A RESEARCH ON EFFECTS OF DIFFERENT SCANNING RESOLUTIONS DEPENDING ON THE NUMBER OF TARGET USED IN TERRESTRIAL LASER SCANNING

Abstract

Terrestrial Laser Scanners (TLS) are utilized in many application areas thanks to advances in technology. Accuracy and reliability of the outcome obtained through the scanners mostly depend on the resolution and accuracy of the obtained data. Location information as to smallest detail on object can be acquired thanks to point clouds obtained by virtue of terrestrial laser scanners. The point density reflecting the surface of the most appropriate object should be selected according to aim of the work carried out, the desired accuracy, time, cost, present hardware and software as well as the desired outcome. 3 or more than 3 targets have to be employed for transformation of the coordinates obtained from the laser scanner into desired coordinate system. The targets utilized have to be placed appropriately within the scanning area. It has been tried to determine the effects of targets which are used in georeferencing and which are placed in different numbers and directions and the scan resolutions thereof on point location accuracy in this study. For this purpose, a study has been carried out at the Calibration Laboratory of Faculty of Civil Engineering of Yildiz Technical University. Optech ILRIS 3D laser scanner and Leica TPS 1201 total station were employed in the cited application. 12 targets with appropriate geometry were placed in the test area to be scanned. Georeferencing performed by the use of targets with directions and numbers varying according to different scan resolutions and their point positions has been tried to be re- determined. Comparisons were made according to the locations of these 12 target points determined by the Total Station. It has been tried to determine if there was a difference between the point positions obtained by considering the changing number of targets as well as the scan resolution. It has been determined that point position accuracy has decreased depending on the increase of the scan resolution. Choice and number of appropriate targets in addition to direction and orientation of target with respect to each other affect point position accuracy.