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.     

THE PERU-BOLIVIA BOUNDARY COMMISSION 1911–13

Abstract

That Peru should have drawn from the British Army the technical personnel for the survey in connexion with her boundary demarcation with Bolivia is interesting, because at this period she employed missions of French officers both for her army and for her navy. Her neighbours—certainly Chile and Bolivia—looked to Germany for instruction in military matters. Militarily England has had little connexion with Peru's development. The fact that between the capital Lima and its port Callao there stands a statue to an Englishman, a general, whose memoirs are to be found in the War Office library and who fought to win the independence of Peru from Spain, can hardly have been sufficient reason for the selection of British military officers to do her boundary work. The effectiveness of the work of Colonel Sir Thomas Holdich on the Chile-Argentina frontier was certainly a leading reason for this choice; but it is probable that the excellent work in survey and exploration accomplished for Bolivia by Lieut.-Colonel P. H. Fawcett, R.A., was the ultimate factor which decided Peru to seek in the British Army an officer of equal rank with him to serve her interests in the cause of frontier demarcation, while Fawcett was serving those of Bolivia. Fawcett's most outstanding piece of exploration had been done on this frontier a year or two before the boundary commissions assembled, and this was his ascent of the Heath river from mouth to source. During this ascent he sowed the seeds of friendship with the.natives of this river, although he was assailed by them with a flight of arrows when struggling up the river with his canoes.     

THE CADASTRAL SURVEY OF EGYPT, 1879–1907

Abstract

It may be recalled that when Lyons accepted the responsibility for the execution of the Cadastral Survey and its compilation within the time limit set by the Commissioners of the Public Debt, this was subject to the stipulation that a properly balanced land. survey organization should be established and entrusted with all land survey operations of a national character. We are now faced with the dilemma that within the limits of this paper we can neither adequately examine nor leave unconsidered the implementation and effect of this stipulation, upon which the success attained, both in the immediate objective and in the ultimate perpetuation and extension of its benefits, vitally depended. Lyons's critical difficulty, which reacts on us here, resembled having to take charge of a rumbling old wagon which could not be stopped, but had to be rapidly converted as it went, into a well-powered lorry. We think our best course will be to review briefly (i) in the order of their original institution the principal parts of the Departmental machine that Lyons gradually built up and (ii) the processes by which their united effect in the field enabled the task for which the Department had been founded to be achieved.     

THE CADASTRAL SURVEY OF EGYPT, 1879–1907

Abstract

Repercussions to Failure (1883–96).—So far we have only had occasion to consider the primary fiscal objective of the abandoned cadastral survey; but during the decade devoted to it (1879–88) other public activities had been developing which were no less dependent upon detailed maps for their effective and equitable operation. Pre-eminent among these was the irrigation service. During the previous part of the century various spasmodic efforts to construct general maps of the country had produced little more than a series of conventional diagrams, on scales of I : 100,000, or 200,000, depicting the approximate positions of the main waterways and villages throughout the Delta and Valley against a blank background. But it was upon knowledge of at least the broad pattern of cultivation, waste and marsh, of surface level and incline, throughout the countryside, that the satisfactory planning and operation of the interrelated system of supply and drainage channels depended; while the only regular means of accumulating this knowledge had been the abortive survey. For crude and unreliable as its work was and useless for its intended purpose, that survey had been providing for the first time village by village in important districts an interpretable picture of these broad effects. The Irrigation Service did its best to fill the gap by setting up a survey section to prepare a “hydrographic map” of Lower Egypt to meet its own requirements. The staff were mainly drawn from the disbanded cadastral survey and the methods used are reported to have been essentially the same; but the simpler character of the work evidently fostered certain changes. As the network of property boundaries was ignored the map scale was reduced of 1 : 10,000 and the plane table became the principal instrument of detail survey; and since villages were no longer working units continuous map sheet series were adopted for each province. This accentuated the need for a common basic framework; but the defects of such triangulation as existed appear, however, to have been accepted and extended, some of the more obvious gaps being patched with traverse. So the detail must have been subjected to a good deal of Procrustean treatment. Nevertheless, supplemented where necessary by lines of levelling, the work constituted an indispensable reconnaissance series for irrigation.     

THE GEODETIC LEVELLING OF CEYLON (1926–1929)

Abstract

The Net.—The total length of the lines of the level-net is roughly 2400 miles. The net comprises 27 circuits with perimeters varying between 74 and 268 miles, and is generally closer in the wet zone than in the sparsely populated and undeveloped dry zones. In 12 circuits there are differences of level exceeding 1000 feet. The highest point reached in the net is 6572 feet, and a branch line runs from Nuwara Eliya to the summit of Pidurutalagala, the highest mountain in the island (8282 feet).     

THE ART OF ORIGINAL CIRCULAR DIVIDING (1650–1850)

Abstract

The problem of dividing the circle into equal parts has occupied the minds of astronomers and instrument makers from the earliest times, but little is known of the methods adopted by such renowned observers as Hevelius or Tycho Brahe, who are said to have divided their own instruments (I). It is possible, however, to trace the various steps by which progress was made and to appreciate the urgent need that was felt, particularly throughout the eighteenth century, for improvement in the accuracy of astronomical instruments, if only to satisfy the increasing demands for navigational charts and for the means of determining the position of a ship at sea.     

SOUTHERN RHODESIAN MILITARY SURVEYORS IN THE WORLD WAR, 1939–1945

Abstract

The part played by Southern Rhodesian Military Surveyors in The World War, 1939–1945, would have been comparatively simple to chronicle had the “Home” and “Away” Southern Rhodesia Survey Units formed early in the War continued as separate entities until the end of hostilities. As the narrative will show, however, in order to make the best use of the personnel available they were grouped together with surveyors from other territories into composite units and, in addition, some were employed on purely General Staff duties. Accordingly the narrative is divided into chapters covering areas–cum–periods.     

SOUTHERN RHODESIAN MILITARY SURVEYORS IN THE WORLD WAR, 1939–1945

Abstract

For some two months prior to the formation of the two companies, an intensive course of survey training and “refreshing” had been undergone by all ranks in the field sections, culminating in a combined Royal Artillery/Royal Engineer survey exercise from 1st to 10th October, carried out under operational conditions in all respects (even down to a 30-hour non-stop period of “photo-topo” compilation for the map on which the “final shoot” took place).     

THE ATTRACTION OF THE “COMPENSATION” ON THE PRATT HYPOTHESIS

Abstract

In the last issue there was given an outline of modern theories on crustal equilibrium. The assumption as to uniform attenuation of matter beneath an elevated station suggests that an explanation of a means for calculating this “compensation” would be desirable; the complete technical procedure used by those actually engaged on work of this nature could be described by themselves alone.     

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.     

WORK OF THE CADASTRAL SURVEY AND LAND RECORDS OFFICE, 1932–45

Abstract

On the occasion of the Empire Survey Conference in 1931 we had the privilege of arranging at the Science Museum an Exhibition of Cadastral Maps and Land Records which had been somewhat hurriedly collected from the United Kingdom, the Dominions, India, eleven Colonies and Protectorates, three Mandated Territories and six foreign countries. As there is some vagueness in the application in English of the French word cadastre, it may be advisable before proceeding to say that while in Europe this word, with its German and Italian equivalents, originally applied to a record of landed property (biens fonds) compiled for fiscal purposes and is commonly still so defined in standard dictionaries, we have throughout used it in the wider sense it has gradually been assuming generally of any analogous record concerned with subdivisions of land occasioned by human use, whether the purpose to be primarily served is fiscal, juridical, economic or otherwise. Cadastral survey is the process by which the parcels of land dealt with are defined, and can be located again at need. The noun, which is rarely mentioned in English, was from the earliest days applied to the whole conspectus of the record: registers, maps, supporting documents, etc. We use the term land record loosely, and somewhat unsatisfactorily, in this comprehensive sense because the more convenient and exact one-cadastral record-has not so far found a place in British practice with its associates: cadastral maps and cadastral survey.     

THE ORTHOMORPHIC PROJECTION OF THE SPHEROID—IV

Abstract

We now turn to a question which has received much attention of recent years; the possibility of transforming angular and linear field measures to an orthomorphic projection so that the results of a survey may be computed directly in plane Co-ordinates without having to go through the spheroid at all. Initially, orthomorphic projections were introduced into surveying practice for this very object. Over short lines they import so little distortion of angles that minor surveys, whose error of angular measurement is comparable with such distortion, may be reduced in the rectangular co-ordinate system of an orthomorphic projection just as if the earth were flat. But the present application goes far beyond that. We no longer ignore distortions of angles and lengths, but systematically introduce them into the field measures so that work of higher precision and of considerable extent may also be computed and adjusted in plane co-ordinates.     

THE ORTHOMORPHIC PROJECTION OF THE SPHEROID—II

Abstract

The reader will play this round better if he remembers to bring the bag of clubs provided in the last instalment. On the assumption that he will do so, we proceed straight to the first tee without further explanation or recapitulation.     

THE ORTHOMORPHIC PROJECTION OF THE SPHEROID—V

Abstract

To complete the picture, the reader is invited to plough through the derivation of point-to-point working formulae for the remaining projections in common use. The entire field of modern geodetic practice in this subject will then have been covered, and at least as simply, without the usual recourse to the square root of negative numbers or other complex notions.     

THE COMPUTER—A COG IN THE SURVEY MACHINE

Abstract

1. Lest any reader should be put off by assuming from the title of this article that it would contain a mass of technical matter, it may be stated at the outset that no computations whatever are involved. In fact it is a collection of very ordinary observations pertaining to the efficient functioning of the computing section of a Survey Department. In the opinion of the writer nothing clarifies one's ideas more than sitting down at a table and putting them actually on paper. Things that might otherwise have been overlooked or forgotten are brought to light, and can then be given their proper place in the whole mosaic. There is probably nothing original in this article, yet it is hoped that a comprehensive survey may be of assistance to other computers, as the making of it certainly has been to the writer. It has been written from the point of vievvof a computing section, rather than that of an individual computer. Each individual computer is a cog in the computing machine, whose duties are more those of routine calculation by methods approved by his superior.     

THE TECHNIQUE OF QUASI-LOSSLESS COMPRESSION OF THE REMOTE SENSING IMAGE

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THE CAPE BAR “A” AND THE METRE-FOOT RELATION

Abstract

The Cape Bar A has two sets of end marks. One set is represented by small dots in embedded surfaces of gold, and the other by finely engraved lines near the dots. The distance between the dots was measured in British units by Sir George Airy in 1839, and at the Ordnance Survey in. 1844; and the lines were standardised in international metres by M. Benoit at Paris in 1886. By lueasuring the small distances between the dots and the lines, and using the data of the original standardisations, it has been possible to obtain a value of the metre-foot relation. The ratio thus obtained agrees with the determinations of Benoit (1896) and Sears (1928).