共查询到20条相似文献，搜索用时 15 毫秒
1.
《测量评论》2013,45(81):118-128
AbstractSurveying tapes of steel are much more satisfactory mechanically than those of invar, and are less subject to secular changes of length, but the magnitude of their coefficient of thermal expansion demands a closer knowledge of their temperature than can be obtained with ordinary thermometers suspended near the tapes. The measurement of steel tapes in terms of their electrical resistance has therefore been investigated. The history of this work is traced. The use of resistance methods has proved satisfactory in the field, and under Laboratory conditions at the N.P.L. the accuracy of 1 part in 2 millions in the measurement of the lengths of 24-metre and 100-foot tapes of steel is attained. Such steel tapes appear to have remained stable on the average within about 2 parts in a million in 25 years. 相似文献
2.
《测量评论》2013,45(89):110-115
AbstractThe difficulty of determining the true temperature of a surveying tape when in use in the field, particularly in bright sunlight, is discussed. A simple form of resistance thermometer made of invar tape is described and the results of comparisons made between the temperatures determined by this thermometer and those recorded by mercury thermometers under various conditions in the field are summarized. Under cloudy conditions, mercury thermometers, with bulbs screened or unscreened and as normally used by surveyors, gave results at all temperatures between O°C. and 25°0. within ±1°C. of the temperature indicated by the resistance thermometer. But in bright sunshine in Southern England, a mercury thermometer was found to record temperatures as much as 4°C. lower than that indicated by the resistance thermometer.It is not practicable in the field to use the invar measuring tape itself as a resistance thermometer; the Use of a resistance thermometer made of invar tape and situated in the neighbourhood of the measuring tape is therefore recommended for determining the mean temperature of a measuring tape when working in bright sunlight. 相似文献
3.
标尺误差是精密水准测量的一项重要误差来源。其中由于温度变化而引起因瓦带的长度变化,是使用因瓦标尺带来的误差之一。国内外有关文献曾对此进行过深入的研究。我国过去在精密水准测量时,未测定所用因瓦标尺的综合膨胀系数,故在一等水准网平差中未对观测高差加标尺温度改正。本文主要针对将要开始的精密水准复测,讨论标尺的温度改正问题和我们的试验结果。 相似文献
4.
《测量评论》2013,45(40):76-93
AbstractIn 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. 相似文献
5.
AbstractFor the sake of the junior reader we may repeat an old and simple investigation. Let us suppose that the paper on which a map is printed undergoes a regular expansion p in one direction, say the X direction, and another regular expansion q in the Y direction, perpendicular to the former; it is required to know the effect of these expansions on the area of any parcel on the map. Note that, so far as the mathematics are affected, X and Y are not necessarily parallel to the margins of the sheet; we shall take them here as axes of any rectangular coordinate system. The symbols p and q are regarded as ratios, so that 100p and 100p represent the percentage expansions; if the paper contracts instead of expanding, no more is necessary than to change the sign. 相似文献
6.
AbstractThe constant K in equation (12) represents distance expended through time lags in the instrument itself, and, although the value of K can be calculated from electrical data, this would not be very satisfactory and it would be better to determine it directly by means of observations over a line of known length. In addition, the point from which K would be reckoned is not a convenient one for actual field measurements. Instead of this, it is more convenient to choose an index mark on the instrument itself and referall measurements to this and thence to the mark over which the instrument is set up. 相似文献
7.
《测量评论》2013,45(25):136-140
AbstractIn a previous article on this subject (Empire Survey Review, January 1937) the writer sought to show that for trigonometrical observations of vertical angles made near noon in the Tropics the coefficient of refraction depends chiefly on height above ground level in the case of stations sited within a few hundred feet above the general level of the ground surface. Indeed, the computed values of the coefficient K show a definite and appreciable increase with “h”, the height of the observing station above ground level; it is usually assumed that K decreases with increase in height above the Mean-Sea-Level surface. From analysis of the results obtained by varying h but holding the heights above Mean Sea Level fixed the writer came to the conclusion that the variations in K could only be due to abnormal values of dt/dh and d2t/dh2, “t” denoting the air temperature. Now it is generally recognized by meteorologists that abnormal lapse-rates of temperature do frequently occur in the lower air layers in the Tropics; but up to the present time no temperature soundings in Nigeria are available. Recently, however, the writer came across the results of the aerological soundings made by an expedition in East Africa during the year 1908. The results of many of the soundings were of no use for the purpose of this paper; many of the observations were not taken at or near noon, and in others counterlapses of temperature in the lower layers indicated that conditions were not normal. A set of observations taken at Mombasa between 10 and 11 a.m. were eventually chosen as offering an example of what might reasonably occur in the lower layers of the atmosphere. 相似文献
8.
《测量评论》2013,45(87):31-36
AbstractThis paper continues the discussion started in an article of the same title (E.S.R., ×, 78, :353-66), on which a further letter was written in October, 1952. The amount of computation required originally was very considerable, and it was obviously impossible to publish it all. The recent letter was necessary to answer the suggestion that the agreement between errors put in and corrections obtained from the L.S. solution was not very close. It seemed sufficient to give the list of errors and corrections, leaving readers to judge for themselves. The correlation coefficient from the two sets of figures was 0.78, which looked quiteg90d. Unfortunately, it was not realized before that corrections from a L.S. solution cannot, legitimately, be compared with errors put in on directions unless a station correction is first applied to the errors to make the sum of the errors at each station equal to zero. This is one of the points about the direction method of adjustment which is not very easy to understand. 相似文献
9.
《测量评论》2013,45(85):319-325
AbstractIn a recent issue of this Review, an example is given of the conformal transformation of a network of triangulation using Newton's interpolation formula with divided differences. While the application of the method appears to be new, attention should be drawn to the fact that Kruger employed Lagrange's interpolation formula in a discussion and extension of the Schols method in a paper which was published in the Zeitschrift für Vermessungswesen in 1896. A reference to this paper was given at the end of the paper, “Adjustment of the Secondary Triangulation of South Africa”, published in a previous issue of the E.S.R. (iv, 30, 480). 相似文献
10.
《测量评论》2013,45(19):258-266
AbstractThe following account of the standardizing equipment of the Gold Coast Survey Department has been written, at the request of the Editor of the Review, because this equipment includes a completely enclosed standard of length 300 feet long which is believed to be one of the very few enclosed standards of this length in any of the Crown Colonies. 相似文献
11.
In satellite data analysis, one big advantage of analytical orbit integration, which cannot be overestimated, is missed in
the numerical integration approach: spectral analysis or the lumped coefficient concept may be used not only to design efficient
algorithms but overall for much better insight into the force-field determination problem. The lumped coefficient concept,
considered from a practical point of view, consists of the separation of the observation equation matrix A=BT into the product of two matrices. The matrix T is a very sparse matrix separating into small block-diagonal matrices connecting the harmonic coefficients with the lumped
coefficients. The lumped coefficients are nothing other than the amplitudes of trigonometric functions depending on three
angular orbital variables; therefore, the matrix N=B
T
B will become for a sufficient length of a data set a diagonal dominant matrix, in the case of an unlimited data string length
a strictly diagonal one. Using an analytical solution of high order, the non-linear observation equations for low–low SST range data can be transformed into a form to allow the application of the lumped concept.
They are presented here for a second-order solution together with an outline of how to proceed with data analysis in the spectral
domain in such a case. The dynamic model presented here provides not only a practical algorithm for the parameter determination
but also a simple method for an investigation of some fundamental questions, such as the determination of the range of the
subset of geopotential coefficients which can be properly determined by means of SST techniques or the definition of an optimal
orbital configuration for particular SST missions. Numerical results have already been obtained and will be published elsewhere.
Received: 15 January 1999 / Accepted: 30 November 1999 相似文献
12.
《测量评论》2013,45(36):358-363
AbstractFew, most certainly, will dispute the value of Mr Black's paper describing a method of “Systematic Relaxation”, which appeared in a previous number of this Review. At the same time, however, it seems to the writer to be only fair to readers to point out that the application of the method to triangulation adjustment is really a treatment, from a slightly different aspect, of methods that have long been established. 相似文献
13.
《测量评论》2013,45(56):53-68
AbstractThis extremely simple and elegant method of computing geographical co-ordinates, given the initial azimuth and length of line from the standpoint, was published by Col. A. R. Clarke in 1880. There is no other known method giving the same degree of accuracy with the use of only three tabulated spheroidal factors. Clarke himself regarded this as an approximate formula (vide his remark in section 5, p. 109, “Geodesy”); but as this article demonstrates, it is capable of a high degree of precision in all occupied lati tudes when certain corrections are applied to the various terms. These corrections are comparatively easy to compute, require no further spheroidal factors, and some of them may be tabulated directly once and for all. 相似文献
14.
《测量评论》2013,45(100):265-269
AbstractIn the E.S.R. January and April numbers of 1955, Vol. xiii, Nos. 95 and 96, Mr. Hsuan-Loh Su described the “Adjustment of a Level Net by Successive Approximations and by Electrical Analogy”. It does not seem to be as generally known as it should be that the rigid least square solution can be greatly simplified by utilizing the electrical analogy and solving by Kirchhoff's method. The method as detailed below has been in use for over 40 years. 相似文献
15.
《测量评论》2013,45(91):231-232
AbstractThe correction to observed vertical angles for curvature and refraction can be found by adding a log factor to the log distance, which gives the log of the correction in seconds. This factor is 8·144 for metres and 7·628 for feet. The examples will make this clear. For machine computation, the correction in seconds can be obtained by multiplying the length in metres by 0.0139 or the length in feet by 0·00425. Alternatively, this can be done on the slide. rule by dividing the distance in metres by 72 or in feet by 235. The mean coefficient of refraction is taken as 0·07. 相似文献
16.
《测量评论》2013,45(93):311-316
AbstractThe advantages of subtense measurements with a horizontal base are well known, but this method has not yet gained much popularity witH the ordinary surveyor and an acknowledgment of, its usefulness in cadastral and engineering surveys has not yet found a proper place. Everyone knows the difficulties of direct chaining in hilly and rough country or in industrial and mining districts where numerous obstructions are usually encountered and where reliable accuracy throughout the area under survey would be difficult to maintain. Adoption of the subtense bar in such circumstances is the best answer to the problem, and the establishment of control points by this method assures economy and reliability. The subtense bar is easy and direct in use and the precision of the results obtained are comparable with precise chaining. The use of an invar bar or a steel tubular bar is essential in precise traversing with an accuracy of 1/10,000 or greater, but for ordinary control. traverses with an accuracy up to 1/5,000 the wooden bar may be sufficient. 相似文献
17.
《测量评论》2013,45(84):268-274
AbstractIn 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. 相似文献
18.
《测量评论》2013,45(62):300-311
AbstractChesterton did not, of course, intend this gibe to be taken literally. But the more we consider what he would doubtless have called the “Higher Geodetics”, the more we must conclude that there is some literal justification for it. Not only are straight lines straight. A sufficiently short part of a curved line may also be considered straight, provided that it is continuous (i.e. does not contain a sudden break or sharp corner), and provided we are not concerned with a measure of its curvature. Similarly a square mile or so on the curved surface of the conventionally spheroidal earth is to all intents and purposes flat. We shall achieve a considerable simplification, without any approximation, in the treatment of the present subject by getting back to these fundamental glimpses of the obvious, whether the formalists and conformalists accept them or not. 相似文献
19.
《测量评论》2013,45(43):270-271
AbstractIf it be assumed that the linear measurements of traversing are alone afflicted with error, the method of distribution of error demands consideration. In the present paper the notation of Wright and Hayford will be followed (“Adjustment of Observations”, 1906 edn., p. 156). 相似文献
20.
《测量评论》2013,45(78):353-366
AbstractIT has been assumed in the past that because angles for triangulation are usually observed by the direction method, therefore it must be more correct theoretically to perform the least-square adjustments by directions rather than by angles. It is fairly obvious that an adjustment of the same figure by directions will not give the same result as an adjustment by angles: the unknowns in each case are different and the number of directions is usually about 25 per cent. greater than the number of angles for the same figure. Strictly, the least square method is only applicable to observations from which all systematic errors have been eliminated, and in which the remaining errors are truly accidental. It is generally safe to assume that most survey errOlS consist of a random and a systematic part. Rarely, if ever, is it possible to state that all systematic error has been eliminated, strive how we may to take all precautions against it. 相似文献