共查询到20条相似文献,搜索用时 484 毫秒
1.
《The Cartographic journal》2013,50(3):269-271
AbstractReal 3D objects are typically explored with high efficiency by several fingers. The largest increase in efficiency is obtained between the use of one and two fingers. The aim of the present experiment was to investigate if the efficiency of identifying a country on a 2D tactile map can be increased by the use of two fingers exploration along opposite sides of the map compared with following along the contour. The result was that there was no significant difference between one-finger and two-finger exploration, but there were significant improvements over sessions. The difference between exploration of 2D and 3D objects is discussed. 相似文献
2.
《测量评论》2013,45(13):391-395
AbstractIn January, 1934, a report was received from the Royal Research Ship Discovery II that the positions of Inaccessible and Nightingale Islands in the Tristan d'Acunha group were incorrectly shown on British Admiralty chart No. 1769. The report originated from local information, and was to some extent confirmed by patent log distances run by Discovery II, and by sea sights, but no really definite evidence as to the correct position of the two islands was received. In effect, the report merely stated that both Inaccessible and Nightingale Islands were considerably nearer to Tristan Island than as charted. 相似文献
3.
《测量评论》2013,45(98):177-184
Abstract1. The Secondary and Tertiary Triangulations of the six counties of Northern Ireland which were observed about 1900 were computed county by county each on its own meridian on a Cassini projection using Airy's figure of the earth. Although a number of points common to two or more counties were fixed no attempt was made to bring the separate counties into sympathy either with each other or even with the old Primary triangulation as adjusted by Clarke in 1856. 相似文献
4.
《测量评论》2013,45(15):55-56
AbstractI regret that my note on this subject (vol. ii, no. 7,PP· 32-3) should have apparently provoked so little comment or interest. I feel that the silence may be either that accorded to my Impetuous Inrush or that produced by alarm at the possible complications to be overcome before theory can be reconciled with practice. If the latter, then my original title is perhaps in some measure responsible. It is really very simple; let two facts suffice. 相似文献
5.
On the multivariate total least-squares approach to empirical coordinate transformations. Three algorithms 总被引:2,自引:1,他引:1
The multivariate total least-squares (MTLS) approach aims at estimating a matrix of parameters, Ξ, from a linear model (Y−E
Y
= (X−E
X
) · Ξ) that includes an observation matrix, Y, another observation matrix, X, and matrices of randomly distributed errors, E
Y
and E
X
. Two special cases of the MTLS approach include the standard multivariate least-squares approach where only the observation
matrix, Y, is perturbed by random errors and, on the other hand, the data least-squares approach where only the coefficient matrix
X is affected by random errors. In a previous contribution, the authors derived an iterative algorithm to solve the MTLS problem
by using the nonlinear Euler–Lagrange conditions. In this contribution, new lemmas are developed to analyze the iterative
algorithm, modify it, and compare it with a new ‘closed form’ solution that is based on the singular-value decomposition.
For an application, the total least-squares approach is used to estimate the affine transformation parameters that convert
cadastral data from the old to the new Israeli datum. Technical aspects of this approach, such as scaling the data and fixing
the columns in the coefficient matrix are investigated. This case study illuminates the issue of “symmetry” in the treatment
of two sets of coordinates for identical point fields, a topic that had already been emphasized by Teunissen (1989, Festschrift
to Torben Krarup, Geodetic Institute Bull no. 58, Copenhagen, Denmark, pp 335–342). The differences between the standard least-squares
and the TLS approach are analyzed in terms of the estimated variance component and a first-order approximation of the dispersion
matrix of the estimated parameters. 相似文献
6.
ABSTRACTWidespread forest fire events occurred in the foothills of North Western Himalaya during 24 April to 2 May 2016 (Event-1) and 20–30 May 2018 (Event-2). Their impacts were investigated on the distribution of pollutant gases ozone (O3), carbon monoxide (CO), and oxides of nitrogen (NOx) over Uttarakhand using simulations of Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and in-situ observations of these gases over Dehradun, the capital of Uttarakhand. During Event-1, the observed CO mixing ratio over Dehradun increased from 25 April 2016 onwards, attained maximum (705.8 ± 258 ppbv) on 2 May 2016 and subsequently decreased. The rate of increase of daily baseline CO was 29 ppbv/day during HFAP (High Fire Activity Period). During Event-2, daily average concentrations of CO, O3, and NOx showed systematic increase over Dehradun during HFAP period. The rate of increase of CO was 9 ppbv/day, while it was very small for NOx and O3. To quantitatively estimate the influence of forest fire emissions, two WRF-Chem simulations were made: one with biomass burning (BB) emissions and other without BB emissions. These simulations showed 52% (34%) enhancement in CO, 52% (32%) enhancement in NOx, and 11% (9%) enhancement in O3 during HFAP for Event-1 (Event-2). A clear positive correlation (r = 0.89 for Event-1, r = 0.69 for Event-2) was found between ?O3 (O3with BB minus O3without BB) and ?CO (COwith BB minus COwithout BB), indicating rapid production of ozone in the fire plumes. For both the events, the vertical distribution of ?O3, ?CO, and ?NOx showed that forest fire emissions influenced the air quality upto 6.5 km altitude. Peaks in ?O3, ?CO, and ?NOx during different days suggested the role of varying dispersion and horizontal mixing of fire plumes. 相似文献
7.
ABSTRACTAtmospheric aerosols can alter the direct and diffuse components of global solar radiation, which further influences terrestrial gross primary productivity (GPP) via photosynthesis. To investigate the impact of aerosols on GPP, GPP is modeled using the Boreal Ecosystem Productivity Simulator (BEPS) under two aerosol scenarios (S1& S2) over cropland and grassland ecosystems in the highly polluted North China. In S1, the aerosol-effect is not considered and an original empirical method is used when estimating direct and diffuse solar radiation in BEPS. In S2, BEPS is improved by a new empirical method which incorporates the impact of aerosols using the remote sensing-based aerosol optical depth (AOD). Results suggest that aerosols can reduce GPP of the sunlit leaves by decreasing direct solar radiation, but increase GPP of the shaded leaves by increasing diffuse solar radiation. The impact of aerosols on GPP is more significant over the cropland ecosystem (p < 0.05) with a more complex canopy structure during the peak period of the growing season. Furthermore, an AOD value of 0.3–0.6 with a diffuse fraction (the fraction of diffuse solar radiation in global solar radiation) around 30-40% can largely increase total GPP over the cropland ecosystem. The study improves the accuracy of GPP modeling using BEPS by highlighting the aerosol-effect on GPP via solar radiation over highly polluted regions.Abbreviations: gross primary productivity (GPP); aerosol optical depth (AOD); boreal ecosystem productivity simulator (BEPS) 相似文献
8.
《The Cartographic journal》2013,50(1):15-26
AbstractThis paper aims to evaluate what effect applying residents' urban image to virtual city design (a real time virtual model of an actual city) has on wayfinding performance during 'flying-based' navigation mode. Two experiments were conducted to compare two virtual city designs using the virtual model of Tel Aviv city. One design included highlighted urban elements from the residents' urban image, while in the second design no highlighted elements were included.The experiments proved that using the elements of the residents' urban image in a virtual city design enhances the performance of all participants in the wayfinding tasks, and especially those with a low level of spatial knowledge. Analysis of the trajectory patterns and the verbal reports of the participants during navigation showed that the urban image design facilitates a more intensive use of a position-based strategy, in addition to the path-integration wayfinding strategy, which was found to be dominant in the virtual model without the highlighted urban image elements. On the basis of these findings we propose principles for designing virtual cities from a perspective of wayfinding. 相似文献
9.
Summary The discrepancy between precision and accuracy in astronomical determinations is usually explained in two ways: on the one
hand by ostensible large refraction anomalies and on the other hand by variable instrumental errors which are systematic over
a certain interval of time and which are mainly influenced by temperature.In view of the research of several other persons and the author’s own investigations, the authors are of the opinion that
the large night-errors of astronomical determinations are caused by variable, systematic instrumental errors dependent on
temperature. The influence of refraction anomalies is estimated to be smaller than 0″.1 for most of the field stations.
The possibility of determining the anomalous refraction from the observations by the programme given by Prof. Pavlov and Anderson
has also been investigated. The precision of the determination of the anomalous refraction is good as long as no other systematic
error working in a similar way is present.The results, which are interpreted as an effect of the anomalous refraction by Pavlov and Sergijenko, could also be interpreted
as a systematic instrumental error.
It is furthermore maintained thatthe latitude and longitude of a field station can be determined in a few hours of one night if the premisses given in [3, p.68]are kept.
It has been deplored that the determination of the azimuth has not been given the necessary attention. It is therefore proposed
to intensify the research on this problem.
The profession has been called upon to acquaint itself better with the valuable possibilities of astronomical determinations
and to apply them in a useful and appropriate manner. At the same time, attention has been called to the possibility of improving
astronomical determinations with regard to accuracy as well as effectiveness. 相似文献
10.
《测量评论》2013,45(58):142-152
AbstractIn January 1940, in a paper entitled “The Transverse Mercator Projection: A Critical Examination” (E.S.R., v, 35, 285), the late Captain G. T. McCaw obtained expressions for the co-ordinates of a point on the Transverse Mercator projection of the spheroid which appeared to cast suspicion on the results originally derived by Gauss. McCaw considered, in fact, that his expressions gave the true measures of the co-ordinates, and that the Gauss method contained some invalidity. He requested readers to report any flaw that might be discovered in his work, but apparently no such flaw had been detected at the time of his death. It can be shown, however, that the invalidities are in McCaw's methods, and there seems no reason for doubting the results derived by the Gauss method. 相似文献
11.
Abstract Introductory.—From time to time the question of the relation between the metre and the foot is raised, most frequently perhaps from Africa. Had there been no more than a single metre to consider the question would no doubt arise but seldom: the most recent authoritative comparsion would be generally accepted. But actually it is the existence of two metres—the “ legal” and the “international”—which complicates the question, so much indeed that there is no metrological factor which has influenced survey, British and foreign, more than the relation between these two metres. The question was discussed in this Review (I, 6, 277, 1932), but memories grow shorter, attention is more diffused, and besides there is required a more explicit statement of the situation as it affects British surveyors, especially in Africa, whence the question has been raised anew. To illuminate it, unfortunately the need recurs to repeat some well-known facts. 相似文献
12.
《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
13.
《测量评论》2013,45(26):234-243
AbstractTHE Gold Coast can now be said to have recovered from the slump which caused such disastrous consequences in 1931–2 and resulted in a heavy reduction in the establishment of the Survey Department. So far there has been no increase in staff, but more badly needed money for buying stores and increasing the labour staff has been available, and authority has now been given for an increase of 12 in the establishment of African Surveyors; this will result in the re-opening of the Survey School in 1937. 相似文献
14.
15.
Kamlesh P. Lulla Michael R. Helfert David L. Amsbury Victor S. Whitehead Cynthia A. Evans M. Justin Wilkinson 《国际地球制图》2013,28(1):69-80
Abstract Multi‐temporal ERS‐1 SAR data acquired over a large agricultural region in West Bengal was used to classify kharif crops like rice, jute and sugarcane. Rice crop grown under lowland management practice showed a temporal characteristic. The dynamic range of backscatter was highest for this crop in temporal SAR data. This was used to classify rice using temporal SAR data. Such temporal character was not observed for the other study crops, which may be due to the difference in cultivation practice and crop calendar. Significant increase in backscatter from the ploughed fields was used to derive information on onset and duration of land preparations. Synergistic use of optical remote sensing data and SAR data increased the separability of rice crop from homesteads and permanent vegetation classes. 相似文献
16.
《测量评论》2013,45(25):140-151
AbstractThe subject of the training of European surveyors has received a great deal of attention in the course of the last two Empire Conferences, but little or no mention has been made of the native surveyor, his education, work, and prospects. The subject is very important, however, and the account of the training of Africans for the N. Rhodesia Survey, which appeared in vol. iii, no. 21 of the Empire Survey Review, was read with considerable interest. It may not be out of place, therefore, to introduce this paper on the means adopted in Malaya to recruit and train an efficient staff of subordinates or “Technical Assistants” as they are termed locally. 相似文献
17.
《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
18.
《测量评论》2013,45(5):207-214
Abstract Artillery Survey.—Included in the term “Artillery Survey are two distinct problems, the first that of determining the “line” and “range” at which fire should be opened, and the second that of laying the gun in the required line. To appreciate these problems it. is necessary to know a little about the technique of gunnery, and for the benefit of those who have no acquaintance with the subject the following brief résumé may be given. 相似文献
19.
Y. Kozai 《Journal of Geodesy》1968,42(3):355-357
From periodic variations of the orbital inclinations of three artificial satellites 1959Alpha 1, 1960Iota 2, and 1962Beta Mu 1 Love’s number of the earth and time lag of the bodily tide due to the friction are determined, respectively,0.29±0.03 and(10±5) minutes in time.
While the previous paper on the determination of Love’s number of the earth (Kozai, 1967) was in press, a minor error was
discovered in the Differential Orbit Improvement program(DOI) of the Smithsonian Astrophysical Observatory(SAO). Since the analysis was based on time-variations of the orbital inclinations which were derived by theDOI from precisely reduced Baker-Nunn observations, it is likely that the results in the previous paper was affected by the error
in theDOI. Therefore, the analysis is iterated by using the revisedDOI. Three satellites, 1959Alpha 1 (Vanguard 2), 1960Iota 2 (rocket ofEcho 1), and 1962Beta Mu 1 (Anna) (see Table 1) are adopted for determining Love’s number in the present paper. The satellite, 1959Eta, which was used in the previous paper, is not adopted here, since the inclination of this satellite shows irregular variations
unexplained. Instead of 1959Eta 1962Beta Mu 1 is adopted as orbital elements from precisely reduced Baker-Nunn observations have become available for a long interval of
time for this satellite. 相似文献
20.
《测量评论》2013,45(12):345-346
AbstractIn the course of his stimulating and suggestive paper in your recent issue, No. ro, pp. 226–38, Mr. A. J. Potter writes on p. 233 “but there is no simple construction by which X can then be found”, and again on p. 237 “a direct construction, if there be such”. This cheerful challenge invites the construction of a circle centred on a given line, passing through a given point thereon, and touching a given circle, and I have found the lure of Mr. Potter's gauntlet as irresistible as its recovery has proved delicate. In order to shoulder responsibility and by no means to claim highly improbable originality, let me confess that the problem is new to me and the two constructions I offer are my own; I venture to hope that Mr. Potter may consider one or other of them not unworthy of his epithet “simple”, though I freely admit the aptitude of his empiric procedure to its purpose. The proofs are not long, but for fear of overshooting my welcome I offer them to anyone for the asking; and for the same reason my diagrams are small and therefore mere. 相似文献