Clay added that a specially designed tilt bracket boosted productivity and safety by allowing scanning from one level. He tilted the scanner at a 45-degree upward angle and entered the project number into the GLS-1500 keypad, including his initials in the event that Fugera had questions about the locations of any points in the cloud later. Since this scanning sequence covered the eighth level on the south side of the building, Clay named the first scan 8S-1 and the targets T1, T2, etc. Clay scanned the targets from left to right and then bottom to top.
Using the Scanner
First, Clay dialed the top of the GLS-1500 turret head to the left using jog wheels located on either side of the turret head. He used the instrument's sighting columnator to aim the GLS-1500 toward the upper right corner of a steel frame for a parapet located just above a block wall to his left. After waiting several seconds for the instrument to calibrate, he scanned the first target. Next, he swung the turret head to his right toward a target located on a vertical steel beam on a flat wall just below the guitar wall. "We'll scan all of the targets first, then we'll set up a scanning area and all of the points will be inside of that area," he said.
Clay used a total of seven targets for his control; it is recommended that at least four targets be scanned. After all the targets were scanned, Clay set the scan area by turning the turret head to an arbitrary point at the top left and an arbitrary point at the bottom right of the area he wanted scanned. He input the desired point density on the keypad. The point cloud was defined by these arbitrary points. These points were slightly outside of the control targets so that previous and future scans of nearby areas could be blended together. Clay then confirmed the area to be scanned and the scan commenced.
Putting the Data to Work
After Clay finished the scanning sequence, raw point cloud data were copied from the data card in the GLS-1500 and sent to Adam Arrington, PE, vice president at Earl Dudley. Arrington received the point cloud data, scanned images, and a file containing control point data and imported them into Topcon ScanMaster software. He registered the data together in ScanMaster, essentially performing quality assurance/quality control on the data, and stripped the file down into Schuff's steelwork and surrounding structures that Fugera needed to view in order to ensure correct relative positioning.
Taking a PCG file provided by Arrington, Fugera imported the point cloud and dimensional data into AutoCAD using kubit software. The kubit software allows Fugera to compare the point cloud coordinates with the AutoCAD building model that is based on the official survey. ScanMaster Viewer allows him to view images of Schuff's steelwork from where the scanner was located and point coordinates. Along with the ScanMaster and AutoCAD files, Fugera viewed Schuff's steelwork against the entire building structure on a Tekla Structures file developed by Schuff's drafting department.
"Once I get a scan, I primarily use ScanMaster to make sure that I've got everything I need, and if I don't then I direct [Clay] to do another scan in a different area to catch what he's missed," Fugera said.
The modeling process allowed Schuff to make immediate incremental corrections to its steelwork when necessary. "Using the point cloud actually locates [the steelwork] exactly where it is compared to where it should be, using base control that we establish throughout the building and through the 3D model showing where it's been designed to be," Fugera points out. "The scan and the point cloud give me an exact picture of where everything is. I'll go through and start pulling dimensions; if I can see that any points are off of my model, I start writing down what's got to move, how far and which way. The point cloud and the scan give me the whole face of the building and let me know exactly where everything is."
Don Talend of Write Results Inc., West Dundee, Ill., is a print and e-content developer specializing in covering construction, technology and innovation.