Validation of the Sydnet, continuously operating reference stations for use in global navigation satellite system surveying

摘要

[Abstract]: Permanent Global Navigation Satellite System (GNSS) networks of Continuously Operating Reference Stations (CORS) are becoming routinely used for surveying activities, including maintenance of the geodetic datum, deformation monitoring and land surveying. These networks consist of several fixed GNSS antennas and receivers that operate on a 24-hour basis and provide positional information to those who request it. Before a network can be used in survey application it must be validated to ensureudthe results required for specific tasks are achievable.ududThe NSW Department of Lands (DOL) has developed a network of CORS, predominantly covering the Sydney basin called Sydnet. The network objective was to provide a user with centimetre accurate coordinates, regardless of their position, using static and real-time kinetic (RTK) applications. This dissertation tested and validated the coordinate information provided by Sydnet against class 2A and class B for horizontal and class LB and class LC for AHD heights of coordinated permanent survey marks found in the northern suburbs and northern beaches of Sydney. The outcome determined whether the information provided could position a user with an accuracy and precision that isudacceptable under current legislation.ududThe aim was to evaluate and critically analyse the horizontal and vertical results of GNSS observations using Sydnet with respect to accuracy, precision and reliability.ududResearch into the Sydnet system was critical to determine its functionality and limitations before, a network of control marks was planned to test these limits. The test network was based on careful planning to ensure that the special selection of known coordinated survey marks chosen, provided the necessary geometry along with mocking field simulated situations i.e. sky obstructions. The essentialudfield observation data was collected in a manner that conformed to the ICSM SP1 standard to make certain the best possible outcome for tests 1 and 2 were achieved which were as follows:ududTest 1: Rapid static GNSS observations undertaken were to comply with a Class B survey requiring two occupations of seven of the eight marks in the network and three occupations of the eighth mark all for a half hour period.ududTest 2: Real-time static application occupied each mark in the network firstly, for a ten minute period from two separate base CORS and secondly, for a one minute period from the same two base CORS on a separate day.ududThrough Leica Geo Office and Microsoft Excel software, the data was processed to determine observed values at each network control mark, and then compared with the true value of each mark, with the final outcome determining Sydnet’s accuracy, precision and reliability.ududAnalysis of results has proven that Sydnet can be used as a reliable GNSS tool for two-dimensional surveys at present provided that certain procedures are adhered to. Heights provided using Sydnet have proven less than adequate in both accuracy and precision tests and if possible other methods should be used for project completion until the systems refinement. The tests for reliability proved aud94% solution rate, which provided confidence in gaining a solution during field operations.