Gps-rtk Applications for Assisting the Engineering Design of Large Structures

Though accelerometers have been used to monitor the deformation/deflection of large structures after they are built, relative displacements between different parts of the structure during severe weather conditions cannot be measured accurately due to the lower band limit of accelerometers. Therefore, the current design of large structures can only be termed as being of a "partially closed-loop design". In order to test the feasibility of a "fully closed-loop design" for large structures, two Leica CRS1000 and two Trimble MS750 GPS receivers have been tested in the Real-Time Kinematic (RTK) mode, with fast sampling rates of 10Hz and 20Hz, to determine how well they measure relative displacements, from very low (DC) to high (10Hz) frequency. In the test involving the two Leica GPS receivers, both the 2.3Hz and 4.3Hz sine signals of 12.7mm amplitude used to simulate structure deformation can be resolved easily from the power spectrum of the RTK time series for the three components (latitude, longitude and height). In the Trimble GPS receiver test, RTK measurements at 20Hz for over three hours, over the same period on five successive days, were recorded to determine whether measurements on consecutive days can be used for noise reduction. The potential for the use of GPS RTK to measure a high frequency deformation signal will be discussed in the light of the tests carried out so far.