Time Synchronization Design And Implementation Based On SICK Laser Scanning System

Laser scanning is a kind of new mapping technology which began from last century. Comparing with traditional manual data obtaining technology, laser scanning has more advantages as its ability of fast gaining accurate and large area data directly. Recently, vehicle-borne laser scanning and modeling system integrated muti-sensors such as laser?IMU? GPS?camera developed rapidly. These sensors integrate through fixed spatial location and time synchronization on stable vehicle so that this vehicle can scan over buildings along moving road and get their3-D information. As different sensors use different frequency and their data updating frequency are different, it becomes a big problem to realize data synchronization among different sensors in the vehicle-borne laser scanning system. This paper proposed a design scheme to solve this problem.In this paper, we use Avantech PCI-1780Data Acquisition Card to realize data synchronization among different sensors, including laser point time and GPS time and IMU time, so that laser point cloud and IMU time can be integrated to GPS time so that all sensors are synchronized. Main works accomplished in this paper are as follows:(1) Based on data obtaining characteristic of Sick laser, this paper accomplished time synchronization of laser point cloud and GPS so that laser point are attached with GPS time.(2) Using PPS pulse of GPS sign and GPS Time sign to realize time synchronization of IMU and GPS.(3) Develop software of time synchronization to make sure data obtaining of different sensors synchronized. And then according the synchronized time, this paper raised time arithmetic of laser point cloud and use MFC to realize auto data rectification of point cloud and GPS.(4) This paper developed two testing program to test accuracy of synchronization between IMU and GPS. Also researchers test time accuracy of synchronization of the whole system and found that it's less than millisecond.