it is proposed no longer to print the whole of the Colonial Office List of Recent Appointments and Promotions in the Colonial Service, but only to include those parts of it that are of immediate interest to surveyors. As a result of these measures, it is estimated that the total amount of matter to appear in the forty pages will be almost the same as that now included in forty-eight.     

AIR SURVEY AND COLONIAL CADASTRAL MAPPING

Abstract

Photogrammetry, terrestrial and particularly aerial, with which the following will exclusively deal, is at the present time employed practically throughout the world for the preparation of maps to every scale. While at the time of the introduction of the system its use was limited to topographical maps, it has been extended in the last fifteen years to the production of cadastral maps. In spite of the conservative. attitude of the cadastral authorities of every country to all innovations, this method has been accepted more and more by such authorities. After the excellent pioneer work of Switzerland, which in the course of time is to produce cadastral maps of half the country (2,000,000 ha.) by means of photogrammetry, Germany, Holland, France, Italy, Spain, and other countries have followed this example, the method being employed in these countries in an ever-increasing degree for cadastral measurement. Although the decision for the use of the photogrammetric method for cadastral measurement has been made in some degree in Europe, the large Colonies, especially those of the British Empire, are still hesitant in this connexion. Investigations which follow hereunder have been made in order to ascertain how far this new method of measurement is useful for Colonial cadastral measurement.     

SURVEY FOR COLONIAL DEVELOPMENT

Abstract

The Inaugural General Meeting of the newly-formed Land Surveying Division of the Royal Institution of Chartered Surveyors was held at the Headquarters of the Institution in London on Wednesday, 14th December, 1949, when the following paper was read by Brigadier M. Hotine, C.M.G., C.B.E., F.R.I.C.S., Director of Colonial Surveys. This meeting, which is the precursor of others that are to be held in future at regular intervals, is of particular importance to surveyors since it was the first occasion on which those of them who had joined the Institution recently, but. werenot members oj any of the Committees appointed in connection with theformation of the Land Surveying Division, had been able to meet together as a separate Division of the I nstitu.tion, and thus to take their part in one of the Institution's normal activities. Brigadier Hotine's paper, together with an account of the Proceedings of the meeting, was published in the January issue of the Journal of the Institution and readers who belong to the Institution will thus already have had an opportunity of reading it. A large number of our readers, however, do not belong to the Institution, and do not see the Journal, and hence, and especially considering the special importance of the occasion and the intrinsic interest to all land surveyors of the subject with which the paper dealt, we have obtained the kind permission of the Editor to reproduce from the Journal the text of the paper and of the discussion which preceded and followed it.     

The geopotential to (14, 14) from a combination of satellite and gravimetric data

A set of2261 5°×5° mean anomalies were used alone and with satellite determined harmonic coefficients of the Smithsonian' Institution to determine the geopotential expansion to various degrees. The basic adjustment was carried out by comparing a terrestrial anomaly to an anomaly determined from an assumed set of coefficients. The (14, 14) solution was found to agree within ±3 m of a detailed geoid in the United States computed using1°×1° anomalies for an inner area and satellite determined anomalies in an outer area. Additional comparisons were made to the input anomaly field to consider the accuracy of various harmonic coefficient solutions. A by-product of this investigation was a new γ_E=978.0463 gals in the Potsdam system or978.0326 gals in an absolute system if −13.7 mgals is taken as the Potsdam correction. Combining this value of γ_E withf=1/298.25, KM=3.9860122·10 ²² cm ³ /sec ² , the consistent equatorial radius was found to be6378143 m.     

On the multivariate total least-squares approach to empirical coordinate transformations. Three algorithms

The multivariate total least-squares (MTLS) approach aims at estimating a matrix of parameters, Ξ, from a linear model (Y−E _Y = (X−E _X ) · Ξ) that includes an observation matrix, Y, another observation matrix, X, and matrices of randomly distributed errors, E _Y and E _X . Two special cases of the MTLS approach include the standard multivariate least-squares approach where only the observation matrix, Y, is perturbed by random errors and, on the other hand, the data least-squares approach where only the coefficient matrix X is affected by random errors. In a previous contribution, the authors derived an iterative algorithm to solve the MTLS problem by using the nonlinear Euler–Lagrange conditions. In this contribution, new lemmas are developed to analyze the iterative algorithm, modify it, and compare it with a new ‘closed form’ solution that is based on the singular-value decomposition. For an application, the total least-squares approach is used to estimate the affine transformation parameters that convert cadastral data from the old to the new Israeli datum. Technical aspects of this approach, such as scaling the data and fixing the columns in the coefficient matrix are investigated. This case study illuminates the issue of “symmetry” in the treatment of two sets of coordinates for identical point fields, a topic that had already been emphasized by Teunissen (1989, Festschrift to Torben Krarup, Geodetic Institute Bull no. 58, Copenhagen, Denmark, pp 335–342). The differences between the standard least-squares and the TLS approach are analyzed in terms of the estimated variance component and a first-order approximation of the dispersion matrix of the estimated parameters.     

TRIGONOMETRICAL HEIGHTS AND THE COEFFICIENT OF TERRESTRIAL REFRACTION

Abstract

Mr. A. J. Morley has contributed a series of articles in the Review (E.S.R., iv, 23, 16; iv, 25, 136 and vi, 40, 76) on the adjustment of trigonometrical levels and the evaluation of the coefficient of terrestrial refraction with a view to ascertaining how other Colonies and Dominions deal with these problems. This object is very commendable as several problems concerning both the observational and theoretical sides arise in height determinations, regarding which there is not much guidance in the usual treatises on the subject.     

Fehlertheoretische Maxwell-Boltzmann-Verteilung

Summary The probability to find an error vector in multiples of the Helmert-Maxwell-Boltzmann point error σ² δ_ij(δ_ij Kronecker symbol) is calculated. It is found that the probability is for σ39%, for2 σ86% and for3 σ99% in two dimensions, for σ20%, for2 σ74% and for3 σ97% in three dimensions. The fundamental Maxwell-Boltzmann-distribution is tabulated0,02 (0,02) 4,50.      

The use of atmospheric dispersion in optical distance measurement

The development of lasers, new electro-optic light modulation methods, and improved electronic techniques have made possible significant improvements in the range and accuracy of optical distance measurements, thus providing not only improved geodetic tools but also useful techniques for the study of other geophysical, meteorological, and astronomical problems. One of the main limitations, at present, to the accuracy of geodetic measurements is the uncertainty in the average propagation velocity of the radiation due to inhomogeneity of the atmosphere. Accuracies of a few parts in ten million or even better now appear feasible, however, through the use of the dispersion method, in which simultaneous measurements of optical path length at two widely separated wavelengths are used to determine the average refractive index over the path and hence the true geodetic distance. The design of a new instrument based on this method, which utilizes wavelengths of6328 ? and3681 ? and3 GHz polarization modulation of the light, is summarized. Preliminary measurements over a5.3 km path with this instrument have demonstrated a sensitivity of3×10 ⁻⁹ in detecting changes in optical path length for either wavelength using1-second averaging, and a standard deviation of3×10 ⁻⁷ in corrected length. The principal remaining sources of error are summarized, as is progress in other laboratories using the dispersion method or other approaches to the problem of refractivity correction.     

The free nonlinear boundary value problem of physical geodesy

Summary Within potential theory of Poisson-Laplace equation the boundary value problem of physical geodesy is classified asfree andnonlinear. For solving this typical nonlinear boundary value problem four different types of nonlinear integral equations corresponding to singular density distributions within single and double layer are presented. The characteristic problem of free boundaries, theproblem of free surface integrals, is exactly solved bymetric continuation. Even in thelinear approximation of fundamental relations of physical geodesy the basic integral equations becomenonlinear because of the special features of free surface integrals.