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1.
《测量评论》2013,45(10):238-244
AbstractIn Trinidad the magnetic needle is used on all secondary surveys. The term “compass surveys” was given, unfortunately, to these secondary surveys in order to distinguish them from surveys carried out in open country in the ordinary manner with the theodolite oriented by means of solar observations or by bearings obtained direct from the trigonometrical framework. 相似文献
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《测量评论》2013,45(78):338-348
AbstractRadar can be applied to surveying for precise measuren1ent of long lines, and as a navigational aid and position-fixing device for an aircraft performing a photographic survey. Trials of the radar method have recently been carried out in Australia using a modified “Shoran” equipment. The results of a large number of radar measurements of six distances, varying from 160 to 310 miles in length, indicate that an accuracy of 7 parts in 105 can be achieved. Equipment errors constitute the immediate limit to accuracy, but reasonable modifications would yield a figure of 2 parts in 105. Radar measurements can be completed in a fraction of the time required by normal ground survey methods, since a measurement of upwards of a hundred miles is made in a single step.As an aid to photographic surveying a straight-line track indicator actuated by data from the “Shoran” equipment has been designed and flight tested. Its performance enabled a pilot taking aerial photographs to keep the aircraft to within an average departure of less than 0.02 mile from any desired straight-line flight path. 相似文献
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《测量评论》2013,45(50):158-160
AbstractApart from “stickiness” of the suspension and looseness of the sights, prismatic compasses are subject to three internal sources of error:- <list list-type="roman-lower"> <list-item>Collimation error. This may be caused by <list list-type="alpha-lower"> <list-item>magnetic axis not being parallel to the zero line of the graduated circle;</list-item> <list-item>line of sight not passing through the axis of rotation.</list-item> </list> It is unnecessary to aftempt to distinguish between the above faults, which introduce constant errors into the compass readings.</list-item> <list-item>Eccentricity error. This is caused by the axis of rotation failing to pass through the centre of the graduated circle. This introduces an error into the compass readings of E sin θ cosec I°/R where E is the eccentricity, R the radius of the graduated circle and θ the angle between the line of sight and the line joining the centre of the circle to the axis of rotation. Eccentricity error is completely eliminated by observing both forward and back bearings, but this is not always practicable.</list-item> <list-item>Irregular division of the graduated circle. This error is negligible in any modern compass.</list-item> </list> 相似文献
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《测量评论》2013,45(80):60-65
AbstractThe 200th anniversary of the publication by Murdoch Mackenzie (Senior) in May 1750 of his “Orcades, or a Geographic and Hydrographic Survey of the Orkney and Lewis Islands, in 8 maps”, is an opportune moment for a brief résumé of the contribution made by Mackenzie and his successors in the field of nautical surveying. The appearance of this work ushered in a new era in marine survey, for it was the first charting carried out in this country based on a rigid triangulation framework. The importance of this fact can further be appreciated when it is remembered that a contemporary topographic map like General Roys' famous “Map of the Highlands” begun in 1747 was little more than an elaborate compass sketch; thus under Mackenzie's influence, marine surveying at this period was ahead of its topographic counterpart. 相似文献
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ABSTRACTIntersections are the critical parts where different traffic flows converge and change directions, forming “bottlenecks” and “clog points” in urban traffic. Intersection travel time is an important parameter for public route planning, traffic management, and engineering optimization. Based on low-frequency spatial-temporal Global Positioning System (GPS) trace data, this article presents a novel method for estimating intersection travel time. The proposed method first analyzes the different travel patterns of vehicles through an intersection, then determines the range of an intersection dynamically and reasonably, and obtains traffic flow speed and delay at the intersection under different travel patterns using a fuzzy fitting approach. Finally, the average intersection travel time is estimated from traffic flow speed and delay and intersection range in different travel patterns. Wuhan road network data and GPS trace data from taxicabs were tested in the experiments and the results show that the proposed method can improve the accuracy of travel time estimation at city intersections. 相似文献
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AbstractCadastral Traversing.—For cadastral purposes traverses are now being executed with an accuracy wholly unnecessary for even large topographical scales. But since “accuracy” varies from a mile to a micron, according to the viewpoint of the observer, it is advisable to exhibit a cadastral traverse, care being taken that it is not an example of that not very uncommon occurrence in which fortuity apes precIsIon. If the accuracy of the example is somewhat unusual, it can be said with assurance that it is not very unusual. 相似文献
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《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
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《测量评论》2013,45(74):155-161
Abstract60. The three standard or field reference tapes are stored at the N.P.L., Teddington, and standardised to class “A” accuracy immediately before and after each base measurement. In order to reduce the residual contraction or “creep” of in var when exposed to higher temperatures, the tapes are retained for as short a time as possible in the Sudan and since 1945 they have been transported in both directions by air. In this way, any “creep” should be revealed by the standardisation after a measurement. From the formula of Dr. Guillaume the ultimate shortening, in the temperatures prevailing at Meheisa and Husheib, would have been ?26 and ?20 × 10?5 ft. respectively and it is clear from Table 3 that this tiresome source of uncertainty is largely eliminated by the procedure adopted. 相似文献
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《测量评论》2013,45(22):460-469
AbstractSo much for the system. Now to describe the method of survey. Between 1902 and 1906 a chain of triangulation, extending from Zanzibar by way of the southern border of what is now Kenya Colony, and the northern and western shores of Lake Victoria to the Belgian Congo, had been surveyed by Anglo-German Boundary Commissions under G. E. Smith and Delmé Radcliffe as leaders. In 1902 a base line was measured near the middle of the Buganda Province by officers of the Uganda Survey Department. This was connected by triangulation to the Anglo-German chain, and several new chains were run across Buganda of an order of accuracy generally classified as that of tertiary triangulation. These chains are now known as the Uganda Main Triangulation, and form the backbone of the Buganda Cadastral Survey, popularly known as the “mailo” survey. 相似文献
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AbstractCountersection is a jointure of intersection and resection. In addition to the elementary problem of a single triangle, whereof one angle is intersecting and one resecting—sometimes known as the problem of “lining in”—, there are many others of a nature somewhat more complex. 相似文献
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《测量评论》2013,45(65):131-134
Abstract1. In geodetic work a ‘Laplace Point’ connotes a place where both longitude and azimuth have been observed astronomically. Geodetic surveys emanate from an “origin” O, whose coordinates are derived from astronomical observations: and positions of any other points embraced by the survey can be calculated on the basis of an assumed figure of reference which in practice is a spheroid formed by the revolution of an ellipse about its minor axis. The coordinates (latitude = ?, longitude = λ and azimuth = A) so computed are designated “geodetic”. 相似文献
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《测量评论》2013,45(12):357-367
AbstractThe only essential difference between geodetic triangulation and any other of the fifteen “orders” of triangulation—which were once proposed, and happily rejected, at an International Conference—is that steps are taken to secure the high degree of accuracy necessary over the large areas to be covered. Some of the steps taken to secure increased accuracy may well be used to insure economy in secondary work, as for instance the use of fewer readings of a large instrument, or the use of luminous signals in conditions of poor visibility; while any surveyor may at any time have to connect his work to a geodetic triangulation, using much the same methods. 相似文献
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《测量评论》2013,45(63):14-20
AbstractFor some two months prior to the formation of the two companies, an intensive course of survey training and “refreshing” had been undergone by all ranks in the field sections, culminating in a combined Royal Artillery/Royal Engineer survey exercise from 1st to 10th October, carried out under operational conditions in all respects (even down to a 30-hour non-stop period of “photo-topo” compilation for the map on which the “final shoot” took place). 相似文献
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《测量评论》2013,45(29):425-430
AbstractThe town plans in question are those ranging from the “five-foot” (1/1056) to the modified “ten-foot” (1/500) scales, made by the Ordnance Survey between 1841 and 1894, and then, in principle at any rate, abandoned. This is, I fear, wholly a British matter and profuse apologies are offered to oversea readers. Yet history, repeating itself as usual, may presently add the wider interest to the tale. 相似文献
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AbstractAn 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”. 相似文献