Positionering av markörer för luftrörelser : handhållen längdmätare kontra laserskanning
Abstract (Summary)The state of air (temperature and humidity) and movements in larger premises can be measured by a climate measuring system. In order to simulate air humidity, temperature, speed and direction in 3D the sensors in the climate measuring system needs to be positioned. In this study, two methods that can be used for positioning of objects are compared and evaluated. The first one is simple and uses a hand-held distance meter. The objects position are calculated by triangulation of three measured distances to points with known coordinates. The second method uses a terrestrial laser scanner and the result of this method will be considered as correct and constitute the study reference.The purpose of the study is to examine whether it with the simple method is possible to achieve centimetre accuracy when positioning objects and determine what marker size that is appropriate to use. The study should also include the development of a software to manage measured data and perform the position calculations for the simple method.Five known points were surveyed with a Leica TPS1200 total station. 16 spherical markers with the diameters from 20 to 50 mm were assembled in 4 marker groups and placed on stands. These markers were scanned with a Leica HDS3000 laser scanner and markers point cloud was model to obtain positions. All markers were then surveyed from the known points with a distance meter Leica Disto Plus. The distances from the known points to each marker were stored in the software DistoPos where the makers positions also were calculated.The two methods result were compared by calculating the simple method radial accuracy with the results of the laser scanning as a reference. The best accuracy was reached when the simple method positions were calculated in terms of the distance to the known points. When the three shortest distances were used for positioning the unaccuracy was divide into halves. This is mainly because of the geometry of the known points included in calculations was changed to the better. This underlines the importance of good geometry of the known points included in the calculations. The accuracy of individual markers ranged between 3 and 36 mm. The result shows that it will be difficult to achieve centimetre accuracy with the methods prerequisites.The position calculations for the simple method would be further enhanced by the inclusion of some kind of adjustment, and procedures to identify and correct gross errors.
School:Högskolan i Gävle
Source Type:Master's Thesis
Date of Publication:10/22/2008