Abstract
Abstract. The use of Building Information Modeling (BIM) for existing buildings based on point clouds is increasing. Standardized geometric quality assessment of the BIMs is needed to make them more reliable and thus reusable for future users. First, available literature on the subject is studied. Next, an initial proposal for a standardized geometric quality assessment is presented. Finally, this method is tested and evaluated with a case study. The number of specifications on BIM relating to existing buildings is limited. The Levels of Accuracy (LOA) specification of the USIBD provides definitions and suggestions regarding geometric model accuracy, but lacks a standardized assessment method. A deviation analysis is found to be dependent on (1) the used mathematical model, (2) the density of the point clouds and (3) the order of comparison. Results of the analysis can be graphical and numerical. An analysis on macro (building) and micro (BIM object) scale is necessary. On macro scale, the complete model is compared to the original point cloud and vice versa to get an overview of the general model quality. The graphical results show occluded zones and non-modeled objects respectively. Colored point clouds are derived from this analysis and integrated in the BIM. On micro scale, the relevant surface parts are extracted per BIM object and compared to the complete point cloud. Occluded zones are extracted based on a maximum deviation. What remains is classified according to the LOA specification. The numerical results are integrated in the BIM with the use of object parameters.
Highlights
A Building Information Model (BIM) is a digital 3D object oriented database of a building
In order to differentiate between these multiple surveys, it is necessary to add some type of unique survey identifier to the quality assessment parameters of the Building Information Modeling (BIM) objects
A standardized method for geometric quality assessment of BIMs based on point clouds - as part of the scan-to-BIM process - will improve the reliability and usability of the model
Summary
A Building Information Model (BIM) is a digital 3D object oriented database of a building. One of the three typical challenges described in the above literature review article regarding BIM for existing buildings, is “the handling and modeling of uncertain data, objects and relations occurring in existing buildings in BIM” (Volk et al, 2014). We argue for more frequently executed geometric quality assessments of as-built and as-is BIMs. A more standardized framework around scan-to-BIM accuracy - including methods for deviation analysis and incorporation of the outputs in the BIM - is needed in order to make the final BIM more reliable and reusable by other stakeholders.
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