Measurement Uncertainty

BIM 2Building Information Modeling (BIM) can be defined as the generation and management of digital models of large structures, such as buildings and other infrastructures, throughout their sometimes decades-long lifecycle. Lidar has become a popular tool to document changes in the geometry of a structure during its lifecycle.

For large structures many scans (lidar depth maps) must be combined to achieve complete coverage; however, combining the scans required to model the geometry of large, and sometimes complex, features may introduce geometric distortion as a result of cumulative alignment error. Moreover, changes in scanning technologies and methodologies can increase the deviation between the geometry of digital representations of the original structure and digital models generated later in the structure’s lifecycle. The use of best practices makes it possible to create digital models generated in accordance with accepted standards using measurements with quantified uncertainty values. Best practices make it possible to distinguish between variation due to structural changes and variation due to measurement uncertainty due to the scanning technology and methodologies employed.

For our test study, we generated a digital model of a 130 m x 55 m x 20 m stone-and-brick building over a steel structure using a combination of lidar systems, laser trackers, spherical artifacts, and contrast targets. We built a reference model with an expanded uncertainty (k=3) of 33.63 mm, a one-sigma surface RMS of approximately 2.36 mm, and an average spatial resolution of about 20 mm. By including measurement uncertainty in our digital model we will be able to monitor the structure for decades to detect changes in physical geometry, such as changes due to local seismic activity or structural degradation.

(Thanks to David MacKinnon for submitting this project showcase. If you would like to showcase a project on the Lidar News website please contact me at editor@lidarnews.com.)

David MacKinnon, Ph.D., P.Eng.,

Research Officer / Agent de recherche

Mechanical Metrology / Métrologie mécanique

Measurement Science and Standards / Science des mesures et étalons

National Research Council of Canada / Conseil national de recherches Canada

 

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2 Responses to Measurement Uncertainty

  1. David MacKinnon says:

    The paper related to this article can be found at http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?reload=true&arnumber=7182726&punumber%3D7035242%26filter%3DAND(p_IS_Number%3A7182697)%26pageNumber%3D2

    The primary author was Marc-Antoine Drouin of NRC. Co-authors were Jean-Angelo Beraldin, Luc Cournoyer, myself, Louis Borgeat, Guy Godin, and Jonathan Fournier.

  2. Well there is a huge difference to get a 3D model of something and a construct plans detail for something.

    It is possible to make it , but the Laser Scanns must be in Very High resolution and close capture. Certainly it depends on the grade of accuracy of a intended geometrical document. You can of course scan a building. But if you need to build a window frame i.e. you can´t intend to get accured constructing draws.

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