BATTLE SONG OF THE FAR-FLUNG SURVEYORS

Abstract

Air.—Any good Guest Night tune which happens to fit to a first order, and remains more or less in tune after subsequent orders. “Coming down the Mountain” and “Kabul River” would do.     

REFORM OF THE CALENDAR

Abstract

The majority of readers are doubtless aware of the masterly summary of the “History of the Calendar,” written for the Nautical Almanac for 193I (pp. 734–747) by Dr. J. K. Fotheringham. Most are probably also aware that the question of Calendar Reform has been considered by the League of Nations. At the Conference on Communications and Transit of 1931, October 19, the League adopted a resolution recommending a fixed Easter, but declared that “the present time is not favourable … for considering … a reform of the Gregorian calendar.” For information on the various measures of reform proposed at Geneva the works noted below may be consulted. In the meantime, pending the coming of reform—for come it will—readers may desire to.have a summary history of the question, with a statement of a solution which is of somewhat the same nature as others which have been proposed.     

MODERN INFLUENCES ON THE UNIVERSITY ASPECT OF PROFESSIONAL TRAINING IN SURVEYING

Abstract

Surveying in, the sense in which I propose to consider it this evening, is the technical term given to the science of admeasuring and delineating the physical features of the earth and of works executed or proposed upon its surface. I am in some difficulty over a precise definition which will satisfy everyone since, although “surveying” is generally understood in the English language to have the above meaning, there is a growing tendency to use the somewhat restricted term” land survey"; restricted since it implies omission of hydrographic, hydrological and other forms of measurement of natural features and of setting out. This is, of course, not so.     

THE NOMENCLATURE OF MAP PROJECTIONS

Abstract

Map Projections.—A matter that should have been mentioned in the original article under this title (E.S.R., vii, 51, 190) is the definition of a map projection. In the list of carefully worded “Definitions of Terms used in Surveying and Mapping” prepared by the American Society of Photogrammetry (Photogrammetrie Engineering, vol. 8,1942, pp. 247–283), a map projection is defined as “a systematic drawing of lines on a plane surface to represent the parallels of latitude and the meridians of longitude of the earth or a section of the earth”, and most other published works in which a definition appears employ a somewhat similar wording. This, however, is an unnecessary limitation of the term. Many projections are (and all projections can be) plotted from rectangular grid co-ordinates, and meridians and parallels need not be drawn at all; but a map is still on a projection even when a graticule is not shown. Objection could be raised also to the limitation to “plane surface”, since we may speak of the projection of the spheroid upon a sphere, or of the sphere upon a hemisphere. Hence, it is suggested that “any systematic method of representing the whole or a part of the curved surface of the Earth upon another (usually plane) surface” is an adequate definition of a map projection.     

RELAXATION AND THE CO-ORDINATE METHOD OF TRIANGULATION ADJUSTMENT

Abstract

Few, most certainly, will dispute the value of Mr Black's paper describing a method of “Systematic Relaxation”, which appeared in a previous number of this Review. At the same time, however, it seems to the writer to be only fair to readers to point out that the application of the method to triangulation adjustment is really a treatment, from a slightly different aspect, of methods that have long been established.     

RUN OF THE BUBBLE

Abstract

Old text-books in English frequently referred in very loose terms to the “run of the bubble”. The meaning of the term was often so doubtful as to leave the impression that the writers themselves had vague notions on the theory of the level; certainly they must have left the student often in a state of bewilderment. In the sense in which it was used the phrase “run of the bubble” appears to have been intended to suggest a line parallel to the directrix.     

THE CENTRE OF AFRICA

Abstract

It is not clear th at a knowledge of the position of the “centre” of any area, be it a county or a continent, serves any useful purpose, though it may, perhaps, help to define our ideas as to the shape of the area in question. Such information may take its place amongst those contents of the mind which are rather of the nature of art than of science, and minister harmlessly to our curiosity.     

THE STEREOGRAPHIC SOLUTION OF THE SPHERICAL TRIANGLE

Abstract

In the course of his stimulating and suggestive paper in your recent issue, No. ro, pp. 226–38, Mr. A. J. Potter writes on p. 233 “but there is no simple construction by which X can then be found”, and again on p. 237 “a direct construction, if there be such”. This cheerful challenge invites the construction of a circle centred on a given line, passing through a given point thereon, and touching a given circle, and I have found the lure of Mr. Potter's gauntlet as irresistible as its recovery has proved delicate. In order to shoulder responsibility and by no means to claim highly improbable originality, let me confess that the problem is new to me and the two constructions I offer are my own; I venture to hope that Mr. Potter may consider one or other of them not unworthy of his epithet “simple”, though I freely admit the aptitude of his empiric procedure to its purpose. The proofs are not long, but for fear of overshooting my welcome I offer them to anyone for the asking; and for the same reason my diagrams are small and therefore mere.     

ON THE CLASSIFICATION OF MAP PROJECTIONS

Abstract

1. Classes and Varieties. A map projection can be considered from different points of view, each such point of view representing a “class” of projections. The classes, in their turn, are subdivided into “varieties”.     

DEVIATION OF THE VERTICAL. DISCUSSION

Abstract

The following is a report of the discussion on the paper by Mr. A. R. Robbins on “Deviation of the Vertical” which was read at a meeting of the Land Surveying Division of the Royal Institution of Chartered Surveyors held on Tuesday, 12th December, 1950, and which was published in the January issue of this Review (xi, 79, 28–36).     

THE HYDROGRAPHIC DEPARTMENT OF THE ADMIRALTY: (I) HISTORY AND ORGANIZATION

Abstract

The Hydrographic Department of the Admiralty performs a number of functions appropriate to its status as an Admiralty Department but it is also responsible through its head, the Hydrographer of the Navy, for the compilation, publication and distribution to the Merchant Navy and the public, as well as to the Fleet, of Admiralty charts and of other nautical publications concerned with the safety of navigation. The latter comprise the “Admiralty Sailing Directions”, the “Admiralty Tide and Tidal Stream Tables”, the the “Admiralty List of Lights” and the “Admiralty List of Radio Signals ”.     

THE ACCURACY OF TOPOGRAPHICAL MAPS

Abstract

“Accuracy” in relation to maps is a term very frequently and widely used. Nevertheless it is hard to obtain any comprehensive precise definition of the word in this connection.     

PRACTICAL APPLICATION OF THE LAPLACE LONGITUDE-AZIMUTH RELATION TO CONTROL OF GEODETIC ANOMALIES

Abstract

1. In geodetic work a ‘Laplace Point’ connotes a place where both longitude and azimuth have been observed astronomically. Geodetic surveys emanate from an “origin” O, whose coordinates are derived from astronomical observations: and positions of any other points embraced by the survey can be calculated on the basis of an assumed figure of reference which in practice is a spheroid formed by the revolution of an ellipse about its minor axis. The coordinates (latitude = ?, longitude = λ and azimuth = A) so computed are designated “geodetic”.     

THE CONVERGENCE OF MERIDIANS

Abstract

Some publications that have dealt with the question of convergence of meridians seem, to the present writer, to be clouded with misconception, and these notes are intended to clarify some points of apparent obscurity. For instance, A. E. Young, in “Some Investigations in the Theory of Map Projections”, I920, devoted a short chapter to the subject, and appeared surprised to find that the convergence on the Transverse Mercator projection differs from the spheroidal convergence; the explanation which he advanced can be shown to be faulty. Captain G. T. McCaw, in E.S.R., v, 35, 285, derived an expression for the Transverse Mercator convergence which is equal to the spheroidal convergence, and described this as “a result which might be expected in an orthomorphic system”. Perhaps McCaw did not intend his remark to be so interpreted, but it seems to imply that the convergence on any orthomorphic projection should be equal to the spheroidal convergence, and it is easily demonstrated that this is not so. Also, in the second edition of “Survey Computations” there is given a formula for the convergence on the Cassini projection which is identical, as far as it goes, with that given for the Transverse Mercator, while the Cassini convergence as given by Young is actually the spheroidal convergence. Obviously, there is some confusion somewhere, and it is small wonder that Young prefaced his remarks with the admission that the subject had always presented some difficulty to him.     

THE LAY-OUT OF THE EAST AFRICAN ARC

Abstract

The only essential difference between geodetic triangulation and any other of the fifteen “orders” of triangulation—which were once proposed, and happily rejected, at an International Conference—is that steps are taken to secure the high degree of accuracy necessary over the large areas to be covered. Some of the steps taken to secure increased accuracy may well be used to insure economy in secondary work, as for instance the use of fewer readings of a large instrument, or the use of luminous signals in conditions of poor visibility; while any surveyor may at any time have to connect his work to a geodetic triangulation, using much the same methods.     

THE USE OF THE MAGNETIC NEEDLE ON SURVEYS IN TRINIDAD

Abstract

In Trinidad the magnetic needle is used on all secondary surveys. The term “compass surveys” was given, unfortunately, to these secondary surveys in order to distinguish them from surveys carried out in open country in the ordinary manner with the theodolite oriented by means of solar observations or by bearings obtained direct from the trigonometrical framework.     

TACHEOMETRIC SURVEYING AND THE USE OF THE DIFFERENTIAL SLIDE RULE

Abstract

In the E.S.R. No. 17 of July 1935, page 138, there appeared an article by Prof. F. A. Redmond on “The use of Even Angles in Stadia Surveying”. Since I have given this method a six-months' test in the field, using Prof. Redmond's “Tacheometric Tables” for the reduction of the measurements, the conclusions reached may be of some interest.     

THE EARLY HYDROGRAPHIC SURVEYS OF THE BRITISH ISLES

Abstract

The 200th anniversary of the publication by Murdoch Mackenzie (Senior) in May 1750 of his “Orcades, or a Geographic and Hydrographic Survey of the Orkney and Lewis Islands, in 8 maps”, is an opportune moment for a brief résumé of the contribution made by Mackenzie and his successors in the field of nautical surveying. The appearance of this work ushered in a new era in marine survey, for it was the first charting carried out in this country based on a rigid triangulation framework. The importance of this fact can further be appreciated when it is remembered that a contemporary topographic map like General Roys' famous “Map of the Highlands” begun in 1747 was little more than an elaborate compass sketch; thus under Mackenzie's influence, marine surveying at this period was ahead of its topographic counterpart.     

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.