Gps-of Rtk Technology Applied Research In The Digital Measurement Of The Dianchi Lake

GPS is a satellite positioning system that was developed by the United States army in the 1970's. The major purpose in that time was to provide the real time and all-weanther navigation service in the whole world including the three domains of land, sea and air. With the rapid development of GPS technology and its receiver, GPS has got an extensive application in the surveying positioning field.RTK is the acronym of the real-time kinematics. RTK employs the data communication link to transfer the original observation data or the phase correctiondata of the known reference station, so the geometric relation between the known reference station and the unknown point can be calculated in the way of online or real-time through RTK. With this technology, the mobile GPS receiver can get the accurate position. In the range of 20km at distance to reference station, the position accuracy is 1-5 cm; the accuracy of the base line is l-10ppm. The accuracy of RTK is related to the algorithm. Therefore , if we use the same data communication link, the algorithm can decide the positioning accuracy and the positioning speed.After many investigation researches, we consider that the GPS with RTK technology is the most economical and the most effective way in such a wide lake as Lake Dianchi.The underwater topographic survey in Lake Dianchi employed the dual-frequency GPS with RTK technology, which type is American TRIMBLE 4700, for horizontal positioning f and the type of the fathometer is Wuxi Haiying SDH-13D;the navigationsoftware: The South 5.0.Because the elevation data we have acquired through GPS is too variable to satisfy the mapping accuracy requirement the elevation value is solved by the waterlever observation in the hydrology station and datum horizon correction of sounding observation.According to the GPS receiver and the fathometer capability and requirement, the correlation index of data interface is: The sounding data is gathered 2 times per second, and GPS data is gathered 1 time per second. The data both surveyed uses navigation software to record in the database display on the navigation map in computerautomatically, and draw out the real navigation course . Through the post processing of the collected data the mathematic mould and the digital map. are automatically formed by the mapping software in computer and the other correlate function can also be realized, on the above digital mapThere are 300 square kilometers of the underwater topography surveying in Lake DianChi with the GPS-RTK technology. And with its result, 1:2000 digital maps of the surroundings in Lake Dianchi are minified to 450 square kilometers 1.10000 digital maps. This paper will deal with the theoretical principle of the applied programs the methods of the underwater topography surveying and the principle of the data processing program and digital mapping program, analyze the rationality and operability and automatic extent of the outside and inside working methods and the data processing program . According to the working experiences, this paper generalizes a low cost, practical and automatic method of underwater topographic survey hi inland lake and river basin.