EVALUATION OF THE COEFFICIENT OF TERRESTRIAL REFRACTION

Abstract

In two previous articles (E.S.R., vol. iv, nos. 23 and 25) it was shown that, at the time of maximum diurnal temperature in the tropics, a definite relationship exists in the lower layers of the atmosphere between the magnitude of the coefficient of terrestrial refraction at a point and the height of that point above plain level, provided the weather is fine and clear. In fact the coefficient K increases with the height h, within certain limits which are probably defined by the condensation layer.     

THE ADJUSTMENT OF TRIGONOMETRICAL LEVELS AND THE EVALUATION OF THE COEFFICIENT OF TERRESTRIAL REFRACTION

Abstract

This paper is written primarily with the object of ascertaining how other Colonies and Dominions deal. with the adjustment of their trigonometricallevels; further, since the greater part of Nigeria is now covered by a framework of levels of primary accuracy it is of interest to examine the results. Moreover, the evaluation of the coefficient of refraction, and from it the temperature lapse-rate, is of some importance in view of the recent publication of the War Office Aneroid Tables. These tables are based on a standard lapse-rate of temperature.     

TRIGONOMETRICAL HEIGHTS AND THE COEFFICIENT OF TERRESTRIAL REFRACTION

Abstract

Mr. A. J. Morley has contributed a series of articles in the Review (E.S.R., iv, 23, 16; iv, 25, 136 and vi, 40, 76) on the adjustment of trigonometrical levels and the evaluation of the coefficient of terrestrial refraction with a view to ascertaining how other Colonies and Dominions deal with these problems. This object is very commendable as several problems concerning both the observational and theoretical sides arise in height determinations, regarding which there is not much guidance in the usual treatises on the subject.     

THE VARIATION OF THE ATMOSPHERIC COEFFICIENT OF REFRACTION WITH THE NATURE OF THE SOURCE OF LIGHT

Abstract

In working out vertical heights on the Akuse-Kete Krachi chain of triangulation in the Gold Coast a fairly considerable difference was found between values of the coefficient of refraction obtained from observations taken during the day and those taken at night, the mean values being 0.069 for daylight observations to heliographs and 0.087 for night observations to lamps. This difference no doubt is due mainly to the condition of the atmosphere during the day differing from its condition during the night rather than to any effect due to different sources of light. A new chain has recently been observed in Western Ashanti, and the index of refraction for the daylight observations again gave a lower value than that obtained from the night observations, the figures being 0.073 and 0.099 respectively. For the night work three different sources of light were used, hurricane lamps for short lines, Tilley vapour-pressure lamps for lines of intermediate length, and McCaw acetylene signalling lamps by Watts for long lines. It occurred, therefore, to the writer to examine the results to see if the mean values of the index of refraction showed any variations for the different light sources, since it seemed reasonable to suppose that the constitution of the light emitted from each source would be different and hence that the coefficient of refraction might vary.     

中性大气折射的映射函数

在球对称大气模型下，我们导出了与余误差函数形式相联系的中性大气折射改正的母函数，并进一步讨论了它的几种数学展开形式。由此方法建立的映射函数可以对各类大气模型直接进行参数拟合。     

FURTHER DEVELOPMENTS IN THE PHOTO-RADIATION METHOD OF TERRESTRIAL PHOTOGRAMMETRY

The photo-radiation method of terrestrial photogrammetry was introduced in 1981 as an appropriate means of rapidly surveying large areas of open ground, primarily beaches. Since that time, several variations on the standard method have been tested. These have arisen from attempting to solve problems associated with particular situations. For instance, the use of the waterline as a means of contouring developed from a problem where a dangerous river bank was inaccessible for traditional survey observations. Another application concerned laboratory testing where photogrammetry is particularly attractive for measurement due to the coverage which is possible, together with the advantage that permanent records remain on film for later re-analysis. Both these variations in the photo-radiation method are described, together with an indication of the circumstances under which they have been successfully applied.     

ELIMINATION OF ERRORS OF LATITUDE AND REFRACTION IN THE PAIRING OF AZIMUTH OBSERVATIONS

Abstract

In a previous Article (Empire Survey Review, ii, II) I described a simple graphical method for the elimination of latitude error in observations for azimuth. It was pointed out that the ideal method of adjustment of azimuths would be a simultaneous elimination of both latitude and refraction errors and, with that in view, a purely theoretical method of such an adjustment was demonstrated in the last paragraph of the article. It has now occurred to me that a fairly simple mathematical solution is possible.     

CORRECTION OF PLANE-TABLE HEIGHTS FOR CURVATURE OF THE EARTH AND ATMOSPHERIC REFRACTION

Abstract

Most text-books on surveying limit their discussion of the correction of vertical angles for curvature of the earth and atmospheric refraction to the correction of angles taken with a theodolite during triangulation and omit any reference to those taken with a clinometer. This is rather illogical, as in well-observed triangulation, with all vertical angles measured in both directions, no correction for these effects is necessary, whilst in plane-tabling on small scales where sketching at considerable distances is frequently employed the application of corrections for these effects is essential.     

A NOVEL METHOD OF MEASURING THE COEFFICIENT OF THERMAL EXPANSION OF INVAR

Abstract

In a letter published in a recent issue of Nature, Prof. L. F. Bates and Mr J. C. Wilson, of University College, Nottingham, have described a new and novel method of determining the coefficient of thermal expansion of invar. Although this method is hardly likely to be applied to the measurement of the coefficient of expansion of long invar tapes, such as are used by surveyors, yet it is so novel and ingenious in itself that a short reference to it may not be out of place in this Review. One extremely interesting thing about it is that no measurements of a length, or of changes of length, are involved.     

空中测量地面平均重力异常的频域分析

本文首先给出了地面点重力异常代表误差的频域算式，进而将频域概念推广到空中重力异常的代表误差，推导出用空中一点重力异常代表地面一定块形平均重力异常的代表误差频域算式，据此可以讨论在空中测定地面平均重力异常的最佳高度。     

空间数据精度的检查和评价方法研究

从GIS空间数据精度出发,论述了空间数据误差的影响因素,提出空间数据精度的评价方法和确定空间数据精度实际检查过程中应注意的问题,并以实际工作成果说明本文提出的空间数据精度检查及评价的效果。     

尺度参数的Lp估计与精度评定

根据定位参数与尺度参数的联合Ｍ估计,导出了尺度参数的Ｌｐ估计;当ｐ＝２时,与最小二乘估计一致,观测数据服从正态分布时,为最优无偏估计;由于尺度参数Ｌｐ估计的影响函数为无界函数,估计不具抗差性,但把残差Ｗｉｎｓｏｒ化,作者得到了尺度参数的抗差Ｌｐ估计;依据定位参数的协方差阵,可进行Ｌｐ估计的精度评定。这些结果对于Ｌｐ估计的研究和应用具有一定的参考价值。     

杠杆点评估及设计空间抗差

本分析了杠杆点的几何含义和统计特征,从杠杆点的保差性,矩阵的摄动和参数估值可靠性的观点出发讨论了杠杆点的不利和有利的两个方面,提出了一个全面的设计空间抗差方案。     

遥感技术在下庄地区地热资源开发中的应用研究

通过遥感、物探和地质钻探等技术对邯郸市下庄地区的地热资源进行了识别、印证和应用方案研究,探索了遥感技术在小区域应用的方法和途径,揭示了遥感技术的广阔应用前景。把遥感研究成果应用于可实施的工程建设方案,是遥感技术在小区域资源调查研究和开发应用上的一个成功范例.     

DISTANCES AND REFRACTION ON OR NEAR THE APPARENT HORIZON

Abstract

An observer looking seawards views the horizon along a curvilinear path which is tangent to the surface of the sea. The distance to the tangent point depends on the height of his eye. The angle of depression of the ray at the observer's standpoint is known as “the dip of the visible sea horizon”.     

层次分析法在生态环境综合评价应用中的优化

层次分析法（Analytical Hierarchy Process,AHP）,是一种常用的系统分析与决策方法,但在应用于青藏高原区域生态环境综合评价时,由于因素的权重值只能为正数,影响了表达效果。为此,本文对其进行了优化,改进了构造判断矩阵时的赋值方法,在评价过程中引入了负数。实验证明,优化后的方法能准确地评价青藏高原的生态环境。     

利用TM资料评估森林风灾损失

本文简要地介绍了利用TM资料进行森林风灾损失调查的意义和利用计算机处理提取风灾信息的方法；列举了长白山林区风灾面积、林木蓄积量和分布范围的遥感调查结果；评述了应用遥感方法进行森林风灾调查的优点。     

工程方案的GIS系统评价模型应用研究

本文对工程设计中工程方案比选的GIS系统分析进行了探讨研究,着重阐述了工程方案的GIS评价方法和评价模型,并以南水北调西线工程雅砻江调水渠线方案的系统评价为例作了试验。