LONG LINES ON THE EARTH

Abstract

The Arc of the Geodesic.—In the first part of this paper a method was given for computing the azimuth of a geodesic. The method gives the convergence of the geodesic correctly up to the second power of e the eccentricity. The formula (9), however, also depends on the assumption that σ, the arc-length of the geodesic, can be obtained with sufficient accuracy from the Supplemental Dalby Theorem, that is to say, by a purely spherical computation. It is, therefore, needful to show that this supposition is justifiable; a means must in fact be indicated for verifying the assumption.     

LONG LINES ON THE EARTH : VARIOUS FORMULAE

Abstract

The use of radar has already begun to revolutionise the science of surveying. It requires the computation of lines on the earth between a hundred and a thousand miles long for the fixation of topographic control.     

LONG LINES ON THE EARTH: VARIOUS FORMULAE

Abstract

Extensions were given for all these formulae, so that precise results may now be obtained even for lines of 500 miles in latitudes above 45°. The present instalment gives the extension of the Clarke approximate (sic) formulae to lines of 500miles, with a practical example and general conclusions: the great advantage of the method is that 8-figuretables sufficeto give rigorous results.     

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.     

NOTES ON THE BASE LINES OF THE CEYLON TRIANGULATION

Abstract

The triangulation of Ceylon depends for its scale upon two bases, each about 5½ miles long, situated at Negombo on the West Coast (latitude 7° 10′) and at Batticaloa on the East Coast (latitude 7° 40′). Both bases are in low, flat country; brick towers up to 70 feet high had to be built over the terminals to enable observations to be taken to surrounding points. These lines have recently been re-measured.     

A NOTE ON THE CALCULATION OF POSITION LINES

Abstract

Since the computation of a set of star observations generally takes far longer than the actual observing, the method used in computing the results should be carefully chosen in those cases where a choice exists. The calculation of Position Lines is such a case.     

POINT TO POINT COMPUTATION OF GEOGRAPHICAL COORDINATES OF LONG LINES

Abstract

The computation of geographical coordinates in a geodetic triangulation is usually carried out using Puissant's method, in which the assumption is made the sphere radius ν (the radius of curvature of the spheroid perpendicular to the meridian) not only touches the spheroid along the whole small circle of latitude ?,but also, since ρ (the radius of curvature in meridian) is very nearly equal to ν it makes such close contact with the spheroid that the lengths of sides and angles of a geodetic triangle may be considered identical on both sphere and spheroid.     

TM图像的大地校正及其镶嵌方法研究

大地校正和数字图像镶嵌是应用遥感图像进行资源环境监测工作的基础,其精度的高低将对后续工作产生直接影响。基于经过系统校正的TM图像内部几何精度高的前提,本文提出一种快速实用的大地校正及图像镶嵌方法,该方法避免了传统方法在应用控制点建立拟合方程时耗时长的缺点,保证了TM镶嵌图像的几何精度.     

AZIMUTH AND DISTANCE CORRECTIONS FOR THE GEODETIC LINES ON THE LAMBERT CONFORMAL PROJECTION

Abstract

The oblique or general case of the gnomonic projection receives little serious attention in most text books on map projections and in the works which do include the theory it is unfortunately developed with unnecessary complexity. In consequence it is much less widely understood than are the special cases represented by the polar and equatorial forms. Yet the oblique form provides a gratieule which has proved incomparably more useful than either of the two Inore obvious and popular special cases. Thus, oblique cases have provided the graticules for the series of gnomonic charts of the oceans published by the Hydrographic Department of the Admiralty; the G.S.G.S. Consol Plotting Charts and the Gnomonic Fixing Chart (prepared specially for use with long range radio aids to navigation) are all oblique gnomonic graticules as are the special purpose charts for position fixing from radio bearings published by the Admiralty. In addition, all large scale port plans included in the range of Admiralty charts are drawn on a modified gnomonic. It is only in connection with the production of facets for “near globes” that one can point to the use of the polar and equatorial cases of the gnomonic and even here the greater number of facets are produced as oblique cases.     

极移对地面重力及大地水准面的影响

地球自转轴的变动必然会导致地面重力值及大地水准面的变动。本文导出了这些变动的简便计算公式。计算结果表明,极移引起的地面重力变化最大达15μgal;大地水准面高的变化最大达5cm;垂线偏差的变化最大达0.003。这些量对目前及将来高精度大地测量产生的影响是不可忽视的。     

EXPERIMENTS ON THE GROUP GENERALIZATIONG OF CONTOUR LINES FOR TOPOGRAPHIC MAPS

ABSTRACT

This paper analyzes the advantages and disadvantages of two technical lines for automatic group generalization of contour lines. The author suggests that it is possible to get faster and better generalization results if we simulate the intelligence of human experts in program designing, retrieve geomorphological structural information using the input data of 2-D contour lines and derive and output the generalized 2-D results directly.     

EXPERIMENTS ON THE GROUP GENERALIZATIONG OF CONTOUR LINES FOR TOPOGRAPHIC MAPS

This paper analyzes the advantages and disadvantages of two techni-cal lines for automatic group generalization of contour lines.The author suggeststhat it is possible to get faster and better generalization results if we simulate theintelligence of human experts in program designing,retrieve geomorphologicalstructural information using the input data of 2-D contour lines and derive andoutput the generalied 2-D results directly.     

NOTES ON WATER LINES ON ADMIRALTY CHARTS

Abstract

It is understood that there is sometimes a little confusion as to the high and low water lines which are shown on British Admiralty charts; your readers may be interested to know the Admiralty practice.     

中国东部地区地壳垂直运动规律及其机制研究

本文４根据我国东部地区３７５６个重复水准点资料,提出了与我国东部地质构造相结合的新的数据处理思想,分别绘制了我国东部地区陆地与地壳垂直运动速率等值线圈。     

三维激光点云扫描线曲率压缩算法研究

提出了一种基于扫描曲线上各散乱点的曲率大小进行压缩的方法,实现了以曲线上各点的曲率大小为标准对扫描线数据进行精简压缩,试验数据取得了较好的压缩效果.     

THE COLOURS QUESTION: A BAFFLING FRONTIER PROBLEM

Abstract

“Checquy,undy; vert, azure, gules, etc., ad lib.; a medley of features couchant in congruence; motto: Verity, Clarity, Sufficiency.” Arms worthily won (and unaccountably secreted) by the Worshipful Company of Map-makers. … Their craft like many another has been swept into the headlong surge of science and the applied arts, and her crew might almost be forgiven if they conspired to meet the menace of voces populi with shrugged shoulders and plugged ears, and eyes turned astern to the pleasant bay where their forefathers rode at anchor and plied brush and crowquill. Yet they, too, had their problems and perplexities, those early craftsmen, and one at least has withstood the solvent stress of science and stands to-day where it stood when a man first stumbled upon it.     

关于连接两圆曲线的缓和曲线任意点坐标计算方法

本文主要阐述连接两圆曲线的缓和曲线任意点坐标计算方法及实例计算。