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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
1. Introduction into the as-built-analysis
2. The high performance of the 3D-Laserscanning
3. The advantages of working with 3D-CAD models
- 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
As-built -analysis of Gate C6, Airport Frankfurt, Germany
The laser-scanner from Faro measures 120 000 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 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 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.