1. INTRODUCTION
This is the paragraph right after the heading 1, it should appear when user click on heading 1 in left pane (the heading pane)
1.1 PURPOSE OF THIS DOCUMENT
This NATSPEC BIMThe BIM object shall include properties that are organised so that they are easily viewed and retrieved, and consistently located within the BIM platform where possible Paper seeks to address some of the issues currently associated with Level of Development (LOD) in the AEC industry. These include:
- MisconceptionsThe BIM object shall include properties that are organised so that they are easily viewed and retrieved, and consistently located within the BIM platform where possible and misunderstandings about LOD.
- The value of LOD as a project management tool.
- A lack of clear guidance about applying LOD on projects.
- The layout and complexity of many LOD Tables overwhelms many practitioners and discourages them from investing the development time necessary to make them a useful management tool, or even making a start.
- The format of many LOD Tables obscures, rather than clarifies, important patterns and relationships, reducing their effectiveness for their intended use.
- Although there are a number of LOD Table templates available, there is currently no industry accepted standard. Practitioners are faced with different LOD Table formats from project to project, making their interpretation more difficult.
2. OVERVIEW OF LEVEL OF DEVELOPMENT (LOD)
2.1 MODEL DEVELOPMENT AND LOD
Level of Development is a conceptual framework that attempts to address the fact that model elements develop at different rates during the design process (See sidebar). LOD describes the relative development of individual model elements in their journey from conception to realisation. Locating an element on this evolutionary scale indicates how much it can be relied on for decision making purposes. LOD is a metric that allows project programmes and deliverables to be more clearly defined. As an industry standard, it aids communication and coordination between project stakeholders.
2.1.1 History of LOD
2.1.1.1 Name of object
The BIM object shall include a 'Name' property completed with a unique human readable alphanumeric name that begins with the product type.
Vico software first developed a metric, which they referred to as Level of Detail, for describing how definitive model elements were for the purposes of cost estimating. The American Institute of Architects (AIA) developed the concept further in AIA Document E202 – 2008 Building Information Modeling Protocol Exhibit. It includes this definition: “The Level(s) of Development (LOD) describes the level of completeness to which a Model Element is developed.” It describes the steps through which a model element can logically progress from the lowest level of conceptual approximation to the highest level of representational precision. The document defines five Levels of Development and assigns numerical notations from 100 – 500 to them. Each subsequent level builds on the previous level. The definition of LOD was amended in AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form to the following: “The Level of Development (LOD) describes the minimum dimensional, spatial, quantitative, qualitative, and other data included in a Model Element to support the Authorised Uses associated with such LOD.” Note the shift from a narrow Model Element-based definition to one linking LOD to Authorised Uses. Refer to 2.3.1 Authorised Uses.
2.1.1.2 Name of Object
The BIM object shall include a 'Name' property completed with a unique human readable alphanumeric name that begins with the product type.
Vico software first developed a metric, which they referred to as Level of Detail, for describing how definitive model elements were for the purposes of cost estimating. The American Institute of Architects (AIA) developed the concept further in AIA Document E202 – 2008 Building Information Modeling Protocol Exhibit. It includes this definition: “The Level(s) of Development (LOD) describes the level of completeness to which a Model Element is developed.” It describes the steps through which a model element can logically progress from the lowest level of conceptual approximation to the highest level of representational precision. The document defines five Levels of Development and assigns numerical notations from 100 – 500 to them. Each subsequent level builds on the previous level. The definition of LOD was amended in AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form to the following: “The Level of Development (LOD) describes the minimum dimensional, spatial, quantitative, qualitative, and other data included in a Model Element to support the Authorised Uses associated with such LOD.” Note the shift from a narrow Model Element-based definition to one linking LOD to Authorised Uses. Refer to 2.3.1 Authorised Uses.
2.1.2 LOD notations
The AIA LOD notations are comprised of numbers at intervals of 100, allowing the system’s users the flexibility to define intermediate LODs. Defining additional LODs can be crucial in some circumstances, particularly for contractual reasons, e.g. the handover of models from the design team to the construction team. The definitions of each LOD from LOD 100 – LOD 500, given in AIA Draft Document G202 – 2012, are summarised in Table 1. Note: Short descriptions are from AIA E202-2008
2.1.3 Aspects of LOD
The LOD concept encompasses a number of aspects of designed elements:
• Level of graphic detail/precision of modelling.
• Amount, quality and relevance of non-graphic information.
• Type of non-graphic information, e.g. embedded in model elements, linked to model elements, separate from (but cross referenced to) model elements. While all these aspects contribute to the concept of LOD, they do not define it - LOD is the sum value of them all. Essentially, when all of these aspects are taken into consideration, LOD represents the extent to which information about an element can be relied on for decision-making purposes at a particular point in time. This is the most crucial notion in the context of collaborative working arrangements.
2.1.4 Level of Development versus Level of Detail
There often appears to be a correlation between LOD and Level of (graphic) Detail because, as the design of elements become more resolved, they are usually defined more precisely geometrically and graphically. In fact, the increasing graphic detail of an element is often used to illustrate LOD (as in the LOD summary above). Unfortunately, this can confuse the two concepts. That they share the same acronym does not help either. As noted earlier, making assumptions about LOD based on appearance can lead to problems. Figure 1 illustrates how Level of Development and Level of Detail do not always coincide.
2.2 LOD TABLES – CHOREOGRAPHING MODEL DEVELOPMENT
Integral to the concept of LOD is model development (sometimes called progression) and collaboration. With so many model elements needing to be developed over time by different parties, how can the process be coordinated? AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form includes a Model Element Table for documenting thecollaborative development of models during a project using protocols defined in associated documents AIA Draft Document E203 – 2012 Building Information Modeling and Digital Data Exhibit and AIA Draft Document G201 – 2012 Project Digital Data Protocol Form. The Model Element Table can be used to document who is to be the Model Element Author (MEA) for each model element at each project phase, and to what LOD it must be developed. The intention of LOD Tables is to provide clarity and certainty about what is expected of everyone involved, so they can plan their work with confidence. Knowing the LOD of model elements at each stage will determine how much reliance the recipient will place on it, how much effort they will invest in resolving issues associated with it, and how much responsibility they will take for work based on it.
2.2.1 LOD Tables as a project management tool
LOD Tables can assist communication between project stakeholders and improve its management. They are often included in BIM Management Plans for the following purposes:
• As a common reference for stakeholders planning model development.
• For recording agreements made about model deliverables.
• For planning and coordinating project resources.
• For communicating project requirements to team members and organising their workflows.
• For monitoring progress against the project program. Responsibilities for managing the development and updating of the LOD Table should also be documented in the BIM Management Plan.
| Firstname | Lastname | Email |
|---|
| John |
Doe |
This email address is being protected from spambots. You need JavaScript enabled to view it. |
| Mary |
Moe |
This email address is being protected from spambots. You need JavaScript enabled to view it. |
| July |
Dooley |
This email address is being protected from spambots. You need JavaScript enabled to view it. |
2.2.2 LOD Table templates
The preparation of an LOD Table can be aided by using an existing template. Templates available include:
• AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form. Incorporates the well-recognised template or ‘Model Element Table’ on which most templates are based. Download from http://info.aia.org/aia/digitaldocuments.cfm.
• USACE Minimum Modeling Matrix (M3). An Excel based template incorporating the United States Army Corp of Engineers minimum modelling requirements for their projects. Its focus on two deliverables, the Design Model and the Record Model, reduces its complexity compared to many other templates. Built-in filters allow model content to be sorted by a number of criteria, simplifying the task of locating required information. Download from https://cadbim.usace.army.mil. See ‘Document Center’ > ‘BIM’. Note: You have to register or sign in for the documents to display. Click on ‘Sign in’ in the top right hand corner.
3. OVERVIEW OF LEVEL OF DEVELOPMENT (LOD)
3.1 MODEL DEVELOPMENT AND LOD
Level of Development is a conceptual framework that attempts to address the fact that model elements develop at different rates during the design process (See sidebar). LOD describes the relative development of individual model elements in their journey from conception to realisation. Locating an element on this evolutionary scale indicates how much it can be relied on for decision making purposes. LOD is a metric that allows project programmes and deliverables to be more clearly defined. As an industry standard, it aids communication and coordination between project stakeholders.
3.1.1 History of LOD
Vico software first developed a metric, which they referred to as Level of Detail, for describing how definitive model elements were for the purposes of cost estimating. The American Institute of Architects (AIA) developed the concept further in AIA Document E202 – 2008 Building Information Modeling Protocol Exhibit. It includes this definition: “The Level(s) of Development (LOD) describes the level of completeness to which a Model Element is developed.” It describes the steps through which a model element can logically progress from the lowest level of conceptual approximation to the highest level of representational precision. The document defines five Levels of Development and assigns numerical notations from 100 – 500 to them. Each subsequent level builds on the previous level. The definition of LOD was amended in AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form to the following: “The Level of Development (LOD) describes the minimum dimensional, spatial, quantitative, qualitative, and other data included in a Model Element to support the Authorised Uses associated with such LOD.” Note the shift from a narrow Model Element-based definition to one linking LOD to Authorised Uses. Refer to 2.3.1 Authorised Uses.
3.1.2 LOD notations
The AIA LOD notations are comprised of numbers at intervals of 100, allowing the system’s users the flexibility to define intermediate LODs. Defining additional LODs can be crucial in some circumstances, particularly for contractual reasons, e.g. the handover of models from the design team to the construction team. The definitions of each LOD from LOD 100 – LOD 500, given in AIA Draft Document G202 – 2012, are summarised in Table 1. Note: Short descriptions are from AIA E202-2008
3.1.3 Aspects of LOD
The LOD concept encompasses a number of aspects of designed elements:
• Level of graphic detail/precision of modelling.
• Amount, quality and relevance of non-graphic information.
• Type of non-graphic information, e.g. embedded in model elements, linked to model elements, separate from (but cross referenced to) model elements. While all these aspects contribute to the concept of LOD, they do not define it - LOD is the sum value of them all. Essentially, when all of these aspects are taken into consideration, LOD represents the extent to which information about an element can be relied on for decision-making purposes at a particular point in time. This is the most crucial notion in the context of collaborative working arrangements.
3.1.4 Level of Development versus Level of Detail
There often appears to be a correlation between LOD and Level of (graphic) Detail because, as the design of elements become more resolved, they are usually defined more precisely geometrically and graphically. In fact, the increasing graphic detail of an element is often used to illustrate LOD (as in the LOD summary above). Unfortunately, this can confuse the two concepts. That they share the same acronym does not help either. As noted earlier, making assumptions about LOD based on appearance can lead to problems. Figure 1 illustrates how Level of Development and Level of Detail do not always coincide.
3.2 LOD TABLES – CHOREOGRAPHING MODEL DEVELOPMENT
Integral to the concept of LOD is model development (sometimes called progression) and collaboration. With so many model elements needing to be developed over time by different parties, how can the process be coordinated? AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form includes a Model Element Table for documenting thecollaborative development of models during a project using protocols defined in associated documents AIA Draft Document E203 – 2012 Building Information Modeling and Digital Data Exhibit and AIA Draft Document G201 – 2012 Project Digital Data Protocol Form. The Model Element Table can be used to document who is to be the Model Element Author (MEA) for each model element at each project phase, and to what LOD it must be developed. The intention of LOD Tables is to provide clarity and certainty about what is expected of everyone involved, so they can plan their work with confidence. Knowing the LOD of model elements at each stage will determine how much reliance the recipient will place on it, how much effort they will invest in resolving issues associated with it, and how much responsibility they will take for work based on it.
3.2.1 LOD Tables as a project management tool
LOD Tables can assist communication between project stakeholders and improve its management. They are often included in BIM Management Plans for the following purposes:
• As a common reference for stakeholders planning model development.
• For recording agreements made about model deliverables.
• For planning and coordinating project resources.
• For communicating project requirements to team members and organising their workflows.
• For monitoring progress against the project program. Responsibilities for managing the development and updating of the LOD Table should also be documented in the BIM Management Plan.
3.2.2 LOD Table templates
The preparation of an LOD Table can be aided by using an existing template. Templates available include:
• AIA Draft Document G202 – 2012 Building Information Modeling Protocol Form. Incorporates the well-recognised template or ‘Model Element Table’ on which most templates are based. Download from http://info.aia.org/aia/digitaldocuments.cfm.
• USACE Minimum Modeling Matrix (M3). An Excel based template incorporating the United States Army Corp of Engineers minimum modelling requirements for their projects. Its focus on two deliverables, the Design Model and the Record Model, reduces its complexity compared to many other templates. Built-in filters allow model content to be sorted by a number of criteria, simplifying the task of locating required information. Download from https://cadbim.usace.army.mil. See ‘Document Center’ > ‘BIM’. Note: You have to register or sign in for the documents to display. Click on ‘Sign in’ in the top right hand corner.
