新大地坐標(biāo)數(shù)據(jù)管理系統(tǒng)的開發(fā)畢業(yè)論文外文翻譯-在線瀏覽
2024-07-24 01:09本頁(yè)面
【正文】 c starting reference data． Then a point in Beijing was calculated accordingly and was so called 1954 Beijing coordinate system． Since the founding of the state， a lot of surveying and mapping tasks were pleted with this coordinate system despite some problems existed due to the technological restrictions at that time． These prob1ems are： （ 1） The reference ellipsoid semimajor axis is more than 100m longer than modern precisely surveyed size． （ 2） The reference ellipsoid used is not identicall with the geoid of our counter． The elevation abnormity in Eastern is as high as 177。68 m． （ 3） The ellipsoid reference axis direction is not precisely defined． （ 4） Error accumulations are large and accuracy is low． To overe these problems and provide better services for economic development， national defence， and geodesy as well as space research， the Nation． al Surveying Bureau did adjust in one cast to national astronomic geodetic work in the end of 1970s and the beginning of 1980s． The 1980 Xi’an coordinate system was developed． IUGG75 ellipsoid was used in this system． The difference between ellipsoid and geoid is within 420 m and the side accuracy is 1/500 000 after adjustment． A new geodetic coordinate system is planning to meet the scientific needs in our country as the developments of new technologies such as very long base interfere(VLBI)and global positioning Systems(GPS)． The classes A and B GPS work were pleted and put in use respective in 1996 and 1997． The space geodetic work developments entered a new phase with these progresses． It is not only with higher accuracy than former systems but also with three dimension coordinates which developed on internationaly defined ITRF frame． This high accuracy 3D space geodetic coordinate system will guarantee the infrastructure surveying for the first 10 years of twentyfirst eentury． After adjustment， the plate coordinate overlap accuracy of class A GPS work is better than 210。1 m， respectively． The pletion of national class A and class B geodetic control work indicates that we have developed decimetre absolute 3D geodetic control work． A new reference system is available for our space technology， and spatial data as well as real Proceedings of ISM 12th International Congress time dynamic positioning． A lot of local coordinate systems were developed besides national plane coordinate system． These systems served national economic developments in some sense． Considering the importance of coordinate system to economic developments and national defence， coordinate system factors are confidential data． The national and local governments control the geodetic coordinate factors strictly and data processing is also charged by relative government agencies． 2 MODERN SURVEYING TECHNOLOGY REQUIREMENTS FOR COORDINATE SYSTEM MANAGEMENT Requirements with advances and applications Of GPS GPS has been playing an important role in surveying and mapping from 1990 s and the accuracy is getting better． The US GPS real time positioning accuracy is 177。30 m from earlier 177。6 m and charge users177。1 m global satellite positioning system will be available in 2020． The popularly used coordinate systems now in our country are 1954 Beijing system and 1980Xi’an system and 10cal sys
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