SOME NOTES ON COMPUTING

Abstract

The article that follows is a collection of notes on various aspects of computing, some of them rather elementary, which it is thought might be of interest to some surveyors. Most land surveyors spend quite a lot of time computing and many become expert at it, but even so they rarely reach the stage when they cannot usefully pick up hints from professional computers. It is therefore hoped that it may be useful to collect a number of points which the writer sometimes found helpful to surveyors during the time when he was doing arithmetic for a living.     

DETERMINATION OF AZIMUTH AND LATITUDE FROM OBSERVATIONS OF A SINGLE UNKNOWN STAR BY A NEW METHOD

Abstract

The purpose of this paper is to describe a new and easy method of determining the (astronomical) latitude and azimuth at any place and to explain the line of approach and the formulae. It will be seen that the method should be useful to a wide circle of land surveyors. One of its principal advantages is that identification of the star is not necesssary and it can be used when no star chart or star catalogue is available.     

THEODOLITE TRAVERSING IN TROPICAL AFRICA

Abstract

1. In latter years a good deal has been written in English on precise traversing, both in regard to the field work and also the various methods of computation, whatever system of proj ection is used. A bibliography of publications known to the writer is given at the end of this article. But the ordinary traversing most frequently carried out by surveyors, which might be classed as secondary and tertiary, does not appear to have received the same attention in the printed word.     

THE AFRICAN ARC OF THE 30th MERIDIAN

Abstract

This project, which is now well known to surveyors not only in Africa but all over the world, was first visualised by Sir David Gill, who for many years was H.M. Astronomer at the Cape Observatory. It is fitting to commence by giving in his own words his conception of the work, the part of which from South Africa to the Equator has now been completed. The following extracts are taken from the paper “On the Origin and Progress of Geodetic Survey in South Africa, and of the African Arc of Meridian”, by Sir David Gill,K.C.B., F.R.S.     

SEMIGRAPHIC FIXATION ON A CURVED SURFACE

Abstract

The commonly known methods for semigraphic fixation of trigonometrical stations depend on rectangular coordinates and bearings computed therefrom, but the extension of such methods to cases in which the distances are so great that second-order terms in coordinate differences become appreciable is never undertaken on account of the heavy computations involved. The following method, which is not found in the ordinary text-books, may be of interest to some surveyors not only because it can be applied to fixations using triangles of any size, but also because it can be employed to fix points in a triangulation that has been adjusted but not coordinated, since it is quite independent of coordinates and bearings.     

A RESECTION METHOD

Abstract

This is a variation of the well-known device of successive approximations. It was first used by the writer about 15 years ago on a Seismic (Geophysical) Survey when resections were continually employed to locate Shot Points and Geophonestations set on arcs of 10 to 15 miles radius. Speed was an important factor, and the normal text book methods of resection were very tedious. As far as is known the method is original. It is now used by many surveyors, and the writer trusts it will be of use to others. The method is easy to remember as it has no set formula and does not involve any elaborate geometrical construction.     

THE REJECTION OF OUTLYING OBSERVATIONS

Abstract

The object of this article is to help surveyors and computers to decide whether one of several measurements of the same quantity ought to be rejected or not. No new theories are developed, but some explanation is given as t9 how the mathematical theory of statistics may be applied to measurements made in surveying.     

Mapping Everest

Abstract

From its inception in the middle of the 19th century, the Royal Geographical Society (RGS) took a keen interest in the exploration and mapping of the Everest region. This formed an integral part of the many Everest expeditions, some of which had individual surveyors or survey parties attached to them. Many mountaineers took part in this work, particularly those with a scientific background. But it was not until 1961 that a comprehensive map was produced of the Everest region.     

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.     

THE RADIAL LINE ASSUMPTION

Abstract

It is very many years since the Radial Line method was first used in America and England, and, so far from going out of favour, as was predicted by some European surveyors, it is now thriving in the Slotted Template form. The history of the method is an example of the Anglo-Saxon genius for persevering in a practical compromise. Had we been tempted by the voices of the photogrammetric Rhine Maidens to adopt theoretically exact methods to solve all problems, virtually no new mapping would have been carried out during World War II and many thousands of square miles of sparsely populated territory in the U.S.A. and British Commonwealth would still remain unmapped. A much greater mapped area is associated directly or indirectly with such names as Bagley and Hotine than with others more familiar at international conferences.     

A NEW METHOD FOR THE ADJUSTMENT OF A NETWORK OF TRIANGULATION

Abstract

A problem frequently encountered by surveyors in carrying out a system of triangulation, is the adjustment of a network of lower order triangulation to make it geometrically consistent with an existing triangulation of a higher order. For example, in Fig. 1 it will be assumed that the positions of the stations A, B, and C have already been determined and that it is now required to determine the positions of the stations a, b, c, d, e and f from the measured values of the internal angles of the network of triangulation shown. In practice, several different solutions have been suggested, ranging from rigorous least squares methods to semi-graphical solutions. The method described in this article is believed to be original and may prove of interest to surveyors.     

SURVEYS FOR TITLE

Abstract

One frequently sees suggestions that all surveys for title purposes should be connected to the geodetic framework. These come most frequently from geodesists, and the utility of a geodetic control for land-titles surveys is sometimes used as an additional argument in favour of the institution of such work in areas not yet subject to accurate control. I think few surveyors will be found in opposition, certainly not the writer.     

LEAST-SQUARE SOLUTIONS WITH A CALCULATING MACHINE

Abstract

A Calculating machine may be used merely as a substitute for logarithms to perform the multiplications and divisions in a long computation. This is possibly the commonest use to which a machine is put by the majority of surveyors. Although a great saving of time is so obtained, the full potentialities of the machine are not realized until its fundamental properties are understood. In this article one very simple property of all modern calculating machines is used to develop a method for carrying out least-square solutions.     

EVOLUTION OF LAND RECORDS

Abstract

Owing to delays at this end in the preparation of the paper on “The direct use of vertical photographs in Zanzibar for cadastral purposes”, for which apology is due to Mr. Chambers as well as to readers, its publication has been regretfully deferred. We are using the opportunity to publish the Bibliography which could not conveniently appear with our opening paper last April, and to accompany this with an outline of some early and feudal developments in land records which we hope may help to interest a wider circle of land surveyors in this feature of cadastral work. For experience in many countries has impressed on us that the effective record of rights and duties pertaining to land, particularly in parts of the world less stably patterned agriculturally and more closely divided than England, has suffered grievously from a divorce between the legal and the technical aspects of cadastral record and between its operation and effects as sought on parchment in legislatures and the administrative offices of governments and as realized in daily practice by landholders and cultivators on the ground itself.     

Mapping Palestine and Mesopotamia in the First World War

Abstract

The survey and mapping activities which took place in Palestine and Mesopotamia during the First World War need to be considered in their contexts, both of long-term British mapping activities in the region, and of survey and mapping generally during the First World War. Thus, while it is important to recognise the real technical advances in map-making which resulted from survey activities in the Near and Middle East during the First World War, it needs to be recognised that this was simply the culmination of nearly 80 years of British military mapping in the region. Each generation of surveyors used the most appropriate tools for the task in hand and the conditions under which the survey needed to be conducted. The First World War surveyors were fortunate that a new tool, aerial photography, had become available just prior to the war.