| Precision is the basis of surveying, surveyors organize the surveying work according to the request of precision ,and apprise the precision of the production. With the development of survey equipment ,the precision of surveying has been approved. Still ,the precision of surveying work is the concern of surveyors.GPS(Global Positioning System) is developed by USA government ,it is able to give three-dimensional coordinates with high precision. It had initial Operating Capability in December 1993. With the development about twenty years the applications of GPS increased and the researchers increased too. RTK(Real Time Kinematic) is the developed from the GPS technology .Different from GPS static observations, RTK needs no data processing after the outside work and can give coordinates with a precision at centimeter level. With the advantages of real time processing and high precision, RTK has been applied in many areas such as topographic drawing, highway surveying , railway surveying and pipeline surveying . The popularization of RTK creates the condition for its deep research .The researchers focus on the factors which have effect on RTK such as the ionospheric effect,troposhperic effect and multipath effect. They suggested these effects can be eliminated by using the method of differential technology when the distance of basis station and rover station is not longer than 20 kilometers. The multipath effect is proved to be a periodic error at the same place and same time of different days by analyzing the long time observation of GPS. In order to lower the effect of multipath , we can use a ground plane antenna or use the correction which is caculated from the data the day before. In this thesis , using the method of experiment we analyzed the regularities of distribution; using RTK height to supersede the traditional level height in small area; the precision difference caused by different measument update method. We reach conclusions as below:1.By analyzing the coordinates datum collected by RTK(Trimble R8 GPS receivers) , the horizontal coordinates in the contingent value within±20mm. The Elevation changes in the contingent value within±30mm . The changes is evident when the sample number is small ,as the number of sample reached a certain number it become more and more unconspicuous. Take Trimble R8 GPS receivers for example ,by one second sampling interval ,collected 5000 coordinates ,when the sampleing number reached 1500 the change of horizontal coordinate change became unconspicuous , when the number reached 2500 the elevation change became unconspicuous .This conclusion is worthful for determining the observation time according to the precision request.2.By establishing a small height control network (500m×600m),we investigated the change of height anomalies. We took two method for comparision and found the result of using plane fitting method was not very good ,the fitting accuracy is about 24.8mm. When using the method of considering the geoid parallel to reference ellipsoid, the fitting accuracy is about 20.5mm. When the survey area is small we can suppose the height anomalies is same.3.According to the result of experiment , the method of using RTK normal precision and the geometry location is feasible. This conclusion can help the surveyors do the design.4.Increase the sample number of datum collected by RTK ,and use the mean as result can improve the precision of surveying.5 . Do experiments between two method of coordinate correction (Basis-Rover, Rover-Rover),analyzed the precision of the results. It is proved that using the control points of short distance increased the error as the distance increased between basis station and rover station. And the surveying result using Basis-Rover method did better than the other one . According to the conclusion drew by the experiments, we can see the RTK horizontial precision is better than elevation precision. The method of using RTK to take place of level surveying is not efficient for small area. Using different method of coordinate correction may cause the lost of precision. The result fo this phenomena is obvious when using two control points within 100 metres far from each other. To achieve certain precision ,we must not use control points with short distance. This thesis used the method of analyse estimate the error of RTK surveying, and it had been proved effective. The thesis do the reseach of RTK according to practical work ,and the conclusion have guiding significance.
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