TEMPERATURE ERRORS IN PRECISE TRAVERSING

Abstract

It is assumed that a precise traverse would be used only where triangulation would be impracticable, that an absolute accuracy of I in 100,000 would be required, and that reasonable speed would be necessary.     

ERRORS IN DEPTH DETERMINATION CAUSED BY WAVES IN THROUGH-WATER PHOTOGRAMMETRY

The determination of depths in shallow water from aerial platforms will become increasingly important as exploitation of coastal resources intensifies. Until a theoretical study of the errors in depth which could be reasonably expected from two-media photogrammetry was made by Okamoto in 1982, there was little relevant literature apart from some isolated case studies. This paper examines the magnitude and distribution of errors in depth caused by the presence of waves on the water surface. The effects of random errors of observational measurement, in combination with waves, are assessed. A conclusion is reached that the traditional method of underwater depth calculation should be modified when the scale of the two media photography is greater than 1:4000.     

抗差岭估计的误差影响测度

当观测值受异常污染影响而不服从正态分布，且平差法方程出现病态时，采用抗差岭估计可得到参数的理想解。本文基于抗差岭估计理论，导出了抗差岭估计的误差影响函数，以及实用的抗差岭估计参数解差和参数解差函数，并结合实例作了多种的试算和比较，结果表明，抗差岭估计的误差影响函数对模型及参数解的理论分析具有重要意义，参数解差函数计算方便，几何意义明确。     

测距仪周期误差的显著性判别

本文对测距仪检定中判断仪器是否存在周期误差的三种方法——图示法、统计检验法、计算法作了系统介绍,并采用二元线性回归方法导出了计算法的判别公式。     

SIMPLE RESECTION

Abstract

The figure which follows shows the geometrical solution of Simple Resection by Cassini in 1669, two years before the Collins solution. It is clearly the geometrical illustration of the Delambre (1786) solution; for d_b = b cosec β, d_c = c cosec γ and the angle QAR is known, being BAC + β + γ ? 180°. Hence the Delambre solution-that in most common use to-day—reduces to a triangle in which two sides and the contained angle are given, as has been mentioned elsewhere.     

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.     

THE ERRORS IN A RADIAL LINE PLOT OF AIR PHOTOGRAPHS

Abstract

Lieut.-Col. Browne's interesting method of combii1ing radial line plots (“The Application of Transformation Factors to the Adjustment of Air Photographs”, E.S.R., x, 73, 119-130) depends for its success on the basic accuracy of the radial line plots of the individual air photo strips. It therefore poses the very interesting question: What accuracy can we expect in a graphical radial line plot?     

GNSS形变监测中系统误差的时空相关性研究

通过大量实测数据分析了系统误差的时空变化规律,论证了具有时空相关性的双差观测值系统误差残差的存在,实现了观测值的滤波及求差,提高了分离微小形变量的精度。     

ERRORS IN THE INDICATION OF GEOSYSTEMS FROM REMOTE SENSING IMAGERY

After a general discussion of principles of remote sensing indication and image recognition theory, the particular errors in this process are analyzed individually: errors in data recording; errors in automated image analysis; errors in interpretation of the content of geosystems; errors in the selection of interpretation keys; and finally errors in generalization and the extrapolation of results. The total error in geosystem indication from remote sensing imagery can be determined by an analysis of these particular errors. Translated by Edward Torrey, Alexandria, VA 22308 from: Geografiya i prirodnyye resursy, 1988, No. 4, pp. 98-107.     

A RESECTION METHOD

Abstract

This is a variation of the well-known device of successive approximations. It was first used by the writer about 15 years ago on a Seismic (Geophysical) Survey when resections were continually employed to locate Shot Points and Geophonestations set on arcs of 10 to 15 miles radius. Speed was an important factor, and the normal text book methods of resection were very tedious. As far as is known the method is original. It is now used by many surveyors, and the writer trusts it will be of use to others. The method is easy to remember as it has no set formula and does not involve any elaborate geometrical construction.     

一种特殊的后方交会法

本文对特殊的后方交会法的布点、观测、解算作了一般性的介绍，重点讨论了放样允许误差区域的确定．     

COMPUTING A RESECTION

Abstract

The method described below may be novel to some readers, and in certain circumstances may have the advantage of speed in comparison with more usual methods of computation.     

测量误差与不确定度

主要介绍了误差与不确定度概念的区别和联系，并通过实例对不确定度各分量进行分析、合成和计算，初步探讨了不确定度的评定与表示步骤及方法。     

TWO PROBLEMS OF RESECTION

Abstract

That admirable annual, The Surveyor (Ceylon), was generously forwarded to us some months ago. In this issue, vol. 2, no. 4, p. 93, there is given the solution of a question on resection in an examination paper. Since the solution appears rather laboured and the problem is interesting in itself and by no means valueless, it seems not out of place to attempt a simpler and more obvious answer.     

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.     

A MACHINE METHOD OF RESECTION

Abstract

With the modern calculating machine in easy reach of every computer, the problem of determining the position of an occupied point from which direction observations have been made to three or more known points has become quite simple. The method outlined below is quite elegant in form and exceedingly simple on the machine. Let A, B, C be the three points whose co-ordinates (X₁Y₁), (X₂Y₂), (X₃Y₃) are known, and let (XY) be the co-ordinates of the point P which we wish to fix.     

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.