DIRECT USE OF AIR PHOTOS FOR CADASTRAL PURPOSES IN ZANZIBAR

Abstract

Since a number of factors have combined to separate the second part of this paper from the first appearing in the E.S.R., issue No. 63, Volume IX, pp. 1–14, and written by Sir Ernest Dawson, I feel that some emphasis, already given, may reasonably be reproduced. To quote from Sir Ernest's paragraph on the Main Problem :—“The crux of the matter which I had been invited to solve, was the definition and record in a simple, sure and economical way, of the increasing number of unstable small holdings in their tangled setting throughout the Protectorate.”     

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).     

LENGTH AND AZIMUTH OF LONG LINES ON THE EARTH

Abstract

In the E.S.R., viii, 59, 191–194 (January 1946), J.H. Cole gives a very simple formula for finding the length of long lines on the spheroid (normal section arcs), given the coordinates of the end points. In the course of the computation the approximate azimuth of one end of the line is found, the error over a 500-mile line being of the order of 3″ or 4″. If the formula is amended so that the azimuth at the other end of the line is used in computing the length of the arc, the error is then less than 0″·1 over such a distance. An extra term is now given which makes this azimuth virtually correct over any distance. Numerical tests show that Cole's formula for length and the new one for azimuth are very accurate and convenient in all azimuths and latitudes.     

A NOVEL METHOD OF MEASURING THE COEFFICIENT OF THERMAL EXPANSION OF INVAR

Abstract

In a letter published in a recent issue of Nature, Prof. L. F. Bates and Mr J. C. Wilson, of University College, Nottingham, have described a new and novel method of determining the coefficient of thermal expansion of invar. Although this method is hardly likely to be applied to the measurement of the coefficient of expansion of long invar tapes, such as are used by surveyors, yet it is so novel and ingenious in itself that a short reference to it may not be out of place in this Review. One extremely interesting thing about it is that no measurements of a length, or of changes of length, are involved.     

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.     

IMPROVING THE PERFORMANCE OF WILD PRECISION THEODOLITES

Abstract

IN the July issue of the Empire Survey Review, vol. ii, no. 13, pp· 424–8, there appeared a review of precise theodolite investigations carried out by the present writers; the original papers were published in the March, 1934, number of the Canadian Journal of Research of the National Research Council, Ottawa. The elaboration of some points which could not be given much space either in the original papers or in the review may be of interest.     

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.     

TWO PROBLEMS OF RESECTION

Abstract

That admirable annual, The Surveyor (Ceylon), was generously forwarded to us some months ago. In this issue, vol. 2, no. 4, p. 93, there is given the solution of a question on resection in an examination paper. Since the solution appears rather laboured and the problem is interesting in itself and by no means valueless, it seems not out of place to attempt a simpler and more obvious answer.     

THE CLARKE FORMULÆ FOR LATITUDE,LONGITUDE AND REVERSE AZIMUTH,WITH CORRECTIVE TERMS FOR USE ON VERY LONG LINES

Abstract

This extremely simple and elegant method of computing geographical co-ordinates, given the initial azimuth and length of line from the standpoint, was published by Col. A. R. Clarke in 1880. There is no other known method giving the same degree of accuracy with the use of only three tabulated spheroidal factors. Clarke himself regarded this as an approximate formula (vide his remark in section 5, p. 109, “Geodesy”); but as this article demonstrates, it is capable of a high degree of precision in all occupied lati tudes when certain corrections are applied to the various terms. These corrections are comparatively easy to compute, require no further spheroidal factors, and some of them may be tabulated directly once and for all.     

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.     

NOTE ON THOMPSON'S ANALYSIS OF THE IMPROVEMENT RESULTING FROM THE USE OF A RESEAU IN AIR TRIANGULATION AT THE ORDNANCE SURVEY

Abstract

1. In a paper on “Some Recent Developments in Photogrammetry” which he read recently at the Royal Institution of Chartered Surveyors and which has now been published in the Institution's Journal, Lieut.-Col. E. H. Thompson, R.E., expounded the advantages of using a reseau ruled on the glass pressure plate of the camera in order to obtain a calibrated grid on each photograph.     

A TEST FOR THE RELIABILITY OF TRIGONOMETRICAL OBSERVATIONS

Abstract

I should like to reply to the Editor's comments on the above article, published in the E.S.R., v, 34, 226 (October 1939).     

SOME EFFECTS OF PULLEY ECCENTRICITY IN BASE MEASURING APPARATUS

Abstract

The comprehensive paper on the suspension of tapes by M. Hotine in the January, 1939, issue of the Empire Survey Review (v, 31, 2) did not contain any reference to this question, as was pointed out by A. J. Morley in a letter published on page 261 in the same volume (v, 34, 261). A brief analysis has been made by F. Yates of the theoretical effects of pulley eccentricity and misalignment (“Gold Coast Survey Department Records” VoL III, 1931, page 43) but I have not seen any further reference to the subject and have recently experienced the effects of such a defect in our own apparatus, so the followingnotes nlay be of interest. Before proceeding to details I will describe briefly those parts of the apparatus which are considered here and give a short summary of the whole paper.     

LONG LINES ON THE EARTH

Abstract

The Arc of the Geodesic.—In the first part of this paper a method was given for computing the azimuth of a geodesic. The method gives the convergence of the geodesic correctly up to the second power of e the eccentricity. The formula (9), however, also depends on the assumption that σ, the arc-length of the geodesic, can be obtained with sufficient accuracy from the Supplemental Dalby Theorem, that is to say, by a purely spherical computation. It is, therefore, needful to show that this supposition is justifiable; a means must in fact be indicated for verifying the assumption.     

RECIDIVISM OF COMMUNICATIVE CARTOGRAPHY UNDER THE GUISE OF AUTOMATION

The author, in a review of Ye. Ye. Shiryayev's book, Cartographic Presentation, Transformation, and Analysis of Geoinformation, addresses several issues in the automation of cartography—in particular what he perceives as a growing tendency to underestimate the importance of understanding the information being portrayed on maps. A formalistic (strictly quantitative) view of generalization that focuses on preservation or minimization of the loss of information on an initial map ignores the potential for the creation of new knowledge through the abstraction and elimination of information about lower-order systems. Salishchev criticizes Shiryayev's method of “raster digitizing” on such formalistic grounds, and because of its lack of visual quality and purported indiscriminate application within cartography. Shiryayev's reply to Salishchev's comments appears in the following paper of this issue. Translated from: Geodeziya i kartografiya, 1985, No. 11, pp. 59–61.     

NOTE ON THE REDUCTION OF CIRCUMMERIDIAN ALTITUDES TO THE MERIDIAN

Abstract

The method of reducing circummeridian altitudes or zenith distances to the meridian, using the factors m and n as tabulated by Chauvenet, is well known. The following method, which does not use these factars, has been faund both more convenient and more accurate in practice. The formula can be easily obtained by expanding m and n in powers of t, but far the sake af campleteness the derivatian is here given from the beginning.     

APPROXIMATE METHODS OF SOLVING NORMAL EQUATIONS

Abstract

My attention has recently been drawn to an article by G. H. Menzies (E.5.R., vi, 46, 474) on this subject. The present note is intended to point out improvements in the Anér method, which he favours, and to refute some of his criticisms of the Relaxation method. References are to page and table numbers in Menzies's paper.     

THE CLARKE FORMULÆ FOR LATITUDE,LONGITUDE AND REVERSE AZIMUTH,WITH CORRECTIVE TERMS FOR USE ON VERY LONG LINES

Abstract

25. A very complete exposition of the Clarke formulæ has been made in a paper entitled “Latitudes, Longitudes and Azimuths—Clarke's Method”, by G. T. McCaw, which was cyclostyled by the G.S.G.S. in 1922. In the present article the writer carries the theme a step further by indicating more fully the maximum possible values of the various small errors, tabulating them when possible, and also giving examples of the computation of long lines which require the inclusion of the various corrective terms. The formulæ for these corrective terms have been expanded to include higher power terms for investigational purposes. References are given to the page and formula number from McCaw's paper: his notation has been slightly altered, but this is fully explained in the present text. The azimuth used in the Clarke formulæ is that of the geodesic and not that of the plane curve.