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.     

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 EAST AFRICAN ARC

Abstract

It was suggested some time ago in the Review (E.S.R., vol. ii, no. 9, p. 182) that observing procedure in a ruling triangulation should be made the subject of a discussion at the forthcoming Empire Survey Conference. I hope it will be. We shall perhaps learn why India finds thirty measures necessary, as no doubt they are necessary in India, whereas South Africa and Southern Rhodesia are able to secure much the same degree of accuracy from the same instrument with only eight; why Canada, again with the same instrument, prefers the golden mean of sixteen; why some of us still prefer the measurement of angles to directions vvhile others would insist entirely on the measurement of directions from a “close” R.O. It is only by pooling the experiences gained in diverse circumstances that we can avoid being overborne by our own successes or failures, encountered possibly in very exceptional circumstances which may not recur.     

THE EAST AFRICAN ARC: IV. BASE MEASUREMENT

Abstract

The gear used for the measurement of the Kate Base of the East African Arc was specially designed by McCaw in conjunction with Messrs. Cooke, Troughton, & Simms, as a result of considerable experience in the measurement of geodetic bases in Fiji, Sweden, and in various parts of Africa; it is now known by the trade name of the “Macca” Base Measurement Gear. It has since been used in Southern Rhodesia, Tanganyika, Mauritius, and South Africa, and if the central pool of instruments recommended at the recent Empire Surveyors Conference is approved, it seems likely that its beat will soon be still more extended. It must be about the only first model of a surveying instrument which has not occasioned widespread controversy and complaint, and for this desirable state of affairs it is not unreasonable to suppose that the rare co-operation between the practical surveyor and the instrument-maker in its design is responsible.     

TRAINING AFRICAN SURVEYORS IN UGANDA

Abstract

Under the Buganda Agreement, which was made in 1900 between the British Government and the Kabaka (King) of Buganda, approximately 9,000 square miles of the kingdom of Buganda were divided into numerous estates, which were allocated to the various reigning chiefs and people of importance at that time. The British Government agreed to survey these estates, most of which were one square mile in area; thus, the term “Mailo” as applied to the land owned by the Baganda, came into use. Since the original Mailo survey, which was completed in 1935, many of the estates have been subdivided. The land has been sold piecemeal, gifted and bequeathed, so that plots now exist which are even less than one acre in area and some in and near large townships are as small as half an acre. The task of the Survey Department is a gargantuan one and, in 1949, it was estimated that there were some 150,000 outstanding surveys.     

THE LAY-OUT OF THE EAST AFRICAN ARC

Abstract

The only essential difference between geodetic triangulation and any other of the fifteen “orders” of triangulation—which were once proposed, and happily rejected, at an International Conference—is that steps are taken to secure the high degree of accuracy necessary over the large areas to be covered. Some of the steps taken to secure increased accuracy may well be used to insure economy in secondary work, as for instance the use of fewer readings of a large instrument, or the use of luminous signals in conditions of poor visibility; while any surveyor may at any time have to connect his work to a geodetic triangulation, using much the same methods.     

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.     

INFRA-RED LINE-SCAN IMAGERY: AN EXAMPLE AND AN APPLICATION

The detection of drainage patterns in an area of the Forest of Dean, Gloucestershire, provides an example of the usefulness of infra-red line-scan imagery.     

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.     

TRIPLE RESECTION: AN EXAMPLE

Abstract

By triple resection is meant the simultaneous fixing of three field points by observations therefrom to two or more points of control. Of several cases one is considered here.     

PHOTOGRAMMETRIC DATA CAPTURE: AN INEXPENSIVE ALTERNATIVE

A case is made for the development of an inexpensive and portable data capturing unit which could be used with existing mirror stereoscopes and which could provide an accuracy sufficient for most digital map databases. The results of simulation experiments to test the accuracy of the system are presented.     

改进最大似然遥感影像分类方法——以SAR影像为例

针对常规最大似然分类算法中类别先验概率获取困难及遥感影像分类问题,提出了一种有效的改进最大似然遥感影像分类方法.该方法能使用类别样本的统计信息,实现类别先验概率的自动和最优提取,从而很好地解决了基于统计监督分类方法中无法直接获取类别先验概率的问题.以6景Radarsat-1 精细模式SAR影像数据为例进行的分类实验证明,该算法分类效果较好,针对单波段、单极化的SAR影像,其精度可望达到80%.     

KING GEORGE ISLAND GIS (KGIS) PROJECT OF WGGGI——A STATE OF THE ART

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DIGITAL GROUND MODELS: AN ACCOUNT OF RECENT RESEARCH

The article discusses a general classification system applicable to digital ground models (D.G.M.) as used in highway design. Examples of the various categories are given, together with details of some advantages and disadvantages. The place of the D.G.M. in the highway design system is described in conjunction with traditional methods. The relationship between accuracy, density and economy of D.G.M. systems is examined. Finally an experiment is described which investigates the accuracy of various D.G.M. systems; it is being conducted by the Transport and Road Research Laboratory.     

紧凑二叉树表示法──一种有效的图像表达技术

本文介绍了一种新的图像表达技术──紧凑二叉树表示法,给出了该技术的编码方法,讨论了基于紧凑二叉树表示的图像操作过程。通过与其它图像表达技术的比较和分析表明,紧凑二叉树表示具有较高的时空效率。