THE POST-WAR PROGRAMME OF THE ORDNANCE SURVEY OF GREAT BRITAIN

Abstract

In 1938 the committee to investigate the activities of the Ordnance Survey, presided over by Lord Davidson, issued its final report. One of the terms of reference of this committee was “to review the scales and styles of Ordnance Survey maps placed on sale to the public and to recommend whether any changes are desirable”.     

IMPROVEMENTS IN REPRODUCTION METHODS OF THE ORDNANCE SURVEY

Abstract

The following six notes describe some of the ways in which reproduction methods of the Ordnance Survey have recently been improved. They have been written by different officersof the Ordnance Survey and Ministry of Supply whose initials appear at the end of each note.     

THE WORK OF THE ORDNANCE SURVEY OF THE IRISH FREE STATE

Abstract

Up to 31st March 1922, the work in Ireland with regard to the revision and supply of Ordnance Survey Maps was governed by similar rules to those existing at the Ordnance Survey of Great Britain. No changes were made in the Irish Free State until the revision of Co. Waterford was completed on the 25-inch scale in 1923. It was then decided to depart from the usual procedure of taking up the work of the revision of Counties according to a cycle of years, and to revise those particular portions of the country in which extensive alterations had been carried out by reason of the division of properties by the Congested Districts Board and the Irish Land Commission. Accordingly, those portions of Counties Galway, Mayo and Roscommon which had undergone the greatest development were taken up for revision. In all eighty-nine sheets were specially revised and completed by 1928.     

THE USE OF AIR PlIOTOGRApHS BY THE ORDNANCE SURVEY

Abstract

During the last year, the Air Survey Section, Field Division, Ordnance Survey, have had many visitors. Most of them have been surprised at what they have seen: some at the fact that we are able to make so much use of air photographs even in the largest scale surveys, and some at the small amount of information we seem able to extract from them. This paper is an attempt to give in some detail the ways in which air photographs are used to solve the problems of the Ordnance Survey, why they are used and their limitations for our purposes.     

AZIMUTH COMPUTATION IN THE OLD PRINCIPAL TRIANGULATION OF THE BRITISH ISLES

Abstract

The old Principal Triangulation of Great Britain and Ireland is a classic, both in execution and publication. The names of many of those who planned it, made it possible, carried it out or computed it have become legendary in the Ordnance Survey. Such are Roy, Dalby, Ramsden, Mudge, Colby, Drummond, Steele, O'Farrell and, greatest of them all, Clarke.     

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.     

UNITS OF LENGTH AND AREA,III

Abstract

In two papers on this subject (v, 34, 236, and vi, 40, 85) some difficulties were examined and missing evidence explored. Reference was made to the past existence of divers acres in the British Isles. In a lecture by Professor A. E. Snape, M.SC., on “Our Units of Measurement”, delivered at the University of Cape Town and printed in the South African Survey Journal (III, Part viii, 24, 340, 1930), some other units are considered and additional evidence adduced. For example, the Cheshire acre is given as 2.11 statute acres.     

THE TOWN PLANS

Abstract

The town plans in question are those ranging from the “five-foot” (1/1056) to the modified “ten-foot” (1/500) scales, made by the Ordnance Survey between 1841 and 1894, and then, in principle at any rate, abandoned. This is, I fear, wholly a British matter and profuse apologies are offered to oversea readers. Yet history, repeating itself as usual, may presently add the wider interest to the tale.     

COMPILATION OF THE LAND REGISTER OF ENGLAND AND WALES

Abstract

Skillfully as those charged with the shaping and conduct of the crowded time-table of the Conference of Commonwealth Surveyors in 1947 managed their difficult task, physical inability to squeeze many good gallons’ measure into a pint pot relentlessly closured discussions and allowed no opportunity to collect and appraise the yield in any vat on the spot. We were very sensible of these effects in relation to our own and other papers on Land Registration. Our own paper too—owing to transient circumstances which overlapped the Conference—had to be presented in the stodgy form of a synopsis and—through accidents of travel—only reached some delegates, whose comments were particularly desired, on the eve of its presentation. Nevertheless the generous reception accorded to this and other ‘papers on the subject and the many stimulating points that were raised in their discussion, limited though this was, call’ for further consideration and digestion if the resultant lessons are to be elicited and put to practical use. We have, therefore, sought the approval of the Editor of this Review to pursue this purpose, so far as space permits, in this and later numbers. Our remarks should be read in conjunction with the relevant portions of the Proceedings of the Conference which are in the press but are not expected to be available for some months yet. We have especially in mind the observations of the following speakers: Mr. G. H. Curtis, Chief Land Registrar, H.M. Land Registry, London; Mr. John Dewar, previously Surveyor-General of Malaya; Mr. R. G. Dick, -Surveyor-General of New Zealand; Lt.-Col. Elkington, Divisional Officer, Ordnance Survey Office, London; Mr. F. M. Johnstone, Surveyor-General of the Commonwealth of Australia; Mr. E. A. Malby, Chief Superintendent Mapping Branch, H.～. Land Registry; and Major-General M. N. MacLeod, previously Director- General of the Ordnance Survey.     

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.     

LOCAL ATTRACTIONS AND THEIR INFLUENCE ON THE DETERMINATION OF HEIGHTS ABOVE MEAN SEA LEVEL

Abstract

Preliminary Note.—The substance of this article was written in 1921 at the request of Lieut-Col. Wolff, who was then in charge of the Levelling Division of the Ordnance Survey and with whom the author collaborated in writing “The Second Geodetic Levelling of England and Wales, 1912–21” under the direction of Sir Charles Close. It was not intended for publication and was not again considered until 1928, when a discussion by correspondence was started by the Surveyor-General of Ceylon on the subject of hill circuits in levelling. In this discussion the survey authorities in Great Britain, Canada, India, and South Africa took part, but the main theme was the accumulation of error due to the large number of sightings necessary in hilly country and the question whether a common formula for such country and for flat country was justifiable. In his contribution Dr. van der Sterr made a brief allusion to the subject of the present paper and Dr. de Graaff Hunter went into details. His contribution and the following remarks therefore have some arguments in common.     

STANDARDIZING EQUIPMENT OF THE GOLD COAST SURVEY DEPARTMENT

Abstract

The following account of the standardizing equipment of the Gold Coast Survey Department has been written, at the request of the Editor of the Review, because this equipment includes a completely enclosed standard of length 300 feet long which is believed to be one of the very few enclosed standards of this length in any of the Crown Colonies.     

THE ORDNANCE SURVEY FOOT/METRE CONVERSION RATIO

Abstract

The Figure of the Earth used by the Ordnance Survey for its work in Great Britain is that given by Sir George Airy in the “Encyclopaedia of Astronomy” in an article on the Figure of the Earth. It is universally known as Airy's Figure.     

Maps for the Reluctant

Abstract

This paper describes the design and development of two trial 1:100 000 scale Ordnance Survey maps targeted specifically at the inexperienced and reluctant map users in the touring and holiday market. These are two maps which depart from the very high map specification designs normally offered by Ordnance Survey. The use of extensive consumer market research and the objective analysis of existing touring type maps on sale have enabled Ordnance Survey to publish two experimental maps, which will succeed or fail by consumer reaction alone.     

SURVEYS AND HISTORY

Abstract

Not long ago a very energetic and able soldier-surveyor said to me, “Why do people indulge in all this hero worship? Our forerunners in the Survey were not so remarkable”. Perhaps, on the few occasions when any of us do write Survey history, distance and loyalty add enchantment to the memories. But there is little harm in that. Besides some, at least, were great men. It is not perhaps of much value to our present work to read how Captain Drummond invented the limelight, in order to get his connexions across the Irish Sea. It does not help us much, although it is very interesting, to know how the Ordnance Survey stumbled on photozincography just at the same time as an Australian in Sydney. On the other hand it is of great importance to know just what standards Clarke did gather together for his great series of comparisons. It is of importance to know how the need arose for this scale or that, from the town plans to the I/M, for the same needs still exist. It is sadder but even more important to know how, entrusted with a magnificent field of action, the Survey gave up this item or that to the great inconvenience of the public. Survey history gives a yard-stick by which to assess the value, the authenticity and the precision of such measurement or topography as still underlies our work. It encourages us by showing what obstacles lcan be overcome, and it also teaches us to avoid the dangers, delays or mistakes we may, all unwittingly, repeat. The last are many indeed. Ordnance Survey history is full of warnings of that sort, for “the evil that men do lives after them; the good is oft interred with their bones”.     

LOCAL ERRORS IN RELATION TO ANALYTICAL METHODS OF AIR TRIANGULATION

Abstract

In view of the limitations of the use of plotting machines in air triangulation a detailed investigation of the practical possibilities of the analytical methods has become necessary, especially now that inexpensive means of reducing the labour of calculation is in course of realisation.

In analytical methods it is practically possible to correct the measured photographic coordinates for determinable errors. Also, the use of a reseau as developed by the Ordnance Survey facilitates the reduction of several distortions. It is however argued and demonstrated that some errors of a local character remain without effective checking.

A discussion of the nature of local errors shows that the number of points usually employed for relative setting is too small to be effective in disclosing them. An increase of the number of observed points is therefore suggested, and should be expected to improve the accuracy in the meanwhile.

An assessment of the value of doubling the number of minor control points and of the improvement resulting from the use of reseau is made from a statistical analysis of data kindly provided by the Ordnance Survey.

Comparison of 89 overlaps carrying one centimetre reseau and 100 overlaps without the reseau shows that the use of reseau reduced the root mean square error of evaluation of want of correspondence by 13 per cent., which just passes the 10 per cent. point of significance. The use of double minor control on the reseau overlaps gave an improvement which is about equal to that due to the use of the reseau. Doubling the number of minor control points is shown to increase the effective number of degrees of freedom from one to an average of four, which should reduce effectively the chances of large errors passing unnoticed through the stages of relative setting.

Work on the frequency of local errors of various sources is in hand, and will probably be published in later issues of the Review.     

Editorial

Abstract

This paper describes the conservation of the first edition of the six-inches-to-one-mile Ordnance Survey maps of Ireland. It outlines the general problem of the acidity of paper on which nineteenth-century Ordnance Survey maps are printed and the peculiar problems of conserving a hand-coloured presentation set. Each stage in the process is described up to the final encapsulation of the maps in Melinex polyester film.     

A knowledge based system for cartographic symbol design

Abstract

The work of the Ordnance Survey in Scotland has been rarely considered at a local level. Several bodies in Glasgow contributed to an extensive correspondence regarding the plan of the city and the appropriate scales of survey. This paper discusses the representation as an insight onto a wider perspective of the development of Ordnance Survey policy in the mid-Victorian era.     

A DIRECT METHOD OF TRANSFORMIG RECTANGULAR COORDINATES FROM THE CASSINI PROJECTION TO THE GAUSS CONFORMAL PROJECTION

Abstract

I. Introduction.-For some little time the Ordnance Survey was engaged upon the problem of transforming the rectangular coordinates of trigonometrical stations from the Cassini projection to the Gauss Conformal projection. The problem was complicated by the fact that the Cassini projection, as is well known, was applied to a number of meridians of origin, a different meridian being used for a county or a group of counties. It was proposed, however, to have only one meridian for the Gauss projection and to drop the county meridians completely. In both projections the northings were measured from the same parallel.     

A FIFTY-YEARS RETROSPECT

Abstract

The Ordnance Survey and the War.—I shall not inflict upon the readers of this Review any very long account of the work of the Ordnance Survey during the Great War. At that time the work of the Survey suffered from one necessary disadvantage: all the young men on its establishment, whether in the R.E. Companies or on the Civil Staff, left for active service. As a slight compensation for this inevitable dislocation all money difficulties in the preparation of maps for war disappeared.