In this guest post, Marzia Bolpagni (PhD Candidate, Politecnico di Milano, Italy) provides a comprehensive review of the 'LOD' term and its many nuances from across the world. I’m sure you’ll find her insights, comparative tables and detailed charts very informative:
Introduction
All practitioner who use Building Information Modelling tools and workflows in their daily practice must have already faced the ‘information exchange dilemma’. That is, to effectively deliver a project, it is first essential to define what information is needed, from whom, and at what level of detail. To meet this challenge, several international specifications have been developed to address the definition of modelled objects and information embedded within them – these include: Model Progression Specification (MPS), Model Development Specification (MDP), Level of Development, and Level of Detail. Usually, these specifications are included within a BIM Execution Plan (BEP) or a similar document. However, much confusion still surrounds these concepts due to the large number of acronyms and definitions across countries and sometimes within the same market. Thus, this post will focus on clarifying the principles, surveying historical data, differentiating between different specifications, and reflecting upon a possible future scenario.
History of ‘LOD’
In 2004, Vico Software (now part of Trimble) introduced the Model Progression Specification (MPS) concept to facilitate the management of information within BIModels. The ‘LOD' acronym was thus used for the first time to indicate ‘Level of Detail’ and to establish the progressive reliability of information over a period of time. In 2008, a similar concept was adopted by the American Institute of Architects (AIA), California Council’s Integrated Project Delivery (IPD) Task Force, and later by the AIA National Documents Committee. The AIA introduced five ‘Levels of Development’ (LOD100-LOD500) in the E202™–2008. Building Information Modeling Protocol Exhibit, which was updated in 2013. Also in 2013, the BIMForum published the Level of Development Specification based on the AIA protocols. These documents then became the point of reference of several BIM Guidelines and documents in a number of countries – including Australia, Canada, Singapore, China, Taiwan, Germany and France. Other countries developed their own variant specification. For example, in New Zealand, the LOD specification follows the AIA (2013) but defines ‘Level of Development’ (LOD) as a sum of four different aspects: ‘Level of detail’ (LOd), ‘Level of accuracy’ (LOa), ‘Level of information’ (LOi) and ‘Level of coordination’ (LOc).
In 2007, Denmark developed a different classification system based on seven ‘Information Levels’ (0-6) covering geometric and non-geometric data within virtual building elements that different parties rely upon. This concept was then incorporated into the Australian CRC National BIM Guidelines document (2009) and the ‘Nederlandse BIM informatieniveaus’ (2014), although the US Levels of Development (LOD100-LOD500) were the dominant system used in both countries.
Following that, the Hong Kong BIM Project Specification (2011) incorporated several tables for defining the minimum ‘Level of Detail’ required with models but without providing a classification.
Figure 1: The History of ‘LOD’ (Updated July 22, 2016 - Full-size Image)
In 2009 the AEC(UK) released a BIM Protocol introducing a Model Development Methodology incorporating the Level of Detail/Grade within a classification dedicated purely to geometric aspects (G0-G3). In 2012, the same concept was adopted in Canada by AEC(CAN). However, in 2014, the second version of the BIM Protocol now only refers to the BIMForum LOD Specification released in 2013. In the UK, PAS1192-2, was then published in 2013 and introduced the ‘Level of Definition’, a new classification system with seven levels (1-7) representing both a ‘Level of Model Detail’ (LOD) (for graphic content) and ‘Level of Model Information’ (LOI) (for non-graphic content). This concept was later incorporated, in 2015, into both the NBS BIM Toolkit and the AEC(UK) BIM Technology Protocol, while the CIC BIM Protocol (2013) continues to refer only to Levels of Detail. The UK approach has influenced the last version of the BIMForum LOD Specification (2015) which for the first time includes both Element Geometry and Associated Attribute Information. A new version will be available by July 2016 for public comments.
Other LoXs
Another classification deals with the Level of Accuracy (LOA) to represent and document existing conditions. The USIBD guideline (2016) uses different levels (LOA10-LOA50) and incorporates the validation process.
Finally, CityGML has developed five Levels of Detail (LOD0-LOD4) to define geometric details and semantic precision to link BIM with Geographic Information System (GIS) data.
Figure 2: ‘LoX’ relations and evolution (Updated July 22, 2016 - Full-size Image)
Conceptual Differentiation
The above variations of the same concept have – understandably – caused a large degree of confusion. Below are a few examples:
- The original ‘Level of Detail’ index was intended to measure the reliability of both geometric and non-geometric data, it now focuses more on the geometric attributes;
- The same ‘LOD’ acronym is interchangeable used for both Level of Detail and Level of Development;
- Identical concepts are occasionally referred using different terms (e.g. ‘Level of Information’ and ‘Associate Attribute Information’);
- The Level of Development – while intended to be associated with Model Components – it is sometimes mistakenly associated with whole BIModels; and
- Many BIM documents that these classifications are based on are now out of date.
Comparisons
The below two tables summarize the many different classification systems, within the main BIM documents, intended to specify the level of detail, development or information embedded within Model Components.
Table 1: Comparison of the intended coverage of LoX systems (Updated July 22, 2016 - Full-size Image)
Several classifications (included in Table 2) are already established. However, it is important to underline that – while many share the same name/acronym – they do not necessarily carry the same connotations. For this reason, there is not a perfect coincidence between levels of different classifications and some of them are not well defined as recently discussed by fellow researcher Brian Renehan. In addition, US classifications tend to mainly cover the design and construction phases and focus to a lesser degree on the operation, management and maintenance phase.
Table 2: Comparison of classification systems within different LoX systems (Updated July 22, 2016 - Full-size Image)
Reflections
To date, the many and increasing LoX concepts have been associated with the incremental progression of information definition within models. However, there are now voices who question whether these types of classification systems accurately represent reality. For example, in order to represent the iterative workflows within the design phase, Drobnik and Riegas (2015) suggest the introduction of Level of Development zero (LOD 0) as well as a negative one (LOD -100).
Also, there has been very little attention given to the link between LoX systems and Model uses as applicable in practice (even if some definitions mention ‘Authorized Uses’). In my opinion, for a LoX system to be applied more intuitively, it needs to be linked (i.e. change according to) targeted Model Uses at each project stage/phase.
Future Work
An important part of the BIM Processes that is yet to attract ample attention is Verification and Validation. The manual, automatic and semi-automatic compliance checking of information requirements within BIModels is still to be adequately resolved. Current approaches to Model Validation focus on static entities rather than on performing dynamic validation. It is therefore important that future research takes into account – not only the discrete Level of Detail (dLOD) but – the continuous LOD (cLOD), the continuous Level of Information (cLOI), and link both to specific Model Uses as applicable at each project phase/stage.
Another important aspect to address is how to apply LoX systems to existing buildings, as most classifications tend to focus on new construction.
Based on the above, and in collaboration with a number of colleagues, I will be investing additional efforts in trying to resolve some of the issues identified above. I therefore invite all BIM researchers and practitioners to do the same.
More Information
The study is part of an ongoing research effort conduced in collaboration with Prof Angelo Luigi Camillo Ciribini (@Ciribini) of University of Brescia (Italy). To review the peer-reviewed paper upon which this post is based, please download ‘The Information Modeling and the Progression of Data-Driven Projects’, as presented at the CIB World Building Congress, Tampere Finland on June 3, 2016.
The topic is in constant flux: new definitions and approaches are being developed and existing definitions are constantly revised. If you discover any inaccuracies or would like to highlight missing information, please add a comment below or contact the author directly.
Acknowledgements
I would like to thank Bilal Succar for this opportunity to publish through BIM ThinkSpace. I am thankful to Brian Renehan for his comments on earlier works and for exchanging thoughts on different Model Progression Specifications. I would also like to acknowledge the assistance provided by graphic designer Fabiola Pizzuto. Prof. Angelo Ciribini, Amarnath Chegu Badrinath, Prof. Shang-Hsien Hsieh and Zhe Liu. Finally, special thanks to my grandfather for his constant support.
Guest Author
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Marzia Bolpagni Architectural Engineer | PhD Candidate at Politecnico di Milano, Italy Marzia Bolpagni is a PhD Candidate at Politecnico di Milano (Italy) where she is investigating ways to manage and control public works through innovative digital approaches. She has worked as BIM researcher at VTT (Finland), ITC-CNR (Italy) and Massachusetts Port Authority (US). She also worked with designers, contractors, public authorities and the Italian Standard Body (UNI) on implementing BIM-based processes. She has presented her work at both national and international fora. After serving as a member of the WBC16 International Scientific Programme Committee for the CIB World Building Congress 2016 and the BIM Roundtable at AIA BSA Foundation, she is currently a member of the VDC & MEP Committee Roundtable at Associated General Contractors of Massachusetts (AGC MA). Marzia can be contacted through LinkedIn, Twitter, ResearchGate, and Academia |
Comments 34
Excellent work, as usuaslly. Always surprise usuarios with brillants articles. Congrats
Thank you David. Your feedback is appreciated!
Thank you David for your positive comment. Best Regards, Marzia
Thanks Marzia
I envy your writing and presentation skills. I think you have achieved a much better outcome compared to my post on a similar topic. It is great to have a fellow LOD blog writer, as I’ve have been getting lonely lately. I also love the new acronym cLOD, and we all have come across the cLOD in construction.
For the other eager LOD researchers and patrons, Marzia and myself have discuss how best to compare the platter of MPS/LOD systems out there. The above post elegantly communicates a very easy to read comparison where the different systems align within columns. The vital statement in the article is “there is not a perfect coincidence between levels of different classifications and some of them are not well defined”.
I tend to feel that some of the core principles of the AIA’s Level of Development concept are fundamentally poles apart from the UK PAS 1192-2:2013 Level of Definition, and thus a linier comparision is very difficult.
AIA – Level of Development: “the degree to which the element’s geometry and attached information have been thought through”
UK Level of Definition: = “level of model detail” + “level of information detail”
“The “level of model detail” is the description of graphical content of models at each of the stages defined for example in the CIC Scope of Services.
The “level of model information” is the description of non-graphical content of models at each of the stages defined, for example, in the CIC Scope of Services.”
A practical comparision example below:
UK Level of model detail for stage 5 (Construction) i.e.: LOD5 / LOI5
From PAS 1192:2-2013 Figure 20:
Shall include (below list is only some of the requirements):
• Detailed construction methodology
• actual dimensional data for critical interface dimensions
• Detailed design and construction programme
• object procured from the manufacturer
• fabrication and manufacturing details
• capture of as-installed information
• Modify to represent as installed model with all associated data references
• Operation and maintenance information
Thus to compare the UK LOD5/LOI5 to AIA LOD & BIMForum LOD Spec, it contains aspects of LOD 300 (e.g.: Architectural construction set-out drawings/models), LOD 350 (e.g.: MEP sub-contractors coordination model), LOD 400 (e.g.: Steel Fabrication Model) & LOD 500 (As constructed elements).
LOD is a complex topic. I get to see first-hand how construction professionals incorrectly engage filtered simplified information, and implement it incorrectly.
So that’s my bit of controversy to the topic. I hope others in the industry have some spark, and decide to contribute accordingly. If you are really interested in this topic, after reading Marzia’s Paper, pop over to the BIMFix Blog, and there are months of agonizing reading on the subject. And like Marzia says: please tell us when we are wrong. We don’t bite :-).
Great point Brian! Thank you very much. Marzia
Congratulations Marzia, your article is extremely clear.
I think that a clarification of this topic (and also of many other standards/protocols about BIM) such the one you made, is something that many of us really need.
Thank you!
MicheleC
I appreciate both Marzia’s and Brian’s articles on this topic as they highlight the need to coordinate the efforts in this field. I see this lack of coordination as really the only negative.
As someone who works purely with data (spec and geometric) algorithms I would like the solution to simple be the following:
1. LoP (Level of Progress) – which would be the same as level of development (just eliminating the use of “D” for clarity sake) and would indicate how valid and accurate certain details of LoI and LoD are. Basically it would meam you could have detail in the model but only certain aspects should be considered definite based on how far the project has progess through its life cycle.
2. LoD for geometry
3. LoI for information
Obviously different elements can be a different levels but for a project to achieve say LoD 300 every element would have to be at least at that level. I think it is unreasonable to ask that every element is at the same LoD for delivery because this would require some very well synchronized and intelligent processes, which personally I am developing within my own content but I think is unreasonable for all elements.
Thanks for your hard work Marzia and Brian.
p.s. Brian I feel your pain, GDL is also a lonely realm.
Thank you Michele for your feedback. Glad to know it is useful for you. Best, Marzia
Thank you Kristian for sharing your point of view. In your opinion, is it possible/useful to define a common classification related to LoD and LoI (e.g. 100-500) suitable for different Model Uses? Thanks Marzia
Good Job Marzia; very usefull !
Actually, in Luxembourg, we’re working on a kind of LOD but I canno’t say more because It’s in progress and confidential.
Kind regards;
Laurent HENIN
Dear Laurent, thanks. I am looking forward to hearing more about your work in Luxembourg when available. Let’s keep in contact. Best Regards, Marzia
Good reference for the future.
Thanks, sometime the problem is to find an agreement with partners and clients about input despite of the Lod.
Thanks Vito. How the current situation could be improved in your opinion? Best, Marzia
Im really amazed from your perspective of opening the LOD Subject which I believe as you said is a very important subject and still in so many countries including UAE, is not clarified among most stakeholders.
The highlighted point for further research are very thoughtful, hope to see further articles from you in the future.
Dear Donya Mehran,
thank you very much for your comment. I am looking forward to sharing research developments. However, working with industry is the key. I would be glad to further discuss with you on this topic. Best Regards, Marzia Bolpagni
Marzia, I think it would be very useful (and convenient) however it may be too restrictive. I believe there should be some correlation between the two otherwise it would be making things unnecessarily complex. As the geometry is probably less crucial and requiring less variations I think it would make sense to perhaps have LoD 100 – 500 stepping 100 with LoI also 100 – 500 but stepping less then 100. You could for instance have 6 LoI’s in between LoD 100 and 300 (LoI 100,150,200,230,260,300) and then synchronized for the last two.
Dear Marzia, fantastic article.
I am starting to delve deeper in that subject and your article pretty much summed up all I have read and seen before.
I look forward to see your updates on that matter in the future.
Best,
Leonardo Acquarone
Dear Leonardo, thank you for your feedback! Best Regards, Marzia Bolpagni
Great article, will mention and share the link with the Revit User Group Auckland at the next meeting
Dear RobiNZ, thank you for your comment and will to share the post. I would be glad to know opinions of other members of your group. Best Regards, Marzia Bolpagni
Great article, I am excited to see that someone in Italy is involved with BIM in such a comprehensive manner. I am based in Greece, I am BIM BRE, (UK) certified and I am teachinng BIM through Revit in private institutions. I felt kind of lonely as there is no opportunities to practice BIM in Greece, there is no construction and no BIM application in the country. Keep in touch Marzia.
If you are interested please check my recent paper on “Building Information Modeling benefits for the owners”. Any comments are welcome
https://www.academia.edu/27455033/BUILDING_INFORMATION_MODELING_FOR_THE_OWNERS_en
Dear Nicoleta, thank you very much for your positive feedback. Let’s keep in touch. I would like to know more about the current implementation of BIM in Greece. Best Regards, Marzia Bolpagni
Good work!
Where there are many sellers of smoke, it is encouraging to find good work that brings clarity in this welter of acronyms and concepts that envelop the bim.
I learned some interesting things with your blog, Marzia. Thank you
Thank you very much Roger. I am happy the work is useful. You can find a lot of excellent posts in Bilal Succar’s BIM ThinkSpace blog, if you are not familiar with them. Let’s keep in touch. Best Regards, Marzia Bolpagni
Very good text Marzia. What I like most the approach from New Zealand, which I have already found a few months ago. I’m trying to promote it in Poland in terms of costing and scheduling in BIM.
Regards
Dear Krzysztof Zima, thanks for your comment. In my opinion the LoX definition in the New Zealand guide is not very clear (e.g How can you define LOD 200 ‘Level of detail’ (LOd) or LOD 100 ‘Level of accuracy’ (LOa) or LOD 300 ‘Level of information’ (LOi) or LOD 400 ‘Level of coordination’ (LOc) and so on?) Moreover, there is confusion between LoX of model elements and models. It would be interesting to know more about your work in Poland. You can comment here or contact me by email. Thanks. I hope to hear from you soon. Best Regards, Marzia Bolpagni
Great summary of LOD multiconcept! Very important in to be define in every BIM agreements.
Thank you for your comment. I am looking forward to further discuss on this topic with you if interested. Best Reagrds, Marzia Bolpagni
Great Article Marzia,
actually the BIM client plays a crucial role to define the LOD in his project, in addition the client BIM knowledge maturity is another point makes the client knows exactly what he wants from the Model.
in my opinion categorizing the construction projects types and the complexity level of them are important factors to choose the proper LOD which is matching the construction phase needs, equally the full coolaboration between the designer and the construction team at the very beginning of the project will help to define the required LOD to execute the project.
good luck & Best Reagrds
Dear Basel, thank you very much for your message. I am glad the work was useful. Best Regards, Marzia
Thank you very much for your great work. That was exactly what I was looking for and I really appreciated your article.
I am writing my master thesis in Germany within the same subject matter. My “job” is to define LoD-specifications for building elements for locks linked to different construction phases.
I only disagree with you in one point. You mentioned the authors Drobnik&Riegas, which are both architects for Herzog&deMeuron.
In their article about BIM in architecture they mention a “-100-Lod” and a “0-LoD” (ref: https://www.espazium.ch/uploads/56487ca4934af.pdf).
Both levels do not exist in Germany, as you signalize in Table 2 – Comparison of classification systems within different LoX systems – D&R(2015). Maybe in Switzerland but definitely not in Germany.
Nevertheless, the authors bring up a new perspective, as from their work as architects. Which is quite interesting, but in my opinion BIM is no design tool.
But maybe I get something wrong, so I would appreciate your comment.
As for my part, I’ll go with the LoD = LoG + LoI definition, and use the BIMforum LoD Specification.
Cheers Andreas
Dear Andreas, thanks for your comment. You are right, I will change the flag with the Swiss one when I will update the work. The flag does not mean that it is a national standard, it only represents the nationality of authors. Regarding your comment “BIM is no design tool” do you mean BIM or LOD? If you mean BIM, I think one of the use of BIM is design authoring. If you mean LOD, it is usually used as a reference for modelling requirements during different phases (design included). Good luck with your master thesis! Best Regards, Marzia Bolpagni
Great idea you have shared here over – LOD. Thanks fo sharing this with us.
Great Article