as-built-analysis through 3d-laserscanning and cad

4TH INTERNATIONAL CONFERENCE
RECENT PROBLEMS IN GEODESY AND RELATED FIELDS WITH
INTERNATIONAL IMPORTANCE
February 28 - March 2, 2007, Inter Expo Centre, Sofia, Bulgaria
AS-BUILT-ANALYSIS THROUGH 3D-LASERSCANNING AND
CAD-MODELING
STOYAN TODOROV (DE)
1. Introduction into the as-built-analysis
2. The high performance of the 3D-Laserscanning (+ a short film)
3 The advantages of working with 3D-CAD models
4 Case studies
4.1 As-built -analysis of Gate C6, Airport Frankfurt, Germany
4.2 As-built – analysis of Maritza East II Power plant, Bulgaria
1. 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.
Before the planning of a reconstruction begins, the project teem 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 planer should
put a record in the plans. 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. ItA 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 teem 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 threedimensionally, 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
* A short film about the 3D-Laserscanner from Faro. It can be seen on: www.iqvolution.ws
3. 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 laser-scanner from Faro measures 120 000 points per second. It is an uncomplicated, highlyprecise measuring method to create a detailed three-dimensional image of the surrounding objects.
The measuring range of the Faro scanner LS880HE80 is 79m. All-around pictures are taken in few
minutes and contain millions of 3D measuring points. The 3D photographs, 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 raw scan data is just a point-cloud without information about orientation. In order to put it into
a certain coordinate system and to connect it with other scans, we need to build a system of
reference points before the scanning begins:
•
If we want to build a local coordinate system in order to co-ordinate information between
neighbour scans (to register the scans), we can use reference spheres used as common
objects which can be seen from several neighbour scans. Minimum 3 points should be
recognised from each scan in order to place it properly into the coordinate system. In
iQvolution Bulgaria Ltd., we take minimum 4 points in order to secure the quality of the
scan registration. By the local registration it is important to find out a proper configuration
of the scans and the reference points. A particular scan should be able to see all of the
reference points used for a registration of that scan. The rest of the neighbour scans are coordinated to a particular scan, by using common reference spheres. The Faro scanner uses
spheres for the registration, because a sphere looks always in the same way from every
single scanning position, and it has a defined centre point, which can be calculated
automatically from the software.
•
If the project consists of many scans without a possibility to connect them through a masterscan or if the point-cloud must be positioned in the global coordinate system, then should be
created a net of reference points. The coordinates of every single reference point must be
measured. In order to fix the spheres to the walls, pillars and so on, are used special bolts.
The same net of reference points can be used again, if rescanning is necessary after a certain
period of time. Using the same fixed bolts, surveyors put prisms on the place of the spheres
and measure the coordinates of the reference points. The prisms have an adaptor which has
the same length, as the radius of the sphere. Every single point has a unique number which
is represented as a label next to it.
On one hand, there are the coordinates of the reference points, measured by a tachymeter.
On the other hand there are the centre points of the spheres which are automatically
recognised in the raw scan data. The software Faro Scene transforms the scans; every centre
point of a sphere takes the coordinates of the point with the same name. The operator
decides how many points to take in order to put the scan in the right position. The minimum
number of points is 3. The registration of the scans puts them in a common coordinate
system. Using the global coordinates the point-cloud fits exactly on the plan of the building.
Provided with the registered point-clouds, users can start with the as-built-analysis. The
Laserscanning has many different fields of application: architecture, planning of installations and
facilities, automatisation and factory planning, civil engineering (tunnels etc.), archaeology and
documentation of cultural monuments, mechanical design of big objects like ships, etc. Depending
on the field of application users can take different software solutions:
•
ScanManager is a fast, efficient and easy to use tool for management of 3D Laser scan data.
Using this software, users can generate horizontal and vertical slices through the pointclouds at any level by using many hundreds of scans at once. The program draws signs of
the scans and the reference points in the slice pictures. Selecting a certain scan, the user can
open the scan picture and can navigate within it. The software is capable to recognize
objects in the point-cloud like cylinders (pipes), spheres, planes and middle points. The user
can make measurements between selected objects, draw objects and attach information to
them. The user can dynamically see the 3D coordinates of every pointed out scan-pixel. For
more information look at the homepage: www.3d-scanline.com > Downloads > Scan
Manager
•
Faro Scene is software for viewing, administration and working on, of extensive scan points
from high resolution 3D laser scanners like the scanner from the company Faro. This tool
allows to the user to manipulate raw 3D scan points and acquire by analysis functions initial
point-cloud data comprehension. Through data analysis and manipulation, scan points may
be prepared for export into the user‘s CAD system.
In the 3D view both point-clouds and objects are displayed. The point of view is arbitrarily
selectable, the user can freely move in the area. The importing of VRML models makes it
possible to analyze models and to recognize collisions and deviations. This analysis is
achieved quickly and intuitively, directly in the
3D point-cloud.
Faro Scene makes the acquisition of information possible directly from 3D scan points.
Besides measuring distances between objects, surface areas and volumes may be determined
by the user. Special functions also allow the user to examine the evenness of floors or walls
and display the results in a colour coded scale. For the reduction and simplification of pointcloud data the user may generate scan based objects. Objects such as planes for floor and
walls facilitate the exporting of data into the user‘s CAD system. For more information, look
at the homepage: www.faro.com > Products > Laser scanner LS > Software
2. 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. By reconstructions of factory buildings, for example, the installations
can take even a dominating role of importance by the as-built-analysis. By refurnishing of
production halls the planers must take into consideration many existing elements like steel
constructions or machines. The technology of 3D-Laserscanning and CAD-Modelling enables the
planning team to make virtual models in order to check whether the new equipment will fit to the
hall.
Using laser scans detailed 3D CAD drawings can be modelled. 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 modelling.
•
•
•
The building’s components can be drawn in 3D using standard software for architectural
planning. The point-cloud is imported through *xyz, *dxf and read in *dwg or *dgn formats.
The elements of the building are separated in different layers and can be associated with
various kind of additional information. In most of the cases, it is required that the drawings
should be done according to the CAD standards of the planer or the building owner.
The installations are drawn in the same way like the architectural elements through selecting
the single parts in the scan and importing them in the CAD program. For example, to get a
realistic CAD model of piping, electro installations or ventilation the users can use the
software “Pit-Cup” or “Tricad”. For more information about this software, please look at the
homepage: www.iqvolution.ws > pit.cup / iTandfactory.
When the CAD model is completed, the drawings are put together in a virtual reality model.
Using the software Navis Works, users can “take a virtual tour” through the building on the
computer screen and analyse the collision risks in the building. The software offers the
possibility to make visualisations of the project and to plan in 4D, showing the sequence of
the stages of the reconstruction works. For more information about these software, please
look at the homepage: www.iqvolution.ws > Navis Works
The object oriented 3D-CAD models, generated on the basis of the scan data, are an important
requirement for the improvement of all the processes during the construction planning, and
contribute to reduction of planning mistakes. Since, the modelling is time-consuming, it is often
more effective to do the measurements in the scan, to have reliable plans and to test the collision
risks in the virtual reality model. Thus, mistakes can be recognised already at the planning stage and
eliminated cost-effectively, also delays for the start of production can be avoided.
4 Case studies
In the last chapter will be represented two projects of “iQvolution Bulgaria Ltd”.
4.1 As-built -analysis of Gate C6, Airport Frankfurt, Germany
Our company was asked to make as-built-analysis of one of the old gates at Germany’s biggest
airport in Frankfurt and to draw detailed models of the building and of the installations belonging to
it. The Project started in March 2006. We made 221 scans to capture the 3 levels of the airport gate.
The scanning works and the survey of 288 reference points have been done from a team of 4 people
and took 2 weeks time. During the first week we made the scanning and the survey works of the
basement which was very compact installed. During the second week we scanned and made the
survey at the ground floor and the first floor. There are placed the offices of different air
companies, passenger lounges and corridors. The airport staff gave to us the coordinates of several
existing reference points in order to connect our net to the local net. The gate was in use 18 hours a
day and we were allowed to scan the passenger lounges at night only. Because of the security
precautions, we had to pass through the border control, every time we went up on the first floor.
A teem of 5 engineers and drafters worked 9 weeks to model the 3D-CAD plans of the airport
building and its installations. The CAD data must have been organised according to the standards of
the company who owns and manages the airport. The required software was Microstation,
Speedikon M for the building, and Tricad MS for the installations.
During the long years of exploitation of the airport facilities, there were made plenty of changes.
Some installations were renovated but there were no existing records in the documentation. In order
to start to plan a complete renovation of the gate, the planning team needed exact CAD plans in 3D.
4.2 Laserscanning at Maritsa East II Power plant, Bulgaria
In 2004 Toshiba Corporation asked our mother company iQvolution AG, Germany, to scan the
turbine hall of Maritsa East II Power plant in Bulgaria. The Japan Company had the task to
reconstruct 3 turbine units of the power plant and 4 generators.
During the 25 years of work the facilities have been reconstructed many times. The quality of the
existing documentation was insufficient to start to plan the exchange of the old Russian turbines and
generators with new equipment from Toshiba. There are plenty of installations which connect the
units with the other parts of the power plant like the boiler hall or the cooling towers. By such
complex facilities it is almost impossible without such a detailed as-built analysis to assure, that
every old pipe will be connected properly to the new turbine.
On the first day of the project a team of 11 engineers from Japan appointed us which parts of the
turbine hall are important for the planning. Placing the scan positions, we decided together about
the number of 356 Scans, which were necessary to picture the turbine hall. A team of Bulgarian
surveyors measured 610 reference points and connected them with the local coordinate system of
the plant. In order to check the dimensions of the fundaments, the Japanese civil engineer asked us
to make 2D slices through the whole point cloud of the hall on 9 different heights. The turbine hall
has 5 levels. Every level was documented through 2 slices - one above the floor and another under
the ceiling. In this way planers could find out the dimensions and the exact positions of the
complicated installations, which go trough the different levels.
Taking the 3D data from the laser scanner on 5 DVDs to Japan, the planers saved a lot of money for
travelling over the ocean. The realistic 3D pictures and the possibility to take measurements in the
scan made possible to use methods of virtual engineering. Using the Software Navis Works the
Japanese constructors could plan the transportation path of the new turbines in order to lay them
properly on the old fundaments without collisions with the surroundings.
Dipl. Eng.(TU Munich), M.Arch. Stoyan Todorov
iQvolution Bulgaria Ltd.
P.O.Box 266, BG-6000 Stara Zagora, Industrialna Str. 1
Tel. +359 (0) 42 627299, Fax. +359 (0) 42 643954
[email protected]
www.iqvolution.ws