Tip#1  Ask for a workflow plan

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And make sure it answers the following questions:

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• What are the methods used for QAQC?

• What are the methods used for project control? (For most projects this would be Target Control (checkerboard and spheres) or Cloud to Cloud Control. Large projects (300+ scans) would benefit from Survey Control to reduce compounding errors.

• What is the proposed schedule and with how many workers on site?

 

Tip#2  Ask for Proof of Competency

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Other information to ask for prior to the beginning of work:

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• Samples of similar projects. Screenshots with short descriptions. At least three of them. 

• Years the company has been providing laser scanning services.

• Laser scanner certificate of calibration. (This is done yearly)

• References for larger projects.

 

Tip#3  Be Very Clear

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It is critical to be very clear on your intent. Laser scanning can be used for a variety of reasons and our approach to each project is different depending on what you need as a deliverable.  

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• Let them know if you want coloured scans or black & white. Coloured scans are nice, but B&W saves a lot of time. 

• Let them know what to focus on. If piping is very important to the project, make sure they capture all of it. Stuff like that can get overlooked as you don't always go in every nook and cranny while scanning. It's especially easy to miss stuff overhead if you’re not looking for it.

• Be very clear about why you want to use laser scanning. Do you intend to use the point clouds to produce 3D models, floorplans, pipping drawings, or simply to check clearances? This makes a big difference on the scanning resolution settings used and on the amount of scans taken.  

• They need to know what level of accuracy (LOA) you are looking for. For more information on LOA, click here.

 

Tip#4  Ask them what tools are they using

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Point clouds can be created by different devices. Some are more accurate than others and it is important to know the difference.

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• Terrestrial laser scanner: This is the best tool if you’re looking for great accuracy and resolution.

• Hand-held laser scanner: This is the best tool for speed. Although very fast, the accuracy is nowhere near that of a terrestrial scanner.

• Camera: Photogrammetry produces very attractive point clouds but the technology hasn’t reached the level of accuracy of either terrestrial or hand-held scanners.

• Drone: Drones are great for large outdoor areas. This is the best tool for volumetric calculations and a handy tool to supplement terrestrial scanners. Sometimes roofs are not accessible to terrestrial scanners and point clouds taken from drones can be added to create a more complete point cloud.

• Total Station: These devices are extremely accurate. They are a surveying tool using GNSS positioning and are used for survey control on large laser scanning projects.

• Multi-Station: This is a combination of total station and laser scanner. These devices are also extremely accurate. The downside is that they are very slow at producing point clouds and only intended for small projects.

 

Tip#5  Know what you are getting

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Make sure both parties agree on deliverables   

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• Let them know what file format you want as a deliverable. RCS and E57 are the most popular ones.  RCS is compatible with most Autodesk products and E57 is pretty universal. 

• Make sure you ask for the Registration Report as a deliverable. This will show you how much error was introduced by registering the scans together. Every scan has a tiny error, and they accumulate with every scan. If done right, you can eliminate a lot of that error. The report will show this.