Empire Survey Research Articles

CURVATURE AND REFRACTION TABLES FOR TOPOGRAPHICAL SURVEYS

In a series of articles published at different times in the Empire Survey, Review, the writer has stressed the utility of the slide rule in topographical work for both mapping and engineering purposes. It is his opinion that every topographical surveyor should be thoroughly conversant with the slide rule, and that there is no difficulty in teaching anyone, even with limited educational qualifications, all that is necessary about if. One advantage of its use is that the plotting-scale divisions need not represent any simple multiple or fraction of the normal units of length, but can be chosen so that the subdivisions cause no undue eye strain. This plotting scale can then be used for work on any scale, all necessary tables being calculated and constants adopted for use with it, without any extra work being required. A scale of I/250 (I foot divided into 25 main and 250 minor divisions) was found to meet the case.

INTERPOLATING FROM TRAVERSE TABLES TO SECONDS

In the Empire Survey Review, no. 4, 1932, Mr. Clendinning has described a method of interpolating from traverse tables to seconds. Below is another method, due to Prof. Nekrassov, for use with traverse tables published by him. The method is described in The Geodezist, Moscow, 1936, no. I, pp. 47–52.

INTERPOLATING FROM TRAVERSE TABLES TO SECONDS

AbstractIn the Empire Survey Review, no. 4, 1932, Mr. Clendinning has described a method of interpolating from traverse tables to seconds. Below is another method, due to Prof. Nekrassov, for use with traverse tables published by him. The method is described in The Geodezist, Moscow, 1936, no. I, pp. 47–52.

CONDITION FOR THE CONSTRUCTION OF A CONFORMAL PROJECTION

In the Empire Survey Review for October 1938 (iv, 30, 480) a simple demonstration of the condition to be satisfied for conformal representation was given. This condition may be expressed by the equation w = f(z), where w and z are complex variables representing corresponding points in the w-plane and z-plane respectively, and f(z) is an analytic function of z.

CONDITION FOR THE CONSTRUCTION OF A CONFORMAL PROJECTION

In the Empire Survey Review for October 1938 (iv, 30, 480) a simple demonstration of the condition to be satisfied for conformal representation was given. This condition may be expressed by the equation w = f(z), where w and z are complex variables representing corresponding points in the w-plane and z-plane respectively, and f(z) is an analytic function of z.

Capt. G. T. McCaw, C. M. G., O. B. E

CAPT. GEORGE TYRRELL McCAW, who died on October 17, was the editor of the Empire Survey Review and one of the foremost and best known authorities on geodesy in the British Empire.

NORMAL EQUATIONS RESOLVED BY APPROXIMATION

AbstractWe are indebted to Professor R. V. Southwell for the approximate method of computation known as the systematic relaxation of constraints. In an article to the Empire Survey Review, 1938, Mr A. N. Black showed how Southwell's ideas could be applied to the adjustment of the co-ordinates of a point.

A TEST OF AUTO-COLLIMATION

AbstractIn the July 1940 issue of the Empire Survey Review Mr A. V. Lawes contributes a valuable article, “The Application of the Gauss Method of Collimation to the Adjustment of Survey Instruments”. One section of the article describes four methods of adjusting collimators at solar focus, in other words of assuring that the emitted rays are parallel or that the target appears at an infinite distance. Mr Lawes rightly claims that auto-collimation is the most accurate of the four methods, and he warns readers that “the reflector used in this method must be as perfect optically as the objective”. However, he fails to give any method of testing the result obtained by following his directions, and experience suggests that auto-collimation may give a result considerably in error even though the reflector may with some justification be presumed to be good.

A TEST OF AUTO-COLLIMATION

In the July 1940 issue of the Empire Survey Review Mr A. V. Lawes contributes a valuable article, “The Application of the Gauss Method of Collimation to the Adjustment of Survey Instruments”. One section of the article describes four methods of adjusting collimators at solar focus, in other words of assuring that the emitted rays are parallel or that the target appears at an infinite distance. Mr Lawes rightly claims that auto-collimation is the most accurate of the four methods, and he warns readers that “the reflector used in this method must be as perfect optically as the objective”. However, he fails to give any method of testing the result obtained by following his directions, and experience suggests that auto-collimation may give a result considerably in error even though the reflector may with some justification be presumed to be good.

LATERAL DISPLACEMENT OF SIGNALS OBSERVED

I notice that in the last two numbers of the Empire Survey Review a lateral displacement is mentioned or implied.

NOTES ON THE GEODETIC SURVEY OF SOUTHERN RHODESIA

Triangulation.—Apart from Simms' Geodetic Chain, Gordon's Chain, the Copper Queen Limb, and a section of the Victoria and Umtali Series, all the primary triangulation shown on the accompanying map has been executed since 1933. The work of Simms and Gordon has been remodelled, however, being greatly strengthened, and these chains are now called Simms' and Gordon's Series. For an explanation and plan of the above Series, see “A Note on the Trigonometrical Survey of S. Rhodesia”, in the Empire Survey Review, no. 27, vol. iv.

NOTES ON THE GEODETIC SURVEY OF SOUTHERN RHODESIA

Triangulation.—Apart from Simms' Geodetic Chain, Gordon's Chain, the Copper Queen Limb, and a section of the Victoria and Umtali Series, all the primary triangulation shown on the accompanying map has been executed since 1933. The work of Simms and Gordon has been remodelled, however, being greatly strengthened, and these chains are now called Simms' and Gordon's Series. For an explanation and plan of the above Series, see “A Note on the Trigonometrical Survey of S. Rhodesia”, in the Empire Survey Review, no. 27, vol. iv.

Some Comparisons Between Theodolite Observations and Target Rifle Shooting

(1939). Some Comparisons Between Theodolite Observations and Target Rifle Shooting. Empire Survey Review: Vol. 5, No. 33, pp. 134-137.

THE TRAINING OF TECHNICAL ASSISTANTS IN MALAYA

Abstract The subject of the training of European surveyors has received a great deal of attention in the course of the last two Empire Conferences, but little or no mention has been made of the native surveyor, his education, work, and prospects. The subject is very important, however, and the account of the training of Africans for the N. Rhodesia Survey, which appeared in vol. iii, no. 21 of the Empire Survey Review, was read with considerable interest. It may not be out of place, therefore, to introduce this paper on the means adopted in Malaya to recruit and train an efficient staff of subordinates or “Technical Assistants” as they are termed locally.

STONEHENGE AND WOODHENGE

AbstractOwing to the kindness of the editor, I have recently been able to see the article on Stonehenge and Woodhenge by Captain Learmont, together with the editor's notes in the Empire Survey Review for April 1936. I hope the editor will also allow me space to make a few comments.

EVALUATION OF THE COEFFICIENT OF TERRESTRIAL REFRACTION

In a previous article on this subject (Empire Survey Review, January 1937) the writer sought to show that for trigonometrical observations of vertical angles made near noon in the Tropics the coefficient of refraction depends chiefly on height above ground level in the case of stations sited within a few hundred feet above the general level of the ground surface. Indeed, the computed values of the coefficient K show a definite and appreciable increase with “h”, the height of the observing station above ground level; it is usually assumed that K decreases with increase in height above the Mean-Sea-Level surface. From analysis of the results obtained by varying h but holding the heights above Mean Sea Level fixed the writer came to the conclusion that the variations in K could only be due to abnormal values of dt/dh and d2t/dh2, “t” denoting the air temperature. Now it is generally recognized by meteorologists that abnormal lapse-rates of temperature do frequently occur in the lower air layers in the Tropics; but up to the present time no temperature soundings in Nigeria are available. Recently, however, the writer came across the results of the aerological soundings made by an expedition in East Africa during the year 1908. The results of many of the soundings were of no use for the purpose of this paper; many of the observations were not taken at or near noon, and in others counterlapses of temperature in the lower layers indicated that conditions were not normal. A set of observations taken at Mombasa between 10 and 11 a.m. were eventually chosen as offering an example of what might reasonably occur in the lower layers of the atmosphere.

ELIMINATION OF ERRORS OF LATITUDE AND REFRACTION IN THE PAIRING OF AZIMUTH OBSERVATIONS

In a previous Article (Empire Survey Review, ii, II) I described a simple graphical method for the elimination of latitude error in observations for azimuth. It was pointed out that the ideal method of adjustment of azimuths would be a simultaneous elimination of both latitude and refraction errors and, with that in view, a purely theoretical method of such an adjustment was demonstrated in the last paragraph of the article. It has now occurred to me that a fairly simple mathematical solution is possible.

THE TRAINING OF TECHNICAL ASSISTANTS IN MALAYA

The subject of the training of European surveyors has received a great deal of attention in the course of the last two Empire Conferences, but little or no mention has been made of the native surveyor, his education, work, and prospects. The subject is very important, however, and the account of the training of Africans for the N. Rhodesia Survey, which appeared in vol. iii, no. 21 of the Empire Survey Review, was read with considerable interest. It may not be out of place, therefore, to introduce this paper on the means adopted in Malaya to recruit and train an efficient staff of subordinates or “Technical Assistants” as they are termed locally.

STONEHENGE AND WOODHENGE

Owing to the kindness of the editor, I have recently been able to see the article on Stonehenge and Woodhenge by Captain Learmont, together with the editor's notes in the Empire Survey Review for April 1936. I hope the editor will also allow me space to make a few comments.

Conference of Empire Survey Officers, 1935

Conference of Empire Survey Officers, 1935