Top 3 things to consider for Big BIM--Webinar today 1pm

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Kevin
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Top 3 things to consider for Big BIM--Webinar today 1pm

Post by Kevin »

We are going to discuss these comments and more on our Big BIM webinar today at 1pm EST. More than 450 have registered and the case studies look really interesting.https://attendee.gotowebinar.com/regist ... 5016377346
Last edited by Kevin on Wed Feb 18, 2015 5:06 pm, edited 1 time in total.
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Kevin »

I'm gathering data for the Big BIM webinar and finalizing the deck tonight. Any comments from the Forum would be helpful and fully attributed.

This is from Mark Hanna at PrecisionPoint...more to come!

1.) Have a survey network established through-out the project for dimensional control of scanner targets to verify point cloud alignment and registration. The survey network serves as the backbone to accurately tie-together smaller clusters of scans making a large project more manageable while ensuring project accuracy tolerances are met.

2.) Have a field execution plan established…often very large as-built BIM scanning projects require multiples crews and scanners working together on the same project. To avoid redundant coverage and potential voids in the scan data its essential that each scan crew has well defined field plan established. For instance, the field plan should include coverage maps broken down by crew, file nomenclature, and what pre-determined targets will be used for tie-in and verification to survey control network.

3.) Better manage downstream point cloud modeling workflows by Geo-refernecing point cloud to a known project or "real world" coordinate system (i.e. State Plane, project coordinates, building gird, etc.) enabling multiple modelers to work on different portions of the same project in the same project coordinate system.
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Oatfedgoat »

Hi Kevin,

By "as-built" do you simply mean capturing existing site conditions at the start of a project, or validating/creating a post construction record?

I think it's one of those regional differences where certain things mean something to us strange Brits over here and to the rest of the world it is something different.

"As built" over here is generally referred to as post construction.

My 3 questions would be very different depending on which it is.
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Kevin »

Hi Matt,

Yes...as-built meaning post-construction. Documenting of existing conditions typically for a refurbishment project. Love to get your thoughts as i know you've got a ton of experience with big projects. --K
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Matt Young »

just some things I have learnt about so called BIM.

Number one - most of us have been doing level 1 BIM for years and then it got a name (BIM!). An AutoCAD drawing can be considered building information and is just as relevant as a 3D model in certain cases.

It's important to understand when to use OS or state plane coordinates in a project.

All Buildings are designed on a local grid that is square to the building. This makes it easier to work when drawing straight lines and general viewing of the model. It's important to have the global position of the building related back to the local system. A building would never be designed in a global coordinate system because it generates all sorts of problems (32 bit floating point) in the numbers used to describe the 3D model.

Take Revit as one example of a scan to BIM exercise (Revit is not BIM by the way ;) )

You scan and register your data in the OS/State plane system and then assign a local system to the data. Using the best mean fit of as many long straight walls as possible to find the square to grid orientation. The position of the data should allow all of the building subject to be in as small as possible positive coordinate system.

Using the transformation between the new local system and the OS/state plane system it is a simple matter of assigning the shared coordinate system to the model.

Understand how to clean, process and deliver point cloud data in the most efficient way possible. Just indexing a bunch of registered data is not enough in my opinion.

When it comes to the actual modelling of the building it is important to understand the level of detail required and especially the desired scale of the final drawings that may be produced. For example, if a wall deviates by 20mm and the final drawing scale is 1:100 then it's pointless to try and draw the wall with the deviation, just average it out based on 10mm either end. Only skilled building surveyors and architects will fully understand this concept.

As surveyors we don't do BIM - we simply document what we survey and integrate that with the BIM process used by others.

Collaboration is a word used a lot by people in the industry. It doesn't always work, on a project with a fixed lump sum for example... because when the money runs out the work stops... to put it bluntly. Be careful what you sign up for when working in the world of BIM or you might find your doing more than you bargained for!

BIM execution plans (BEP's) work for architects but they will rarely include you as the surveyor in that plan. Make you own plan about what you are going to do, show to the client and then get them to sign it off before you start.

More than three points I know... I have a hundred more if anyone is interested ;)
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Oatfedgoat »

Kevin, I am sure most of this is obvious to you based upon your R & D and you have heard it many times over.

1. Do not make a brand new model just for the as built. This is duplication/waste - which is the opposite of what BIM strives to achieve.
Not to mention the extra time and cost this incurs, it also will lose so much of the valuable Information part of the BIM that the designers/engineers etc put into populating their elements to start with.
Validating a final design intent or fabrication model to become the as built is the best route?

Each type of element could have a different level of accuracy that is required. For instance, structural elements should have far less tolerance than partition walls or ducts. As long as there is sufficient maintainable space around the M&E, it's absolute position could be 100mm+ away from its intended location and yet not really matter.

2. From the moment any site control is established, this should be done with the knowledge that post construction validation will be done.
This will ensure that the inevitable destruction of site control is mitigated with sufficient rendundancy to retain enough control stations across the site.

3. Do not simply do one post construction data capture exercise. This would result in the most important elements being missed from the as built.
For O & M of a facility, the most important objects will often be hidden. Be it M&E hidden behind a false ceiling or pipes burried in the ground.
Introduce an as built scanning activity to the project plan at pre-determined critical stages to create an as built verification that is almost in real time and close to producing a "Whilst Built" rather than as built.

This brings additional benefits to the as built process that will become amplified the larger the project becomes.
For instance, if it is continually found that a part of the M&E has repeatadly not been installed when the as built check is scanned, this is then a quantifiable and undisbutable record of it that could potentially be used in claims further down the line.
Identifying such a trend after 4 floors of a building are completed it will enable actions to be taken to ensure that it doesn't happen on the remaining 46 floors to be constructed.




I could go on and on even more on this subject, but I won't!
Hope these thoughts help.
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Kevin »

Great comments Matt and Matt! We need to get you guys presenting on our next webinar. Here's what Kelly Cone and Silviu Stoian at Beck had to say (pasted from an email and used by permission):

Provide specifications to the Laser Scanning Company
If you do not have any control over how the data is collected in the field and your company's SOW is to only take Laser Scanning data and convert it into a 3D Model, we recommend to work very closely with the Laser Scanning Company and establish some specifications that will be critical for the success of your project. On large projects we recommend using a Survey Control Network that will ensure the tightest registration, one coordinate system, and point cloud decimation.

Coordinate System
Regardless of the Authoring Tool used for developing your as-builts we recommend using the same coordinate system across the entire project. If your project needs to be on a specific coordinate system (i.e. State Plane) communicate that requirement to the Laser Scanning Company and make sure their data is on the same coordinate system as your Model. The reason for using the same coordinate system across the board is to have consistency and avoid manual alignment of the data. This will save a lot of headache and eliminate the possibility of accidental movement of data.

Data Management
Big projects can have between a couple of hundred scans to a couple of thousands scans. Managing your data sustainably is one of the most critical steps. This is where using the same coordinate system for both the Model and the Point Cloud comes into play. It will allow you to divide the data into manageable sizes without worrying about how are they going to be stitched back together once inserted in the Authoring Tool.

We also found that decimating the data used inside the Authoring Tool it can noticeably increase the performance of the software. Furthermore, it decreases the size of the Point Cloud files tremendously. By intelligently decimating the final user is not sacrificing the resolution of the data, but rather purging all the data that is redundant (i.e. overlapping point captured from various scan locations)

Tools
There are a lot of solutions on the market when it comes to tools that can improve your workflow. In order to increase your productivity you need to identify opportunities where tools that help automatically identify and extract geometry. On a big project using the right combination of tools can provide a competitive advantage in the marketplace.

Standards and Templates
On big projects the team can be comprised of a large number of people of various levels of expertise and backgrounds. The project team needs to follow a well-established set of standards and use the same templates and content to ensure consistency throughout the project.
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Oatfedgoat »

I met Silviu at SPAR EU in 2013 when I was presenting on scanning for as builts and how the industry is not yet maximising it's potential in the BIM process.
I've not met Kelly, but have shared a few fun times in London with Beck's BIM manager, Aaron Maller. Damn those Texan's can drink!

You've certainly picked a great company to get input and feedback from with those guys. 8-)
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Chris Scotton »

This came in from Greg Hale, CTO at Hale TiP. Great stuff!

1. If this is your first large BIM or as-built project, don't go it alone. Find someone with experience with these types of projects and hire them on to mentor you through the process. Remember that it’s all of the things that you don’t know that will come back to get you later on.

2. Know the extent of software and subsequent hardware needed for the project. Does everybody on the team have the resources they need to participate on the project? The programs and storage necessary to deliver large projects can be very demanding.

3. Identify how project data is going to be shared and stored throughout its use for all team members. BIM files are large and scan data will be substantially larger. Setting up a cloud-based repository for BIM workflows and scan data can be helpful to share the info across a dispersed project team. Portable hard drives are the most common delivery and storage method.

4. Understand the scope of work completely so that the as-built can fully serve the needs of the project. As-built data needs to be captured at an appropriate level of detail to serve those needs.

5. Don't restrict the use of the data. There are others on the project team that might have a use for the as-built information that you did not foresee. Offer it freely to architects, engineers, builders, subcontractors and owners.

6. If you're hiring out a 3D laser scan, make sure to obtain the raw scan data as well as the registered scan data in it's native format, not just a final as-built BIM. This will allow for things like feature extraction and future uses in case you need to add or replace scans later. It also provides you the best chances of exporting the data to other formats.

7. Divide the project into smaller segments by scope of work or by area. This allows the project to be viewed and worked on by multiple participants in manageable sizes. It also allows for critical data to be delivered early since often the project is waiting to kick-off until after as-built information is captured and delivered.
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Re: Top 3 things to consider when doing a large as-built BIM

Post by Matt Young »

All good stuff, but I still don't agree with the statement about using only one coordinate system. The local system for a building is more important at construction phase than the global position. It's important to know the global position and therefore at least two coordinate systems will be required.
Kevin wrote:Coordinate SystemRegardless of the Authoring Tool used for developing your as-builts we recommend using the same coordinate system across the entire project. If your project needs to be on a specific coordinate system (i.e. State Plane) communicate that requirement to the Laser Scanning Company and make sure their data is on the same coordinate system as your Model. The reason for using the same coordinate system across the board is to have consistency and avoid manual alignment of the data. This will save a lot of headache and eliminate the possibility of accidental movement of data.
I'm only mentioning Revit here because it's mainly what we get asked to use. Revit does not allow core model coordinates outside of twenty miles (used to be two miles) - The reason for this is that it is unlikely for a building to be larger than that or even close to that size. The global coordinates for a project are added by mimicking the origin rather than moving the model all that way. Maybe other authoring tools have a better solution to this problem but I don't know of any right now.

And also the point about point cloud decimation... It is clearly not understood. The comment mentions removal of overlapping points and that it not the same thing as decimation. Decimation tries to remove points based on a cubic algorithm and leaves the data sparse and un-readable if taken too far. Removal of overlapping data is done by segmenting individual scans prior to a unification process. If the unification process is done correctly and decimation values set correctly the data will be optimized. Only careful segmentation of the unified and correctly decimated data into manageable parts will allow for an easier workflow.
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