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25 Tips for BIM

This entry is part 2 of 8 in the series xyHt in print April 2015

Expert Recommendations for Better As-built BIMs

Creating as-built building information models (BIMs) has been greatly facilitated by the introduction of 3D laser scanners and modeling software, but the process still has its challenges. Four experts were asked to put their decades of combined scanning and modeling experience into this list of the best tips, tactics, and tricks that you can apply right away to create better as-built BIMs. These 25 recommendations are categorized according to where they fall in the as-built BIM development process, from planning and scanning through to processing and delivery.

The experts are Matthew Byrd of DeWalt Corp., Greg Hale of Hale TIP, Mark Hanna of PrecisionPoint Inc., and Alex Demogines of ClearEdge3D.

Bidding and Project Planning

1. Communicate and educate. 3D scanning and modeling are still new enough that clients may not have a clear idea of what these processes entail. Educate them and communicate throughout the project so they know what is possible, and then deliver the detail they want.

2. Define the project scope. To get a clear scope of work, walk the client through the options. Do they want the BIM to include building interior, exterior, or both? Do they need MEP (mechanical/electrical/plumbing) modeled inside the ceiling tiles? Should the deliverable models be color or grayscale? 

3. Find out what features must be modeled. Ask how the client will use the BIM to know if the model should be tied to a coordinate system.

4. Walk the site. Take photos and make notes of the square footage and number of rooms. Also start strategizing how many scans you’ll need. This information will help you determine time requirements and overall project costs.

5. Consider deliverables. In preparing your bid, take product delivery into account. BIM files are huge. Can the client handle them? If so, do the files have to be converted to a particular format? Can you deliver them via the cloud? You may need to set up a remote viewing portal so the client can see the data over the web.

6. Plan your scans. You’ll need plenty of time onsite for scanning, so coordinate the timing with the client. You may be working in an active plant or hospital with access only during certain hours. Make sure you have enough personnel to complete the scans on schedule. Consider renting additional scanners to speed acquisition.

On-Site Data Collection 

7. Divide the project. The enormity of scanning projects such as sports stadiums and hospitals can overwhelm the entire process. Divide them into small segments. Let the crew scan one at a time and tie them together with survey control. This results in smaller files sizes that are easier to process and register. 

8. Know site conditions. Be aware that areas of high reflectivity, vibration, and airborne debris can negatively impact laser scanning. Plan accordingly. Decide in advance where to put your scanners to avoid line-of-sight obstructions. If ceiling tiles must be removed, ask the client who is authorized to move them.

9. Practice quality control. Data accuracy is critical. Use survey references on site in combination with overlapping scans and targets to ensure you’re collecting accurate data that can be registered. Routinely check the calibration of your scanners.

10. Register the point cloud. Understand that targetless and targeted registration are available. Know whether the client needs the point cloud registered to a local coordinate system or survey control. Large projects need survey control and targets.

11. Place the scanner for maximum coverage. Know what information will be extracted from the BIM. If, for example, the client needs to know thickness of I-beams, you have to capture both sides of the beams in the scans.

12. Choose scanner settings based on desired point density. Scanning features that are small or far in the background require higher point density than larger features close to the scanner. But beware: automated extraction software always performs better with dense point clouds.

13. Scan more, not less. Capture as many scans with as high a density as you can. Extra data can always be edited or filtered, but if you don’t collect enough the first time, you have to make a return trip to the site. Clients don’t like that. 

Data Processing and Modeling

14. Go targetless. Try target-less registration. It’s useful, and it works. Use cloud-to-cloud and survey control to make it work.

15. Clean up the scan data. Before modeling, always filter the data to reduce noise and artifacts. This shrinks file sizes and improves the accuracy of automated extraction software.

16. Edit selectively. Remove unnecessary data, such as background features, for the CAD reference model but don’t throw the data away. Bring the extra data back in after feature extraction to create a complete 3D visualization of the scene without any black holes.

17. Coordinate CAD file origins and orientation before finalizing registration and translation. Clients love it when the BIM drops into place in AutoCAD. Set it up for them in their preferred coordinate system before delivery.

18. Borrow the client’s Revit template. If the client has worked with 3D models, they probably have a favored workflow and template that specifies sizes of ducts, pipes, and other features. Use their template to create your deliverable.

19. Don’t move scans in Revit … unless you have to. It’s not recommended, but is possible. If you move items, link scans by shared coordinates.

20. Go dark. A white background is the default in Revit, but you can switch to black, which comes in handy when presenting light-colored features.

21. Place Recap files on their own work sets. This allows the client to load smaller work sets as needed when they open a file, avoiding the system slowdown that can occur when a giant file is accessed.

22. Use View Templates in Revit. These allow you to standardize the graphics and overrides of typical views such as plans, elevations, sections, and 3D views to speed up modeling and provide the client with a quick way to make additional views.

23. Create camera views. Model from the position of the scanner for any point cloud. This position has the best data view and density, making for easier modeling. 

24. Use Navisworks for color walkthroughs. One of the best ways to check your models to find mistakes and missing data is to walk through it in Navisworks with both the point cloud and 3D model.

25. Try automated feature extraction. Scanning collects a lot of data accurately, but manual modeling is still time-consuming and error-prone. Newly developed software like the EdgeWise product line extracts features automatically from the point cloud so they can be modeled in their precise locations, orientations, and dimension. The time savings can be significant.

 

If the four experts had to make one overall recommendation for both 3D modeling beginners and veterans alike, they’d say, “Don’t be afraid of new technology.” New and improved scanners and extraction/modeling software are being introduced all the time. Keep up with the times, give the new gear a try, and you’ll likely see faster results and continue improvement on your bottom line.

 

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