THE CONFORMAL TRANSFORMATION OF A NETWORK OF TRIANGULATION

Abstract

In a recent issue of this Review, an example is given of the conformal transformation of a network of triangulation using Newton's interpolation formula with divided differences. While the application of the method appears to be new, attention should be drawn to the fact that Kruger employed Lagrange's interpolation formula in a discussion and extension of the Schols method in a paper which was published in the Zeitschrift für Vermessungswesen in 1896. A reference to this paper was given at the end of the paper, “Adjustment of the Secondary Triangulation of South Africa”, published in a previous issue of the E.S.R. (iv, 30, 480).     

NUMBER ONE HUNDRED

Abstract

Readers will notice that this issue of the Review is numbered 100 and, as it has always been published quarterly, this means that it has now been in existence for 25 years and so celebrates its silver jubilee.     

TRAVERSE ADJUSTMENT: WHY NOT LEAST SQUARES?

Abstract

In the above article by Mr H. L. P. Jolly published in a previous issue (E.S.R., vol. iv, no. 28) the author, after referring to the precision of the Nigerian traverses, makes the statement that measurements of the highest accuracy are worthy of the best possible methods of adjustment. But this argument cuts both ways. For in general the greater the accuracy of measurement the smaller will be the ultimate misclosure to be eliminated; so that different methods of adjustment will produce smaller and smaller variations in the corrections, until in the limit when there is no error we should obtain the same result however much latitude we permitted in the adjustment.     

Tactile Mapping: Yesterday,Today and Tomorrow

Abstract

The paper presents an overview the development of techniques in and uses of tactile mapping² through the last fifty or so years. It provides both a background for the other papers in this issue,³ and an account of the current state of the art. It notes that cartography has almost as much to learn from tactile cartography as vice versa, and suggests possible routes and areas for future developments in tactile mapping and the education and care of blind and visually impaired people.     

THE YEAR 1937 IN NIGERIA

Abstract

The year 1937 showed no diminution in the demands on the Land and Survey Department from both Government and private sources. Although there was practically no increase in staff over that of the previous two years, the output by nearly every branch showed a considerable increase on that of 1936. In April the number of super-scale posts was increased to three by the creation of the post of Principal Assistant. Nine European and two African officers were recipients of the Coronation Medal.     

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.     

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.     

ATTRACTION OF THE “COMPENSATION”: A NOTE

Abstract

The proof of the attraction of a uniformly thin vertical block in the last issue (No. 24, p. 87) does not appear as satisfactory as the textbook would suggest. It is proposed to attempt here a more direct explanation, independent of substitutional expedients.     

BOWDITCH TRAVERSE ADJUSTMENT AND A MODIFICATION: NOTES

Abstract

In the second part of the paper on this subject in the last issue (30, 483) the references to the relative angular and linear closures are rather misleading. Mr Clendinning points out that the probable angular error at a station must be considered; the mean error is clearly different.     

TRIANGULATION: BEARINGS VERSUS ANGLES

Abstract

There has always been a marked difference of opinion on the relative merits of the methods of bearings and of angles as applied to triangulation, though it is probable that the majority of writers prefer the method of bearings for first-order work. The subject was mentioned in a recent issue of this Review (vii, 47, 19).     

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).     

Unclassed Animated Choropleth Maps

Abstract

The potential of unclassed animated choropleth maps as a solution to false patterns of geographic change arising from data classification is investigated. Old concerns about unclassed choropleth maps may be mitigated through map interactivity that offers four advantages over traditional data legends, and previous insights from testing static choropleth maps do not necessarily translate to animated cartography. Data from user testing revealed unclassed animated choropleth maps neither help nor hurt the ability of map readers to understand patterns of geographic change. However, the unclassed map (1) appeared 'less jumpy' to participants and was perceived to run at a slower pace (despite running at the same number of frames per second), and (2) subtle geographic shifts (e.g., seasonal unemployment cycles) were more readily noticed on the unclassed maps. Preliminary results also suggest classed data emphasise stability over time – while their unclassed counterparts improve our ability to see changes. This paper also outlines animated simultaneous contrast as a new perceptual issue in the creation of animated choropleth maps.     

CONVENTIONS AND GENERALIZED FORMULAE FOR THE ASTRONOMICAL TRIANGLE

Abstract

In the October 1953 issue of this Review (E.S.R. xii, 90, 174), Mr. J. G. Freislich has written of the difficulties of a southern hemisphere computer attempting to use astronomical formulae from a textbook prepared for use in the northern hemisphere. He proposes a solution in which different conventions are adopted in the two hemispheres, leading to different formulae for the two cases, a solution which the present writer does not favour.     

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.     

HEIGHTS ON KILIMANJARO

Abstract

The Tanganyika Department of Lands and Surveys is to be congratulated on the successful Kilimanjaro Heighting Expedition recorded in the January 1954 issue of this Review (xii, 91, 194–210). In particular, K. T. Pugh is to be commended for his tenacity in makjng the summit observations under trying conditions.     

HORIZONTAL ANGLES IN TRIANGULATION: SOME PRACTICAL SUGGESTIONS REGARDING THEIR OBSERVATION AND ADJUSTMENT

Abstract

MR. RAINSFORD'S paper on Directions versus Angles in the Least Squares Adjustment of Triangulation in the October 1950 issue of the E.S.R. (x, 78, 353–366) has raised some interesting points and has prompted me to put on paper my own views and some of the results of my own experience.     

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