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An interview with a survey crew on a 3D scanning project

Alain Calle, Visual Communications Manager, spent some time with Reid Middleton’s 3D Scanning crew discussing the surveying of a large, working aircraft hangar.

A – How did this scanning project come about?

Byarn – The client is looking to use an existing aircraft hangar to perform maintenance and other work on large transport planes. The hangar is very large, able to handle two planes at once, but the problem is that the tail fin of these aircraft is too high to pass under the current hangar door configuration.

Tim – We saw this first-hand while we were surveying since they were working on an aircraft with its tail section hanging clear out of the hangar.

Byarn – Reid Middleton’s structural group was hired to design an entry reconfiguration, which will entail moving a number of critical utilities such as water/fire lines. They are designing a vertical notch section in the wall above the existing hangar doors that can open and close when needed to move planes in and out. To do this, they need to know where everything currently lives: support columns, beams, water lines, conduit, the engine hoist removal system, railings, etc. The new design has to account for the planes’ new location once they are able to roll them all the way in and any reinforcements of the exterior walls once they are cut, reconfigured, and a new notched door system installed.

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A – What were your individual responsibilities on this project?

Preparing the instrument for a scan

Byarn – Since this was an out-of-state survey, I was responsible for getting us and ALL the equipment we would need to the site safely. I also had to make sure we had everything properly scanned before leaving five days later. All our work was done in close coordination with the on-site manager, especially since it was an active site with an aircraft being worked on inside and aircraft activity on the flightline. I made sure to communicate with them everyday. We didn’t want to be in their way but we needed to get our job done within the time we had been allotted.

Tim – As survey tech, I was responsible for the care of the equipment. I made sure it was properly charged, calibrated, and ready to go every morning. I checked our scans to see if they were comprehensive enough on a day-to-day basis. We processed and emailed our scans every night to our Everett office for analysis and review.

Byarn – They would let us know the next morning if we had holes or needed to retake a section of the previous day’s scan.

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A – Was this project technically challenging in any way?

Scanning setup

Byarn – As in any survey, we first needed to set up our control points both on the outside and the inside. This site was a little more complicated than usual since we had a hard time finding any local control information. On the inside of the hangar we had 12 control points on the empty half of the hangar and a couple more on the other half to enable us to work around the aircraft parked inside.

Tim – From those points, we had a total of 40 scans, having to scan features from multiple angles to get a good 3d representation. Each scan gave us more than 400,000 data points, which ends up being a lot of data!

Byarn – This hangar was especially challenging because of the inset nature of some features, in particular on the ceiling. The ceiling was not one flat plane but had beams and skylights throughout. The skylights were a unique challenge as they had critical water/fire lines and sprinklers tucked up into them. For the sake of accuracy and productivity, we used the overlapping 90 degree scan technique instead of a “dome scan” technique. This type of scan unfortunately does not allow for a full 360 degree scan, which made getting good scans of those skylights a little more complicated, and we ended up having to take multiple scans from multiple locations. We discovered that removing the carrying handle from the instrument allowed for a couple more degrees of rotation which helped.

Tim – The aircraft being in the hangar at the same time also posed a challenge as we were scanning. We had to make sure we were scanning in such a way as to not show the aircraft and not have it interfere with our final data output while still showing all the little details of that hangar, its construction, and infrastructure. Each scan took 20-30 minutes.

Example of a 3D Scan

Byarn – 3D scan technology helps to reduce the cost and labor when working on large sites. It gives us more data faster and creates as-built 3D models that can then be morphed into BIM. This hangar had a lot going on, including fire barriers running one way, beams running another, as well as water and electrical lines twisting and wrapping around the columns and throughout the ceiling. Even though the scan “locates” everything, the scan data points don’t have actual information in them other than an X,Y,Z location. To supplement the scans, we located the beams, connections, bends in the water lines, etc, using a reflectorless total station instrument with annotated data points. Reflectorless technology made it fairly easy. One of us aimed the instrument while the other operated the data collector. Efficient, accurate, and safe since it allowed us to stay on the ground while still getting all the information necessary for our structural design team.

Tim – Combining the two is the best of both worlds. Since they are both based on the same XYZ control, we superimposed both sets of data to get the density of the 3D scan and the detailed information of a standard survey. We can also rotate the composited data in three dimensions to look at anything from practically any angle.

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A – What was your overall experience?

Byarn – It was exhausting, but fun. I enjoy road trips and one where we were able to use 3D scanning skills was even better. This was a good project that enabled us to push ourselves and the technology.

Tim – Great weather and a good experience, but as it seems to happen on all of our road trips, we had one bad meal.

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