Surveying with GPS for Construction Works Using the National RTK Reference Network and Precise Geoid Models (original) (raw)

The paper discusses surveying by means of RTK-GPS positioning techniques in construction work with emphasis on using a single GPS receiver. The use of the traditional RTK GPS method is first discussed, followed by outlining the principles and advantages of using RTK reference networks. Possible applications of these techniques in the construction field are given. A system consisting of a triad of three cheap orthogonal laser pointers is presented for rapid setting out of surveying marks and for minimizing the number of points occupied by GPS during night work. The system can be used to set out several points along and perpendicular to any line on the site. A model is also presented for transferring map distances derived by the GPS grid coordinates to their respective ground distances. The presented techniques were evaluated during construction of a large building and its access road. Measurement corrections were employed from a national RTK network in Dubai Emirate, UAE. The RTK GPS method was also used for determination of instantaneous orthometric heights from GPS ellipsoidal heights and geoid heights. The latter were interpolated from a recently developed precise gravimetric geoid model for Dubai. In addition, the GPS was used for instantaneous determination of a total station location working on the site, by mounting the antenna directly on top of the total station alidade; thus eliminating the need for establishing permanent horizontal control stations. Results showed that positioning accuracy of 1-3 cm was generally achieved. Repeatability results showed, however, that cm-level differences in coordinate estimation can still be experienced between different observing sessions. Thus, this method is appropriate for medium accuracy construction surveys, such as grading and staking out of road marks, footings, pipelines, utilities, landscapes and fences.

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