Design And Implementation Of Data Acquisition System With High-precision GPS Timing

Mobile Mapping System is a new type of spatial information measurement system. Itperforms well on automation, high-speed, real-time and high-precision Measuring, hasbeen widely used in the measurement of the modern road space information. MMS isequipped with GPS, INS (inertial navigation system), CCD camera, high-speed videocameras, laser scanners and other sensor devices to collect spatial information. Dataacquisition device is the core of the MMS. It’s required high time synchronizationperformance, able to adapt to bad environment and the ability to collect data continuouslyfor long time. The traditional data acquisition equipment based on data acquisition cardand industrial computer is unable to meet the requirements of the modern MMS system.In this article, a new type of data acquisition system based on FPGA and embeddedmicroprocessor has been designed in order to meet the requirements of MMS. At first, webuilt a data acquisition system based on Cyclone FPGA and MPC8313PowerPC, andcompleted the hardware design. And then, we proposed an implementation method of GPStiming. In order to solve the problem of the frequency drift and aging of the local oscillator,we introduced the crystal tame algorithm to calibrate the local oscillator. In order toeliminate the random jitter of the1PPS sync pulse given by the GPS receiver, weintroduced Kalman filter to eliminate the random noise and improve the timing accuracy.At last, we described the process of data acquisition using the SICK laser radar and thecorresponding logic design.The test results show that the time accuracy of this system is very high, and thepacket loss rate is very low. The data acquisition system designed in this article can meetthe requirement of the MMS; it has high practical value and very good reference value to thesimilar systems.