First Experiences with the Trimble Gx Scanner

Trimble introduced a new generation of terrestrial laserscanners (TLS) in October 2005. It was on the one side a further development of the Mensi GS200 series and on the other hand presented as “the 3D scanner that thinks like a surveyor”. The Trimble GX was tested regarding its precision, accuracy, attitude of reflection at different coloured surfaces and materials. A specific test field was used for the tasks. Furthermore the authors report about first projects in the fields of architectural and topographical applications, as for example the Documentation of the „Pontonniers International High School“ in Strasbourg, were the levelling of the laserscanner and the direct georeferencing of the point clouds with the new workflow has been tested. Specifically very interesting was the testing of the traditional total station workflow which is up to now uncommon for TLS systems: the scanner can be set up over known points measured with flat targets to provide a direct relationship to existing ground control. The workflow available for the Trimble GX laserscanner is close to the standard fieldwork methods where a network of control points measured by GPS or total stations are now also used as reference stations for the laserscanner. Measurements between stations commonly referred to as traverse measurements, provide an instant relationship between multiple stations and allow the user to view homogenous data in the field without additional post processing. The quality and extent of the survey data can thus be verified in the field. A comparison of standard field methods and geodetic adjustments to the corresponding 3D scanner survey workflow are presented, based on experiences with both Pointscape and Pocketscape software.