Experiences related to utilisation of laser scanning for engineering surveying tasks (verification of accuracy capabilities)

The presented results of investigation of accuracy point out that the laser scanning technology may be applied for such measurements where the highest accuracy of coordinates determination is not required. Performed tests also proved that in the course of utilisation of the laser scanner measurements various factors, which influence the accuracy of obtained results, should be considered. Specific characteristics of the output product of laser scanning (i.e. the cloud of points) are also very important. Though high density of the cloud occurs, the possibility to improve interpretation capabilities through utilisation of the intensity image (or digital photographs) and high accuracy of determination of co-ordinates of an individual point within that cloud, the accuracy of identification of particular points and lines within that object is limited. This results in the necessity to change the measurement methodology and to focus on detection of surfaces and automatic identification of shapes, instead of identification of individual points. In such approach to determination of the object's shape, many points are used, what allows for better identification of the object and to decrease the influence of incidental errors. A separate issue, which influences the accuracy of measurements performed by means of a laser scanner, is the possibility to eliminate instrumental errors in post-processing. It has been stated that utilisation of corrections due to non-perpendicularity of axes and corrections for distance measurements allows to increase the accuracy of co-ordinates measurements by approximately 10 - 15 %.