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.     

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.     

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.     

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

1　ＩｎｔｒｏｄｕｃｔｉｏｎＡｇｅｏｇｒａｐｈｉｃｉｎｆｏｒｍａｔｉｏｎｓｙｓｔｅｍ (ＧＩＳ)ｉｓｕｓｅｄｔｏｃｏｌｌｅｃｔ,ｄｉｓｐｌａｙ ,ａｎａｌｙｓｅａｎｄｍａｎａｇｅｇｅｏｇｒａｐｈｉｃａｌｌｙｒｅｌａｔｅｄｉｎｆｏｒｍａｔｉｏｎ .Ｉｔｉｓａｎｉｍｐｏｒｔａｎｔｔｏｏｌｔｏｉｎｔｅ ｇｒａｔｅｓｐａｔｉａｌｄａｔａａｃｑｕｉｒｅｄａｔｄｉｆｆｅｒｅｎｔｓｃａｌｅｓ,ｔｉｍｅｓａｎｄｆｏｒｍａｔｓ.ＧＩＳｉｓａｍｅａｎｓｏｆ1 )ｅｘｃｈａｎｇｉｎｇｉｎｆｏｒｍａｔｉｏｎｂｅｔｗｅｅｎｃｏｕｎｔｒ…     

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—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–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 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.     

SETTING UP DIGITAL ELEVATION MODEL(DEM) ON THE BASIS OF SCANNED RASTER DATA FROM CONTOUR LINE SEPARATIONS

The application of Digital Elevation Model (DEM) is drawing more and more attention.Different ways to set up DEM are being tested in line with various local conditions.This paper describes the experiment of setting up DEM on the basis of scanned raster data from separations of contour lines after the pre-processing of the contour image and the running of a program on a microcomputer.The software is designed to simulate the intelligent activities of human experts in evaluating the point elevation for the DEM.     

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

1　ＩｎｔｒｏｄｕｃｔｉｏｎＷｉｔｈｔｈｅｒａｐｉｄｄｅｖｅｌｏｐｍｅｎｔｏｆａｅｒｉａｌａｎｄｓｐａｃｅｒｅｍｏｔｅｓｅｎｓｉｎｇｔｅｃｈｎｉｑｕｅ,ｔｈｅｄｉｇｉｔａｌｃａｍｅｒａｈａｓｂｅｅｎｅｘｐｌｏｒｅｄ ,ａｎｄｍａｐｐｉｎｇｅｘｐｅｒｉｍｅｎｔｓｗｉｔｈｔｈｉｓｋｉｎｄｏｆｄｉｇｉｔａｌｉｍａｇｅｓａｒｅｂｅｉｎｇｐｒｏｃｅｓｓｅｄａｓｔｈｅｒｅｇｕｌａｒｍｏｄｅｏｆａｒｅｏｐｈｏｔｏｇｒａｍｍｅｔｒｙ .Ｏｎｔｈｅｏｔｈｅｒｈａｎｄ ,ｔｈｅｔｅｃｈｎｉｑｕｅｏｆｉｎｔｅｇｒａｔｉｏｎｏ…     

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).     

DEVELOPING THE CARTOGRAPHIC SKILLS OF GEOGRAPHY STUDENTS (Organization of laboratory work in the “Cartography” course)

The authors describe the content and objectives of laboratory work in the general cartography course at Moscow University. The course is taken by all third-semester geography students, with laboratory work designed to develop basic skills in mapping and map use rather than supply professional cartographic training. A lab syllabus, designed as a model for similar courses throughout the USSR, permits comparison of Soviet emphases with those prevailing in North American universities. Considerable attention is devoted to development of evaluative skills (selection of suitable projections, methods of presentation, etc.) and recognition of basic sources of cartographic information. Translated from: Vestnik Moskovskogo Universiteta, geografiya, 1984, No. 5, pp. 43-48.     

全球定位系统(GPS)的最新进展(下)

3　动态 GPS定位自从利用 GPS载波相位观测的机载动态定位于 1 985年第一次得到证实之后 ,可靠的 GPS解支持航空摄影测量、遥感活动和地球物理测量的能力显著改进了。这些改进来源于若干因素的综合 :第一 ,运动 GPS接收机可以跟踪 8颗或更多颗卫星 ;第二 ,可以得到精密星历供后处理之用 ;第三 ,提出了一些算法 ,它们能以少量的相位和伪距观测量在运动中初置相位偏差。这些因素综合起来 ,产生了精确到厘米级的动态定位能力。这就是动态 GPS定位技术。它可以把距离延伸到约 1 0 0 km。采用 KARS( Kine-matic And Rapid Static)程序…     

全球定位系统(GPS)的最新进展(上)

首先分析了 GPS观测的主要误差源。其次 ,叙述了空基 (星载 ) GPS的科学应用 ,其中 TOPEX和 Micro L abe任务都是成功的范例。关于 GPS对于气象学的应用 (GPS/MET)方面 ,比较详细地介绍了地基 GPS/MET和空基(星载 ) GPS/MET的最新进展 ,二者处于 GPS的最新进展的前沿。     

ON THE EVALUATION OF DEFLECTIONS OF THE VERTICAL USING FFT TECHNIQUE

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｆａｓｔＦｏｕｒｉｅｒｔｒａｎｓｆｏｒｍ (ＦＦＴ)ｔｅｃｈｎｉｑｕｅｉｓａｖｅｒｙｐｏｗｅｒｆｕｌｔｏｏｌｆｏｒｔｈｅｅｆｆｉｃｉｅｎｔｅｖａｌｕａｔｉｏｎｏｆｇｒａｖｉｔｙｆｉｅｌｄｃｏｎｖｏｌｕｔｉｏｎｉｎｔｅｇｒａｌｓ.Ｔｈａｎｋｓｔｏｔｈｅｇｏｏｄｃｏｍｐｕｔａｔｉｏｎｅｆｆｉｃｉｅｎｃｙ ,ｔｈｅＦＦＴｔｅｃｈｎｉｑｕｅ ,ｉｎｔｈｅｍｉｄ＿1 980ｓ ,ｂｅｇａｎｔｏｆｉｎｄｗｉｄｅｓｐｒｅａｄｕｓｅｉｎｇｅｏｉｄｄｅｔｅｒｍｉｎａｔｉｏｎ ,ｗｈｅｎｃｏｍｐａｒ…     

THE CONSTRUCTION OF THE STANDARD BASELINE SITE IN CHANGYANG,BEIJING

The minutes of talks on co-operation forestablishing a standard baseline in China be-tween the Finnish Geodetic Institute and Na-tional Bureau of Surveying and Mapping ofChina was signed in Beijing on October 6,1983.After repeated comparisons and recon-naissance on geomorphology, geologic structure,subsoil water, precipitation, wind speed,atmospheric pressure, humidity, depth of