AS-BUILT-ANALYSIS THROUGH 3D- LASERSCANNING AND CAD-MODELING 1. Introduction into the as-built-analysis 2. The high performance of the 3D-Laserscanning 3. The advantages of working with 3D-CAD models

Introduction into the as-built-analysis Engineers and Architects must deal more and more with existing buildings nowadays. Eastern Europe follows the experience of the west, where it is difficult to find an empty place to build a new construction in the cities. The statistics show that the volume of reconstructions of residential buildings in Europe is as much as the volume of the new constructions.

Introduction into the as-built-analysis Before the planning of a reconstruction begins, the project team needs an exact as-built analysis of the existing building. Depending on the complexity of the reconstruction, this analysis can go deep in very small details and can include installations, machines and other specific elements of the building. Often, the old buildings have not plans at all. The plans have been lost, or partially exist but don’t correspond to the reality. Every building has its lifecycle. It was born, maintained, renovated and finally ruined when it gets old. The plans of the building are like man’s medical record. Every time, when a change in the building or in the installation is done, the planner should put a record in the plans.

Introduction into the as-built-analysis Unfortunately, in most of the cases in the practice, this is an exception, but not a rule. An input of good records enables the project team to take the right decision about how to plan a cost-effective and uncomplicated reconstruction. The use of wrong data during the planning stage is like a wrong diagnosis. It is followed by a chain of painful tasks during the reconstruction. Planning mistakes can be very expensive, especially when they cause delays of the whole reconstruction process. Before the planning of a reconstruction begins, the planning team have to make an as-built-analysis. There are different methods to measure a building: - In some simple cases it is enough to make a drawing by measuring some characteristic points manually using some simple measuring instruments. - In other cases the as-built-analysis is done using photogrametric methods. - Consider complex buildings, where a lot of objects have to be measured three-dimensionally, the positions of single points are captured with a tachymeter. - Using a 3D-laserscanner millions of points can be taken in a very short time

The high performance of the 3D- Laserscanning The traditional systems provide us with information about single points only. On the other hand, it is easy to understand, that huge number of points has to be used when dealing with complex buildings and facilities. This process could be very expensive and time consuming, if using traditional systems. The 3D camera and the laser- scanning technology enable us to enter 30 million measuring points within 4 minutes. This means, that for example an industrial hall with many thousands of square meters can be captured in several days only. Using the conventional methods of measurement it can take months to capture all the objects three- dimensionally.

The high performance of the 3D- Laserscanning As-built -analysis of Gate C6, Airport Frankfurt, Germany

The high performance of the 3D- Laserscanning The measured points form point-clouds, which are as big as the building itself. The resolution of the scanner is up to thousand times higher than the resolution of a commercial mega pixel camera. The 3D photographs are made from different positions in order to reduce the shadowed areas. Colour scans are also possible in a combination with a digital camera, which adds to the 3D pixels information about the colour. The laser-scanner from Faro measures points per second. It is an uncomplicated, highly-precise easuring method to create a detailed three- dimensional image of the urrounding objects. The measuring range of the Faro scanner LS880HE80 is 79m. Allaround pictures are taken in few minutes and contain millions of 3D measuring points. The 3D hotographs, the so called scans, can be taken from different positions inside and outside of the building.

The advantages of working with 3D- CAD models The users of scan data can make a part of the as-built-analysis directly in the scan, but in most of the cases the scans are not enough to start the planning of a reconstruction. The engineers and architects need realistic CAD drawings, which can be taken as a reference to their plans in their CAD systems. In most of the cases the as-built-analysis does not consist just of walls, slabs, windows and doors. The installations of the buildings are an important part of them, which have to be taken into consideration by the redesign. Using laser scans detailed 3D CAD drawings can be modeled. The existing 2D layouts can be compared with slices through the point-cloud in different levels in order to check whether they are built correct. In order to draw a complete 3D-CAD model of a building, a team of engineers and draftsmen make selectively modeling.