Research On Data Acquisition And Processing Of Point Cloud In Medium-range 3D Laser Scanner

In view of the urgent needs of the rapid establishment of physical model,underground space mapping,landslide earthwork estimation and other projects,as well as the development of laser ranging,precision motor control,digital image acquisition and many other science and technology,3D laser scanning technology came into being.3D laser scanning measurement uses the laser to range,guides the laser beam to sweep the target area in the set speed through the high-precision servo control system,obtains a series of continuous distance and image information and uses the post-processing software to solve 3D coordinates and express the texture.As the technology has high precision,high efficiency,wide range of application and other characteristics,more and more industries are concerned about it.At present,the domestic 3D laser scanning market mainly imports the expensive foreign equipment.Due to the restriction of the high cost in equipment purchase,the promotion of the 3D laser scanner is slow.Therefore,it is urgent to design an economical and practical 3D laser scanning product.Start with study in the acquisition and treatment of data cloud,this paper uses Visual Basic6.0 platform to realize the serial communication of laser radar and stepper motor and control them to operate cooperatively to complete a series of distance data acquisition,uses polar coordinate method to calculate the 3D coordinates combining with the distance and angle and realizes the point cloud pseudo-color rendering and multi-site cloud stitching and other operations.The main contents are as follows:1.Start with the hardware and software of 3D laser scanning measurement,the paper describes the type and application of 3D laser scanner,the laser ranging principle and 3D laser scanning working principle and scan notes detailedly.2.In order to achieve the 3D data acquisition,the paper studies the hardware selection,serial communication,software design and other aspects.The realization process is: fixes the two-dimensional laser radar on the precise electronic control rotating platform to establish a 3D scanning hardware environment;uses the MScomm control provided by the Visual Basic 6.0 to control motor rotation and radar ranging;sets the motor's rotation angular speed to drive the laser radar achieve rotation measurement,calculates the angle of the adjacent laser beam combing with the laser radar scanning interval and the electronic control platform speed and calculates the 3D coordinates of the scan area using the polar coordinate method combined with the distance and angle.3.Because the computer system uses the non-precision timing,the calculation of the 3D coordinates has larger error,this paper uses the calculated length of the regular structural surface to minus the length of the structural surface which is measured by high-precision total station,assigns the error to each line in the scanning range to reduce the impact of the error and pseudo-color render the point cloud to enhance visual effects.4.In order to evaluate the precision of scanning point cloud,the paper uses the high-precision total station to obtain the length of the marker as a real value.The results of comparing with the scan results are that: when the ranging is about 10 meters,the precision is about 2cm;when the ranging is less than 5 meters,the precision is better than 1cm.Using the 3D laser scanning equipment can survey the 3D coordinate quickly,obtain complete physical model by splicing multi-station scanning data of the same target,which verifies the feasibility of the related techniques and method in data collection and treatment.