摘要:

AbstractThe accuracy of pointing to stars in astronomical observations for latitude, longitude and azimuth determinations with single-second and geodetic theodolites is investigated, especially with regard to the effect of the angle between the star's path and the crosswires and also the star's rate movement. The investigation includes 1440 observations to artificial stationary stars, nearly 5000 observations to real stars in preselected positions and also determination of circle graduation errors, personal equation etc. The results indicate that the two factors mentioned above do influence the pointing accuracy and that in selecting stars for precise astronomical determinations, the angle of the star's path deserves consideration.

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.242

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractIt is shown that while the Bowditch adjustment is essentially a shearing process which may produce large corrections to the first and last angles of a traverse, the loss in precision, when compared with a least-squares solution, is not serious. Furthermore when there are large differences between the Bowditch and least-squares corrections to the coordinates of stations of L-shaped and square traverses, the least-squares solution is sensitive to the ratio of the variance of distances to that of angle measurement, used in the adjustment.

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.253

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

摘要:

AbstractSince the first infra-red distancers were exhibited in July 1968 at the International Society of Photogrammetry Congress in Lausanne, the electronic distancer has ceased to be regarded by the practising surveyor as a mysterious instrument which could only be used by specialists. There is no doubt that modern electronic distancers can nowadays be used economically for day to day survey work [1]. Since 1968, the number of distancers available for ranges up to 1000 m has increased. Most of these instruments use an infra-red carrier wave with a wavelength of about 0.9μm, i.e. that portion of the infra-red spectrum next to visible light. The chief reason for using infra-red as a carrier wave is the ease with which the GaAs diode—which is normally used as the source of radiation—can be modulated. Unlike incandescent or gas-discharge lamps, the GaAs-diode can be modulated directly in the high-frequency range by varying its supply current. Other advantages of infra-red radiation with regard to absorption and atlnospheric scatter are, however, c,f subordinate importance. The 0.9μm wavelength is near that of visible light and, except in haze where it has a slight advantage, its extinction characteristics (i.e. loss of range in practical terms) in mist and fog are hardly different from those of visible light. It is true that the infra-red portion of the spectrum (wavelengths from about 0.7μm up to about 1mm) includes certain wavelengths with good penetration characteristics in certain types of mist [2, 3], but they are not yet used for distance measuring instruments.

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.273

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.281

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.285

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.287

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.288

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor

ISSN:0039-6265    

DOI:10.1179/sre.1972.21.164.i

出版商:Taylor&Francis    

年代:1972

数据来源: Taylor