共查询到20条相似文献，搜索用时 46 毫秒
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《测量评论》2013,45(50):161-162
AbstractThe article on the above subject by Mr. H. F. Rainsford (E.S.R., vi, 45, 404–407) investigates very thoroughly one error in catenary taping, but overlooks two other equally serious errors, namely the uncertainty of the weight of the tape and the uncertainty of the tension applied to it. 相似文献
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《测量评论》2013,45(70):344-351
AbstractIn 1945 I was sent down to Yambio in the southern Sudan to carry out a detailed large scale survey of an area scheduled for the headquarters of an extensive development programme known as the Zande Scheme. The area is not far from the Nile-Congo watershed and the ground is very uneven, covered by ant-hills, and clothed in tall grass and thick bush which includes trees nearly a hundred feet high. Surveys of this kind had not been executed, in the southern Sudan previously except in towns. Nearly all the available experience of cadastral survey work in the Sudan,was therefore based on the very open and flat conditions of the north, where chaining along the ground is the natural and best way of measuring distances within the accuracy required. Except for the geodetic base measurement gear there was therefore nothing in the way of catenary apparatus available, though it was obvious that this would probably be the best equipment for the conditions to be expected in the south. However I had been engaged for most of my survey career up to this time on surveys of a more exploratory nature on much smaller scales such as 1/250,000, and I was unwilling to start experimenting until I had gained some experience in large scale work. 相似文献
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《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
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《测量评论》2013,45(32):92-93
AbstractIt is laid down in the Survey Rules of Northern Rhodesia that all areas to be alienated under freehold title or long lease must be surveyed by triangulation and that traverse methods must not be employed without the permission of the Commissioner for Surveys. This of course is all very well under normal text-book conditions, but there comes a time when triangulation is neither safe nor economical. Such conditions prevail in the Copperbelt districts of N. Rhodesia, where the bush is thick, the terrain more or less flat and the haze usually considerable. To make things a little more difficult the countryside is littered with anthills, both small and large; some as much as 30 feet high and 100 feet in circumference at the base. Traversing under these conditions can be very interesting and at times definitely backbreaking. 相似文献
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《测量评论》2013,45(66):166-174
AbstractThe 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. 相似文献
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《测量评论》2013,45(1):12-15
AbstractDuring recent years a light apparatus has been made up in the Survey of India to provide a basis for minor triangulation. The idea originated with the writer when executing rough triangulation under war conditions, when the need was felt for checking work which had become liable to development of considerable error. The terrain was not such as to allow the measurement of an ordinary base of such a length as half a mile; nor were other facilities present. Accordingly a length of 200 feet was marked out, with the help of a 100-foot steel tape, on a fairly smooth site on rolling ground; and its subtended angle at a distance of about 1500 feet was measured carefully with numerous repetItIons. This 1500-foot length was in turn extended in a similar way to a 3-mile side of the triangulation. No great accuracy was looked for, but enough to rule out the possibility of gross mistake in the irregular triangulation. 相似文献
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《测量评论》2013,45(96):70-75
AbstractThe following paper describes some of the results obtained on it, tour of the Katsina and Kano Provinces of Northern Nigeria between November 1953 and February 1954. The purpose of the tour was to obtain latitudes and longitudes by astronomical observations for air photo mapping control in the northern parts of these provinces where triangulation is not available. The area is mostly flat and sandy. 相似文献
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《测量评论》2013,45(72):67-74
AbstractSince 1899 cadastral mapping in the Sudan has been concentrated along the banks of the Nile from the Egyptian frontier to latitude 13°N., in the towns, and in the area of the Gezira, south of Khartoum, where cotton has been developed. These surveys were controlled by theodolite and steel tape either in the form of traverses or rectangulation. The early triangulation was used mainly to control topographical surveys, for it was essential to cover the whole country as rapidly as possible with a series of maps on scale 1: 250,000. As a consequence much of this early triangulation is of a relatively low order of accuracy, indifferently marked on the ground, and unfit for inclusion in a framework for medium and large scale mapping. 相似文献
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This paper presents a multi-feature based system calibration method for estimating the boresight angles of a land-based mobile mapping system (MMS) comprised of multiple two dimensional (2D) scanners. The method invokes a least-squares adjustment (LSA) to simultaneously estimate several sets of boresight angles for multiple laser scanners incorporated in an MMS as well as the parameters associated with one or more types of geometric features. This is achieved by constraining the groups of feature point clouds captured by multiple runs to fit their corresponding geometric models in such a way that the weighted sum of squares of adjustment residuals is minimized. The method is particularly suitable for in situ calibration because the geometric features involved are commonly occurring structures (e.g. building façades, bridge surfaces, highway signs and hanging power cables) that are usually captured during the actual survey. In addition to using a planar feature model for calibration, a novel and rigorous three-dimensional (3D) catenary curve model is proposed for geometric modelling of hanging cables to augment the calibration. The proposed calibrations were examined with several different combinations of groups of planar and catenary features and the resulting analysis suggests that the in situ calibrations are effective when compared to the manufacturer’s dedicated calibration, with the overall point cloud accuracies for plane fitting being 5.5 cm and 5.4 cm for the vertical and horizontal directions, respectively. It has been successfully demonstrated that the proposed method can be used in a scene having no building façades but only some long hanging cables and horizontal ground surfaces. This is particularly useful for rural areas or inter-city/provincial highways where building façades cannot commonly be captured. Parameter correlations in the calibrations were also addressed. It has also been shown that using catenary features in addition to planar features for the calibration can help de-correlate some parameters and improve the overall accuracy. The in situ nature and the high flexibility of integrating different features of the calibration make the proposed method straightforward for most end-users. 相似文献
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Abstract The recently launched SPOT 1 satellite belongs to a family of second generation remote sensing spacecraft which has been designed to ensure more than 10 years of continuity for the corresponding data delivery. Starting with the model 1 of the satellite series, the paper describes successively its sun synchronous orbit, the 2 identical imaging instruments and the other subsystems such as the on board tape recorders, the telemetry package, the stabilization equipments and etc. Special emphasis is given to the technological innovations put into the design of this satellite, and its twin model 2, with respect to the first generation satellites represented by the three first spacecraft of LANDSAT Series. The paper then details the improvements carried out on the design of the 3rd and 4th models, to ensure the service continuity beyond 1990, and to deliver even more powerful data in terms of potential applications. 相似文献
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《测量评论》2013,45(37):429-436
AbstractGauss's method of collimation is usually given scant attention in survey text-books. The following notes are based on experiments carried out at Accra in making a collimation base, the collimator being a Watts 2I-inch self-adjusting level fitted with a parallelplate micrometer. 相似文献
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《测量评论》2013,45(15):14-16
AbstractTHE mapping of flat country from the ground always entails much more work than the mapping of hilly country for the obvious reason that the nearness of the horizon, coupled with the obstruction of trees, buildings, and vegetation, restricts the view, and long lines are not possible. In contrast to this, mapping from air-photographs becomes much more simple when the country is flat, for the photographic projection is not complicated by height distortions, and it is only necessary to correct for distortions caused by the impossibility of keeping the camera perfectly horizontal at the instant of exposure. During the past four years in Bengal and the United Provinces, where the alluvial plains scarcely vary a foot from monotonous flatness, many thousands of square miles have been surveyed photographically, and excellent maps have been made on a scale of 16 inches to 1 mile and are being used by Settlement Officers for purposes of land assessment. 相似文献
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《测量评论》2013,45(44):322-324
AbstractIn the last three years about 250 miles of “precise” traverse have been surveyed in this country to provide control for detail surveys. A brief account of the results may be of general interest. The traverses are situated where trig. points are far apart, and the cost of subsidiary triangulation would have been excessive on account of the flat nature of the country. 相似文献
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《测量评论》2013,45(37):436-439
AbstractOil is usually found on structural folds resulting from movements occurring millions of years ago in the outer shell or crust of the earth. The exact age in years, of course, cannot be determined. Of the several forms of structural folding on which oil is found, the anticline is the most common. 相似文献
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《测量评论》2013,45(31):2-36
AbstractThe method of accurate linear measurement by means of suspended Invar steel tapes or wires has, since its introduction by Jäderin about the beginning of this century, entirely replaced the older methods of base measurement by bars or rods. It is not surprising, therefore, that the theoretical basis of the method—including a determination of the form of the curved tape and of its horizontal projection—should have received close attention. The most valuable recent contributions to the subject, since Benoit and Guillaume's classic work La Mesure Rapide des Bases Geodesiques, are by Professor and Major Henrici and by the late Mr A. E. Young. 相似文献
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《测量评论》2013,45(49):107-116
AbstractThat man is to be envied who can devote many of the best years of his life to the study of a special branch of science and make some advances in it. Such a man will usually receive recognition of the value of his labours from his fellows in the world of science, and this was certainly the case with Colonel Clarke. The excellence of his many years' work on geodetical subjects, such as thereduction of observations, formulre for the spheroid, figures of the earth, standards of length, and similar matters, was fully appreciated by scientific men during his lifetime, in this country as well as abroad. Curiously enough, his name does not appear in the “Dictionary of National Biography”, though he is, perhaps, the best known of British geodesists. A paragraph is devoted to him in recent issues of the “Encyclopredia Britannica”, but this paragraph is, in one respect, inaccurate. One may say that geodesy makes little appeal to the ordinary citizen, who usually would not know what it is all about. 相似文献
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none 《The Cartographic journal》2013,50(1):51-52
AbstractThis paper shows an experiment with tactile maps designed for visually impaired persons. Tests were carried out on a tactile map produced with 3D printing and including a new type of tactile symbols, volumetric symbols (3D). These symbols are localized faster than conventional flat relief symbols, with the same error rate, an improvement in the use of these tactile devices. Moreover, following tests, differences were found between types of participants with blind participants generally carrying out the proposed tasks better than the rest of users. 相似文献
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《测量评论》2013,45(3):129-131
AbstractThe 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. 相似文献
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Parcharidis Issaak Nikolakopoulos Konstantinos Serelis Konstantinos Baskoutas Ioannis 《国际地球制图》2013,28(3):17-23
Abstract The usefulness of integration of SAR (ERS-1) and Landsat TM data for study active faults and the corresponding displaced landforms in flat or almost flat areas has been demonstrated. The study area is the Kozani basin which in May 13, 1995 was affected by a strong earthquake (Ms=6.6). After co-registration and resampling the two data sets were merged to form a combined image. The combined image offers the spectral characteristics of the TM data with the spatial resolution and roughness sensitivity of SAR images. The merging method used was the IMS to RGB transform. The criteria and parameters examined were geomorphic features, drainage network analysis, slope processes, terrain analysis, and observations on spatial distribution of soil cover as well as linear features that correspond to fracture zones crossing the basin. The use of the combined image allowed us to identify tectonic terraces in the basin produced by activity of normal faults located in the adjacent relief zone. 相似文献