LOR = LoA + LoQ

 

[1]

LOR, referred to as model reliability (reliability level), consists of LoA - geomentric accuracy and LoQ - information reliability. The term was created to standardize the as-built documentation, i.e. the level of handover of the building for use, and is an important milestone in the entire life cycle of the building (the Management Stage). As examples and current research on the use of BIM for the renovation and maintenance of buildings show, there are still many unknowns in this regard. If the BIM methodology is problematic in terms of practical application to older buildings, the same problem will exist with the as-built BIM model and the BIM building management model. In order to present the concepts of LoA, LoQ and LOR, we present below the most important fragments of the scientific article: Reliability in Scope in HBIM Architectural Modeling, by P. Maiezza:

Document translation

The article deals with the issues of transparency and reliability in modeling architectural heritage in the BIM environment. In particular, based on the survey and modeling of some case studies, the aim of the article is to define a reference standard for the reliability declaration of HBIM as-built models.

The as-built model cannot be treated as a simple three-dimensional form of the studied reality, but as a process of analysis, synthesis and communication of architectural complexity, including, in addition to geometric and dimensional aspects, also the historical, aesthetic and architectural features of the building. Consequently, the issues of transparency and reliability of digital visualization are, as for archeology, an issue of paramount importance in modeling cultural heritage. The growing interest of scholars in applying building information modeling (BIM) to historic buildings has renewed as-built reliability issues related not only to the relationship between the model and the measure, but also to information such as constructive technologies. Based on the review and modeling of some case studies, the aim of the article is to define a reference standard for the reliability declaration of HBIM as-built models, which takes into account both geometric and informational aspects.

The as-built model should therefore not be treated as a simple three-dimensional form of the studied reality, but as a process of analysis, synthesis and communication of architectural complexity, including, apart from geometric and dimensional aspects, also the historical, aesthetic and architectural features of the artifact. Consequently, the topic of digital visualization transparency is, as for archeology, a top priority. The importance of the issues of transparency and reliability in the modeling of architectural heritage has led to interesting studies, mainly focused on the procedures for declaring the level of reliability of representation depending on the type of source used.

Regarding geometric restitution, four levels of reconstruction have been defined: 1) based on geodetic data; 2) based on images in a conical or cylindrical projection; 3) based on pseudo-perspective images, pseudoaxonometry or sketches; 4) without iconographic support or survey data. Apollonio et al. (2013) deal with the problem of "uncertainty" of 3D models of buildings that no longer exist or have never been realized.

Bianchini et al. (2018) introduce the Reliability Level (LOR) as a new attribute for handling digital objects. This parameter, ranging from 0 to 10, is the average of various factors that can affect both the geometrical reliability of the element and the ontological compatibility between the virtual and the real object. In order to more quickly declare the reliability of the model, the numerical LOR scale is further translated into a simplified chromatic scale with only three levels of reliability (high, medium and low). Finally, Brumana et al. (2018) define modeling protocols, called "Grades of Generation" (GoGs), aimed at obtaining the Geometry Level - in relation to the LoD split in the LOG and LOI

Due to the dual nature of BIM (model and database) and the division of the "Object development level" (LoD) in the LOG (Object development level - GEOMETRIC ATTRIBUTES) and LOI (Object development level - INFORMATION ATTRIBUTES), made in the UNI 11337: 2017 standard for digital objects, a double level of reliability is proposed:

• Accuracy level (LoA) relating to geometric accuracy, measured as deviation;
• Quality level (LoQ), related to the information content related to a single item.

Together, these two levels measure the reliability of an architectural element model (reliability level - LoR). BIM is not intended for paradata, however its double value of graphical representation on the one hand and informative content on the other can be used to record and transmit data, information and interpretative choices that underpin modeling. In particular, the ability to store and manage the large amount of heterogeneous data offered by BIM can be used to connect various elements of the model with documents (images, surveys, historical photos, etc.)

LoA

• Low level on 70% of the surface of the model with a deviation greater than 50 mm;
• Average level when 70% of the model has a variation value of 20 mm to 50 mm and 30% with a variation greater than 50 m;
• High level when 70% of the model has a variation of less than 20mm and 30% of a variation of less than 50mm;

LoQ

• Low level of reliability for the exclusive use of indirect sources, ie from other sources that only allow the reconstructive hypothesis of the object;
• The average level of reliability of the use of primary sources (directly related to the analyzed architectural element) is not exhaustive, as it leaves open doubts and uncertainties;
• High level of reliability in the case of modeling based on the use of direct sources, which allow full knowledge of the architectural element;

Sources:

[1] pixabay.com; author: Thomas Breher

[2] Scope Reliability in HBIM Architectural Modeling - P. Maiezza - 1 Civil, Structural Architectural and Environmental Engineering Department, L'Aquila University, Italy 2019 - https://www.google.com/url?q=https% 3A% 2F% 2Fwww.researchgate.net% 2Fpublication% 2F330769741_AS-BUILT_RELIABILITY_IN_ARCHITECTURAL_HBIM_MODELING & sa = D & sntz = 1 & usg = AFQjCNFyyvV-NSqwuZBa6QRqLDAOSY