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1.
《测量评论》2013,45(34):226-228
AbstractGenerally speaking there is a tendency for observations to be judeged by the magnitudes of the triangular errors, although the misclosures of the side equations are equally important. This note explains how to formulate a compehensive criterion covering the two types of misclosure and given in terms of the mean traingular ? m for which definite limits are usually laid down. 相似文献
2.
《测量评论》2013,45(49):129-134
Abstract Traverse Computations must be Checked.—A traverse is a chain of points connected by angular and linear measurements. The check on observations is provided by the agreement, obtained in computations, between the terminals of the traverse (terminal bearings and terminal co-ordinates) taken as fixed. This check is not sufficient, however, to serve as a check on the computations. As a matter of principle, computations should be free of errors; there are no limits of tolerance in computational work except for discrepancies arising from inaccuracy of last figures. Secondly, errors in computation may occur that are not revealed by the traverse misclosures, not to speak of compensational errors, the field for which is very favourable in traverse work. 相似文献
3.
《测量评论》2013,45(98):164-177
AbstractIn the past there has been considerable discussion on the above subject in this Review. There is a bibliography at the end of this article in which the full titles of previous articles are given. For brevity, reference to them in the following text is made by number only. Recently, Gulatee summarized present knowledge and asked how other Survey Departments dealt with this matter. Consequently, it was considered that it would be helpful to set out in detail the procedure adopted by the Directorate of Colonial Surveys for obtaining trigonometric heights, with particular reference to primary and seoondary chains and nets. 相似文献
4.
《测量评论》2013,45(12):330-335
AbstractI. These notes are the results of following up in some detail the well-known fact that the horizontal distance between two points at altitude h is greater, by an amount proportional to h, than the distance between the corresponding points at sea-level. Traverses based on rectangular coordinates are considered, with special reference to the residual errors left after adjusting the misclosures of such traverses without first eliminating errors due to altitude. 相似文献
5.
《测量评论》2013,45(60):227-233
AbstractIt has now become a truism that angles in traverses are observed with a far greater accuracy than the sides, and this applies to all categories of traverse work: precise, transit-and-tape, tacheometric traverses, etc. The result of this is that the effect of angular errors on misclosures in co-ordinates is sometimes so small when compared with that of linear errors that it may be considered as negligible. 相似文献
6.
《测量评论》2013,45(50):156-158
AbstractGiven a straight section of triangulation comprising a fairly large number of equilateral triangles, then, if the length of the section is held fixed but the size of the triangles is made to vary, the total displacement of the section is proportional to the root mean square error of the angular observations divided by the square-root of the length of a side of a triangle, Provided there is no pronounced antagonism between the triangular and length misclosures it will be sufficient to substitute the triangular misclosure ? for the root mean square error in the above statement. 相似文献
7.
《测量评论》2013,45(2):66-71
AbstractThe Americans having started this hare suggested at the Stockholm Congress that a certain number of Laplace stations should be considered the hall-mark of any geodetic triangulation wherever situated. It is therefore pertinent, rather than impertinent, to examine the history of the North American datum at Meades Ranch, Kansas, to see whether the American situation is really known in America. 相似文献
8.
Abstract“A Well-Defined mountain, though miles inland and never visited by the surveyors, will often prove the very keystone of a chart which cannot be regularly and theoretically triangulated” (“Hydrographic Surveying”, by Rear-Adm. Sir Wm J. L. Wharton, K.C.B., and Rear-Adm. Mostyn Field, F.R.S. 3rd Ed. 1909, p. 128). To many the reasons prohibiting the occupation of inland stations may be unknown; it may suffice to state that, in the past, British hydrographers have mapped many coastal waters where penetration of the land was at least inadvisable. Since the charts so made were in general sold to the world, seamen of all nations have benefited from the surveys. 相似文献
9.
10.
Guofeng Wu Jan de Leeuw Andrew K. Skidmore Yaolin Liu Herbert H. T. Prins 《地球空间信息科学学报》2010,13(4):235-242
Measurements of photosynthetically active radiation (PAR), which are indispensable for simulating plant growth and productivity,
are generally very scarce. This study aimed to compare two extrapolation and one interpolation methods for estimating daily
PAR reaching the earth surface within the Poyang Lake national nature reserve, China. The daily global solar radiation records
at Nanchang meteorological station and daily sunshine duration measurements at nine meteorological stations around Poyang
Lake were obtained to achieve the objective. Two extrapolation methods of PARs using recorded and estimated global solar radiation
at Nanchang station and three stations (Yongxiu, Xingzi and Duchang) near the nature reserve were carried out, respectively,
and a spatial interpolation method combining triangulated irregular network (TIN) and inverse distance weighting (IDW) was
implemented to estimate daily PAR. The performance evaluation of the three methods using the PARs measured at Dahuchi Conservation
Station (day number of measurement = 105 days) revealed that: (1) the spatial interpolation method achieved the best PAR estimation
(R
2 = 0.89, s.e. = 0.99, F = 830.02, P < 0.001); (2) the extrapolation method from Nanchang station obtained an unbiased result (R
2 = 0.88, s.e. = 0.99, F = 745.29, P < 0.001); however, (3) the extrapolation methods from Yongxiu, Xingzi and Duchang stations were not suitable for this specific
site for their biased estimations. Considering the assumptions and principles supporting the extrapolation and interpolation
methods, the authors conclude that the spatial interpolation method produces more reliable results than the extrapolation
methods and holds the greatest potential in all tested methods, and more PAR measurements should be recorded to evaluate the
seasonal, yearly and spatial stabilities of these models for their application to the whole nature reserve of Poyang Lake. 相似文献
11.
《测量评论》2013,45(30):457-462
AbstractIn the original geodetic series in Southern Rhodesia—completed by Mr Alexander Simms in 1901—the geographical coordinates of all stations were referred to the point SALISBURYas origin. The coordinates of SALISBURY were fixed by interchange of telegraphic signals with the Royal Observatory at the Cape for longitude, combined with astronomical determinations of time, latitude, and azimuth (see Vol. III, “Geodetic Survey of South Africa”). 相似文献
12.
Abstract Azimuth.—The method was that of star altitudes in the prime vertical, except at X. 34 where hour angles on the P.V. were observed. At B.P. 79 and 99, NE. Terminal, and X. 12 and 34, the measures were made by Major Godfrey-Faussett or Capt. Taylor with the 8-inch C.T. & S. micrometer theodolite; and at all other stations by Capt. Taylor with the Tavistock theodolite Y. 2304. 相似文献
13.
《测量评论》2013,45(35):275-279
Abstract Triangulation.—Apart from Simms' Geodetic Chain, Gordon's Chain, the Copper Queen Limb, and a section of the Victoria and Umtali Series, all the primary triangulation shown on the accompanying map has been executed since 1933. The work of Simms and Gordon has been remodelled, however, being greatly strengthened, and these chains are now called Simms' and Gordon's Series. For an explanation and plan of the above Series, see “A Note on the Trigonometrical Survey of S. Rhodesia”, in the Empire Survey Review, no. 27, vol. iv. 相似文献
14.
Soetkin Vervust Manuel Claeys Boùùaert Bernard De Baets Nico Van de Weghe Philippe De Maeyer 《The Cartographic journal》2018,55(1):16-35
The eighteenth century Carte de cabinet of count de Ferraris is the first large-scale (1:11?520) topographic map of the entire Belgian territory, making it a valuable source of historical information. In the past, a number of studies have tried to assess the geometric accuracy of this map, but they all suffer from restricted technical capabilities for computing and visualizing the distortions, and most of them only focus on a limited number of the 275 map sheets. This paper therefore seeks to provide the first systematic and in-depth investigation of the map’s local geometric accuracy. Recently, two Belgian government agencies georeferenced the Flemish and Walloon part of the Carte de cabinet with a high level of detail, using some 30,000 ground control points to link the old map to the modern topographic map of Belgium. These data sets represent a new and unprecedented potential source of accuracy information. However, the high number of control points and our desire to compute distortions in an exact, local, quantitative and continuous way meant prominent techniques for studying the geometric accuracy of old maps, such as displacement vectors, distortion grids, triangular nets and the popular MapAnalyst software, were unsuited for this task. To meet all our requirements a new technique called Differential Distortion Analysis, which is influenced by the treatment of distortions in map projection theory, was used instead. Its advantages, structure and application to the Carte de cabinet are discussed in detail. The new technique allows calculating and displaying the map’s local angular and surface distortions with a very high spatial resolution. Consequently, it was possible to identify trends in the obtained levels of accuracy and to relate these to historical facts about the Carte de cabinet’s production process. This has resulted in important new insights into the map’s geometric accuracy. 相似文献
15.
《测量评论》2013,45(9)
AbstractThe following method will be found better and quicker than the usual logarithmic process in computing the co-ordinates of intersected points in minor triangulation and traverse work. Let A and B be two stations whose co-ordinates (x 1 y 1), (x 2 y 2) are known. Let P be an intersected point whose co-ordinates (x, y) we wish to determine. Let α and β be the observed angles at A and B respectively. 相似文献
16.
《测量评论》2013,45(35):270-274
AbstractAn instrument was previously described in the Transactions of the Royal Society of S. Africa for the setting of pairs of photographs, taken from air stations, in correspondence; that is, in the same relative positions that the camera occupied in space at the moments of exposure. The principle of the instrument may be recalled. 相似文献
17.
The optical astrometric data of the years 1962–1982 have been reduced once again at the Bureau International de l’Heure (BIH) in order to redetermine the Earth Rotation Parameters (ERP). This new reduction is based on serie largely revised by the stations since their use in the operational work of theBIH, and on some series which were not available previously.
A total of 113 stations is considered, totaling nearly 500,000 measurements of time or latitude. TheERP are determined at five-day intervals.
A new approach is developed: the catalog and local errors are analysed and corrected as group unknowns, which values are adjusted
together with the main unknowns.
The results obtained in the new reduction are compared to other series obtained by astrometry and space geodesy. 相似文献
18.
《测量评论》2013,45(60):221-227
AbstractIn a previous article in this Review, the writer endeavoured to show that chains of minor triangulation could be adjusted by plane rectangular co-ordinates ignoring the spherical form of the earth with little loss of accuracy, provided that the two ends were held fixed in position. It was demonstrated that the plane co-ordinates produced by the rigorous adjustment between the fixed starting and closing sides, differ by only a comparatively small amount from the projection co-ordinates produced by a rigorous adjustment on the Transverse Mercator projection. The saving in time when computing by plane co-ordinates as opposed to rigorous computation on the projection by any method will be apparent to any computer with experience of both methods. 相似文献
19.
Yixuan Tu Shunlin Liang Xiangqin Wei Yunjun Yao Xiaotong Zhang 《International Journal of Digital Earth》2020,13(4):487-503
ABSTRACTA fractional vegetation cover (FVC) estimation method incorporating a vegetation growth model and a radiative transfer model was previously developed, which was suitable for FVC estimation in homogeneous areas because the finer-resolution pixels corresponding to one coarse-resolution FVC pixel were all assumed to have the same vegetation growth model. However, this assumption does not hold over heterogeneous areas, meaning that the method cannot be applied to large regions. Therefore, this study proposes a finer spatial resolution FVC estimation method applicable to heterogeneous areas using Landsat 8 Operational Land Imager reflectance data and Global LAnd Surface Satellite (GLASS) FVC product. The FVC product was first decomposed according to the normalized difference vegetation index from the Landsat 8 OLI data. Then, independent dynamic vegetation models were built for each finer-resolution pixel. Finally, the dynamic vegetation model and a radiative transfer model were combined to estimate FVC at the Landsat 8 scale. Validation results indicated that the proposed method (R2?=?0.7757, RMSE?=?0.0881) performed better than either the previous method (R2?=?0.7038, RMSE?=?0.1125) or a commonly used method involving look-up table inversions of the PROSAIL model (R2?=?0.7457, RMSE?=?0.1249). 相似文献
20.
《The Cartographic journal》2013,50(2):115-116
AbstractAn assessment is made of the accuracy of the map and written survey, which is essentially a list of land-holders and the areas held by each, and of their mutual consistency. The geometry of the map is compared quantitatively with that of the first edition (1852) Ordnance Survey 6-inch (1 : 10 560) map. The Saxton map is found to have a scale of 1 : 5140, leading to the conclusion that the perch used in the scale bar represents 71/9 yards or thereabouts. The areas quoted in the written survey are consistent with acres based on this value. The positional accuracy of points on the map is found to be ～20 m, and areas of typical plots determined from the map are uncertain by between about 4 and 12%. The relationship between these two facts can be understood through a detailed study of the statistics of the errors in separations of points on the map. The written survey is found to omit a substantial number of plots of land from its listings. The map thus appears to be more reliable overall than the written survey. 相似文献