Study And Practice Of The Second Urban Land Investigation Based On Digital Surveying And Mapping

The second land investigation, as a major national conditions and strength investigation, the purpose of which is to ascertain the comprehensive land use status, grasp the truth and the basic data of land survey results of information, practice network management, establish and perfect the system of land survey, statistics and registration system, realize the socialization of land resource information services to meet the social and economic development, land macro-control and land resources management needs.For urban second land investigation, the article mainly studied the following problems:(1) Firstly this paper pays more attention to studying the issue of coordinate system and transformation method about GPS data. The result of GPS survey is spatial rectangular coordinates or geodetic coordinates relative to the WGS-84, but the actual result used in the engineering surveying in our country is project (or local) coordinates or Beijing-54 or Xi'an-80 coordinates and normal height. So the result of GPS must be transformed so that it can be used in practical engineering. Hence the geodetic geocentric coordinate system like world geodetic system (WGS-84) which is the frame of GPS surveying data, and the celestial coordinate system which is the frame of GPS satellite ephemeris data has been described and the relationship between the two coordinate systems has been presented. The national reference-ellipsoid-centric coordinate system and local plane coordinates,China Geodetic Coordinate System 2000(CGCS2000) which are the frames of engineering survey has been studied and the relationships in these coordinate systems have been deduced. In the mean time, the relation between the geodetic height which is used in GPS surveying data and the height used in engineering survey has been discussed and the method of transforming height has been generalized, amd some models and methods in common use of coordinates transformation and normal height fitting are introduced and the detail solution to the model is also afforded(2) Secondly this paper discusses the principles,surveying mode and system construction of GPS RTK. The factors which reduce RTK's surveying accuracy are analyzed across-the-aboard and the ways to eliminate or weaken these factors influence are discussed, the application of RTK technology is studied in the second land investigation. (3) To improve urban land investigation in the second time,we carries out a digital cadastral investigation so that some practice and researeh are taken by means of advanced methods in surveying and mapping.The useful conclusions are achieved from the analysis on the current situation of land use by using GPS,total stations,digital mapping software,data base technology and other equipments.