SOME NOTES ON ASTRONOMY AS APPLIED TO SURVEYING

Abstract

Astronomy is not a subject that is taught much from text-books, and the excellent but rather out-of-date books such as Chauvenet and Ball do not contain many of the more modern methods. The writer, as a one-time professional astronomer, has been able to pick up various ideas about the sort of astronomy useful to surveyors, with which some surveyors may not be familiar and which might be useful to them. The whole of these notes are not entirely his own work, many of the details having been first suggested by the late Dr. L. J. Comrie, F.R.S.     

CLAUDE REIGNIER CONDER (1848–1910) AND THE SURVEY OF PALESTINE

Abstract

Few surveyors can have been set a more interesting task than that which fell to the lot of Claude Conder, who first thoroughly explored and mapped the Holy Land some seventy years ago. His work is still of value, and must be referred to by all who are concerned with the ancient topography and archreology of that country. It may be found interesting to consider exactly what the task was, how it was accomplished, and something of the career of the young man who successfully carried it through.     

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.     

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.     

THE ORTHOMORPHIC PROJECTION OF THE SPHEROID–III

Abstract

In the last instalment we were able to obtain most of the surveyor's projections in common use by applying simple scale conditions to the meridians and parallels. This method of approach naturally suggests that results of some value might be obtained by applying similar conditions to the plane co-ordinate lines. If we do so, we are immediately led to consider curves on the surface known as geodesics, which are the nearest approach to straight lines it is possible to draw on a curved surface. Accordingly, we give some account of these curves for the benefit of surveyors who have not hitherto made their acquaintance.     

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.     

REWEBBING DIAPHRAGMS WITHOUT TEARS

Abstract

Every student of Close and Winterbotham's “Text Book of Topographical Surveying” learns that rewebbing diaphragms is a simple job. Unfortunately, when circumstances compel a surveyor to reweb a micrometer diaphragm in the field, he is liable to find, after some years in the tropics, that fever (and one thing and another) have played havoc with the steadiness of hand and eye. Under present conditions young surveyors who have been trained on optical micrometers may find themselves using 5″ micrometer theodolites with over a dozen webs, anyone of which is liable to sag, break or develop whiskers, while even a “Tavi” may conceivably remind the user that it has one web.     

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.     

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.     

A SIMPLE PROPOSITION lN,TRIGONOMETRICAL SURVEY AND ITS USES

Abstract

1. The proposition which expresses in terms of the three sides the rate of change of the angle at the vertex of a triangle whose base is stationary and whose vertex is given a small displacement is an important one in plane survey. It must have beeJ1.known to some surveyors for a century or more but there is no doubt that even to-day it is not widely known. This, too, in spite of its extreme simplicity, which makes it, once known, impossible to forget. It's discoverer is unknown to the writer, who was somewhat intrigued to discover it for himself about 25 years ago in the course of field operations of the kind described in § V hereafter. The probability is that many people have discovered it independently.     

FINANCIAL CRISIS AND SURVEY—A UNITED STATES PRECEDENT

Abstract

It generally happens that, when trade is bad and there is a sharp drop in the revenue of a country such as to necessitate immediate economy, one of the first of the public services to be affected is survey; and, of all the different branches of surveying, the one that suffers most is usually the trigonometrical surveyor its equivalent. This is in spite of the fact that, taking the long view, the tdgonometrical survey is perhaps the most fundamental of all. The trouble is, of course, that it is very difficult for the non-technical individual or official to appreciate the importance of the work—indeed, it is doubtful if all surveyors realise this.     

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.     

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 TWO METRES: THE STORY OF AN AFRICAN FOOT

Abstract

Introductory.—From time to time the question of the relation between the metre and the foot is raised, most frequently perhaps from Africa. Had there been no more than a single metre to consider the question would no doubt arise but seldom: the most recent authoritative comparsion would be generally accepted. But actually it is the existence of two metres—the “ legal” and the “international”—which complicates the question, so much indeed that there is no metrological factor which has influenced survey, British and foreign, more than the relation between these two metres. The question was discussed in this Review (I, 6, 277, 1932), but memories grow shorter, attention is more diffused, and besides there is required a more explicit statement of the situation as it affects British surveyors, especially in Africa, whence the question has been raised anew. To illuminate it, unfortunately the need recurs to repeat some well-known facts.     

THE TRAINING OF AFRICAN SURVEYORS IN NIGERIA

Abstract

Whenever the Government wants to receive new students to be trained as surveyors for the Government Service it is usual for the public to be informed by means of a Gazette Notice outlining the conditions of entry into the Survey School which is attached to the Land and Survey Department. Nowadays students are admitted through the Government Higher College at Yaba by means of the Entrance Examination of that college. It is one of the conditions that before a candidate applies to take this Entrance Examination he must have passed his Cambridge School Certificate Examination, the Matriculation Examination of any British University, or its local equivalent, and must possess also a certificate of character.