AS-BUILT MODEL OF THE CENTRAL BANK OF NIGERIA (CBN) CENTRE OF EXCELLENCE BUILDING UNIVERSITY OF NIGERIA ENUGU CAMPUS USING LEICA HDS SCANSTATION 2
ABSTRACT
Laser scanning technology has grown to become a useful surveying tool in many industries in the last decade. Laser scanning is now used in many areas such as surveying, engineering, mining, architecture, archaeology, crime investigation and control, agriculture, historic documentation, industrial pipe plant surveys etc. A laser scanner is a powerful surveying tool that is able to survey and record about 50,000 (fifty thousand) points in a second. This gives today’s surveyors the option of recording vast amounts of field data in a fast and accurate way. In recent times the study of engineering structures has been on the rise for several uses, varying from as-built survey, deformation studies, improved planning for renovations to more accurate modeling of a building, control of the verticality of a high rise building, disaster assessment and management, etc. As-built drawings are drawings that represent the actual built structure. Not as it was designed, but as it actually is today (i.e. the day of measurement). People always make changes to their designs during the construction process and these changes almost never make it back to a set of revised plans because it was made in the field, there’s no reason to update the plans, whose sole purpose is to tell the builder what to build. Also, a building of any vintage may have had additional projects that made alterations to its original form, that may have affected everything from interior finishes to the core structural system of the building (and this includes brand new buildings too). More often than not, these projects are executed without permits, plans, and in the worst cases, without the guidance of someone who knows what they are doing. These observations point to the need for methods to create as-built models. The creation of an as-built model involves measuring the geometry and appearance of an existing facility to obtain a collection of spatial data and transforming those measurements into a high-level, semantically rich representation (i.e. As-built Model). This study will be determining the as-built survey of the Centre of Excellence Building in tprhe University of Nigeria, Enugu Campus and establish deformation monitoring framework for the building. Although as-built building information is useful, the current process for capturing, retrieving, and modeling, such information requires a lot of manual, time-consuming work. This labour intensive and time-consuming nature increases the cost of using as-built building information in practice. In order to address these issues, this project investigates the potentials of using High Definition Surveying (HDS) terrestrial laser scanning equipment named Leica ScanStation 2 to generate millions of point cloud spatial data for automatically capturing, retrieving, and modeling the exterior as-built building geometry and features in a very short time. The point cloud was georeferenced to a real world coordinate system established around the building by static GPS observation. Although this study was supposed to establish deformation monitoring framework for the building, the massive construction work still going on at the time of this project execution, will disturbed any monitoring point established on the structure hence this study will only demonstrate the possibility of using Leica ScanStation 2 for deformation monitoring using seven points fixed on the building for deformation monitoring. The results from the scanning sessions were analysed with Cyclone software to produce a 3D view of point clouds and a 3D view of as-built model of the structure exported to AutoCAD format. This result is useful in capturing construction deviations from construction documents, resource for future maintenance and planning and provides a snapshot of existing design.
Keywords: terrestrial laser scanning, as-built, georeferencing