TRAVERSING WITH THEODOLITE AND CHAIN

Abstract

As Mr H. F. Rainsford (E.S.R., no. 37, vol. v, July 1940) says, the ordinary accurate survey traverse, through its “ordinariness,” has been neglected in the printed word. The technique—perfected by much practice—has been handed down by word of mouth only from father to son, from surveyor to pupil.     

SILTING AND ISLAND GROWTH IN THE ZAMBEZI NEAR LIVINGSTONE

Abstract

The Northern Rhodesia Survey Department recently carried out a series of measurements of certain cross-sections of the Zambezi in the vicinity of Livingstone. The stretch of river over which the above were made is that known as the Regatta Course and extends between the top of Loando or Long Island downstream to the mouth of the Maramba River. This stretch is about three and a half miles southwest of Livingstone and two to four miles upstream from the Victoria Falls.     

THE ANTI-SHIMMER LEVEL AND LEVELLING STAFF

Abstract

The object of the instrument and special staves is to enable levelling observations to be carried on in conditions of heat-shimmer which would hinder or prevent work by the ordinary methods. The instrument can, however, be used as an ordinary level in normal conditions. The staves for use with the instrument are marked with main bull's-eyes at intervals of 10 cm. and smaller intermediate bull's-eyes at the half-intervals (5cm. from each main bull's-eye). These intervals can be replaced by English units, if desired, and the reverse faces can also be marked with ordinary graduations for use in clear and steady conditions.     

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.     

THE HUNTER SHUTTER EYEPIECE FOR LONGITUDE AND AZIMUTH

Abstract

The shutter eyepiece is a device for eliminating the effects of personality in observations involving the timing of a moving star crossing graticule lines. It is of importance in longitude observations and in any mixed observations involving timing of star passages over cross-lines—vertical, horizontal or oblique.     

DIRECTIONS AND ANGLES IN A SIMPLE CHAIN

Abstract

Mr. Rainsford's article on “Least Square Adjustments of Triangulation: Directions versus Angles” in the Empire Survey Review No. 78, Vol. x, October 1950, leads to many speculations and interesting results. I try to show here, how, by assuming artifices to simplify the results, weights may be assigned to angles derived from directions so that the results of adjustment by angles, with these weights, will be the same as the adjustment by directions, all of equal weight.     

FIGURES AND FANCIES

Abstract

I may say at once that this article has nothing to do with either the Gaiety chorus or the “Old Firm”: it is merely a statement of what seem to me the fancies in Dr. de Graaff Hunter's paper “Figures of Reference for the Earth”, E.S.R., No. 8,pp. 73–8. Many readers of the Review will share my gratitude to Dr. Hunter for his lucid presentation of the theory underlying the usual geodetic processes. I disagree with only one of his points, and its implications, but unfortunately that point is fundamental.     

TEMPERATURE MEASUREMENT AND SURFACE CHAINING FOR CADASTRAL PURPOSES

Abstract

The measurement of the temperature of a measuring band or bar has always been a major problem. A considerable a.mount of experimentation has been done on the morepreciseaspects of survey measurement, and attempts, ranging from packing measuring bars in ice to bimetallic apparatus, made to reduce temperature errors. At the present time electro-resistance thermometers are being used and an entire new field is being investigated using various waves for distance measurement. For at least some time in the future, however, these new techniques will not be sufficiently developed to be of practical or economic use to the cadastral surveyor. Nevertheless very much less interest is taken in what may be termed “bread and butter” procedures.     

SOUTH AND EAST AFRICA AND THE INTERNATIONAL UNION OF GEODESY AND GEOPHYSICS

Abstract

THE resolutions and pious hopes (væux) passed by the International Union of Geodesy and Geophysics at Edinburgh in September 1936 have just been circulated in a formidable document of 8 pages and XXIX commandments. Of these, two affect the Cape-to-Cairo line particularly and they seem to deserve special study. The first of these, Number III—on systems of Projections—applies the meridional strips of the Transverse Mercator Projection apparently to all maps, topographical as well as cadastral.     

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.     

THE SURVEYOR AND THE POLITICIAN: AN AFRICAN OBJECT-LESSON

Abstract

THE surveyor usually finds his employment to be an instrument wielded for military ends or in the furtherance of civil administrative policy and of those economic interests which are built upon security and good government. But he can often lend valuable and sometimes invaluable assistance in the framing of policy. The delimitation of interterritorial boundaries is one of the more obvious undertakings in which failure to enlist technical advice is liable to lead governments into grave and irreparable errors. The same considerations apply to the evolution of a land-settlement policy, and a moral may be pointed from a comparison of two such policies which have at different periods been adopted in the Uganda Protectorate.     

SARAWAK LANDS AND SURVEY DEPARTMENT

Abstract

Financial.—The revenue collection for the year was 479,591.75, consisting of Lands and Survey Revenue 356,087.52 and Mining Revenue 123,504.23.     

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     

INTERPRETATION AND ADEQUACY OF COMMONLY GIVEN INFORMATION ABOUT THE INSTRUMENTAL PRECISION OF AIR SURVEY EQUIPMENT

Abstract

Some difficulties in interpreting the specifications of instrumental accuracy are pointed out and traced to inadequate information. The paper discusses the possibility of amplifying this information for the benefit of the user and without over-burdening the inspection departments of the manufacturers.

It is suggested that the given information should include (1) estimates of all suspected errors and distortions, (2) the confidence limits relevant to (a) the errors incurred in any given measurements and (b) their point-to-point variation.

Confidencelimits for the effects of observational errors may be worked out from the t-distribution in the usual way, or more readily read from graphs given in this paper. Further research is however needed to investigate the statistical behaviour of other sources of variation in order to establish appropriate systems for the construction of corresponding confidence limits.     

ON OBSERVATIONS AND ADJUSTMENT

Abstract

The subdivision of methods of adjustment of observations as given in textbooks is usually asfollows: (1) The method of direct observations; (2) The method of indirect observations; (3) The method of conditioned observations.     

THE EFFECTS OF ECCENTRICITY AND MISPLACED INDICES OF DIVIDED CIRCLES

Abstract

Special precautions are taken in the workshop to ensure that divided circles are so mounted that the point from which the circle graduations radiate lies accurately on the axis about which rotation of the circle and reading index or indices takes place. If, through some accident, eccentricity is present, it is still possible to obtain accurate readings if the instrument is used to the best advantage, and the object of the following notes is to assist the surveyor to this end. It will be found that errors arising from eccentricity can be made to cancel out, except in the case of a vertical circle fitted with a single reading index.     

STONEHENGE AND WOODHENGE

Abstract

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.     

AN OLD FILE AND A NEW ARC

Abstract

In his article “Standards of Length in Question” published in the last number of this Review (Vol. i, pp. 277–-84) Captain G. T. McCawgave us most interesting and valuable history concerning the questionable past of the international metre. He has, it may be assumed, exhausted published evidence; but he states that he can find no reference to invitations from this country to France and Holland to send their fundamental standards for comparison with others at the Ordnance Survey in the eighteen sixties.     

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.