Laser scanning and automated feature extraction streamlines plant upgrades through faster BIM.
The 60 million travelers who pass through the Los Angeles International Airport (LAX) every year likely never think about the technology that ensures hot and cold water flows uninterrupted to lavatories, kitchens and air conditioners throughout the facility. They would, however, notice if the water stopped running. And for Los Angeles World Airports (LAWA), the proprietary department of the City of Los Angeles that manages and operates LAX, that simply isn’t an option.
Ten rooms equipped with massive pumps keep water moving through miles of pipes serving the nine passenger terminals, administrative offices and central theme building. With many pumps and pipes approaching the ends of their useful lives in 2011, LAWA made plans to overhaul the outdated central utility plant and upgrade the pump rooms. As is true for any continuously operating facility, the challenge was performing the retrofit without disrupting service.
“You can’t just take out the old pipes and put new ones in their place,” says Scott Cedarleaf, co-founder of Cedar+Mac, a scanning, modeling and visualization firm based in based in Scottsdale. “The new pipes had to be installed before the existing ones were removed.”
This meant the pipe runs had to be precisely modeled in 3D to fit in the void space among the maze of existing mechanical, electric and plumbing (MEP) features in each room. The location, diameter, bend and sag of each new pipe had to be exact to pass cleanly through the allotted space. A misalignment or encroachment would have brought the construction to an expensive halt for redesign and procurement of new parts.
For a major plant retrofit like this, the design work is typically performed on workstations in the CAD environment and requires an extremely accurate 3D as-built model of the existing MEP infrastructure. Visualization firms like Cedar+Mac generate these models by performing high-definition surveys with terrestrial laser scanners. A highly accurate scan of an interior room can be captured in minutes with the laser.
Cedar+Mac, however, adopted a method of further streamlining the entire 3D modeling process for industrial plant projects by using software called EdgeWise Plant, which automates the extraction of pipe features from the laser point cloud. Deployed at an earlier LAX project, this fast and accurate modeling technique caught the attention of construction giant Clark McCarthy Joint Venture (CMJV), which invited the visualization firm to join its team for the water plant upgrade.
Each LAX pump room has a different configuration but averages about 50 feet in length by 30 feet in width. The center is occupied by one or more pumps, while the remainder of the room is crisscrossed by electrical wires, conduits and pipes ranging from 1 to 24 inches in diameter. MEP features in the rooms are color-coded according to industry standards for easy identification based on their function.
Cedar+Mac has several laser scanners in its inventory for different applications and environments. Due to the relatively small size of the LAX pump rooms and their hot, humid conditions, the firm selected the Leica HDS6200 phase-based scanner, a fast and rugged product designed for smaller spaces. As the name implies, these stationary scanners use rotating lasers to collect a point cloud containing thousands of precise measurements from the device to the surfaces of every exposed feature in the room.
“In each room, we usually take a center scan to get the basic geometry and then set the scanner up at multiple other points depending on obstacles,” says Cedarleaf.
The challenge was placing the scanner at enough points in the room to capture all of the features and void spaces, he explains. This was difficult because the rooms were so packed with pipes and conduits running in all directions that most features were partially blocked from view in at least one direction. In square and rectangular rooms, the scanner was set at regular grid spacing, but the placement became more random in the oddly shaped areas.
“Throughout each room, we set up black-and-white targets that would appear in multiple scans,” says Cedarleaf. “These are the control system that ties multiple scans together into a 3D model representing the whole room.”
To capture photographic information along with the laser point cloud, Cedar+Mac attached a Nikon D80 digital camera with fisheye lens to the top of the scanner. The 12-megapixel camera took high-resolution panoramic images from the same perspective as the device at each position in the pump room. Referred to as RGB information, these photographs are valuable because they help differentiate types of pipes by their color.
Due to security restrictions at LAX, the scanning had to be completed in one visit. It took 16 hours to scan and photograph the 10 pump rooms.
Back at Cedar+Mac headquarters, Leica Cyclone software was used to tie together the multiple scans for each room into a single 3D point cloud model with minimal data gaps. The software also “texture mapped” the point cloud with RGB values taken from the panoramic photographs, creating a photo-realistic 3D view of the pump room. This brought to life the standardized color scheme used to identify MEP elements.
Prior to the availability of the automated extraction software, the next phase in the project would have been the most time-consuming and would have introduced accuracy errors. Working in a tracing application, Cedar+Mac technicians would have had to manually delineate and extract features from the point cloud, one pipe run at a time. This meant precisely locating each pipe section by its X, Y and Z coordinates, carefully measuring its diameter and correctly determining elbow bends. “When extracting features manually, the tendency is to model pipes in straight lines,” says Cedarleaf. “But pipes don’t run that way--they sag.”
Accurately estimating the radius of an elbow, where two pipe sections join, is the other difficulty in manual extraction. Incorrectly determining the radius by just a fraction of an inch can negatively impact the fit of the two pipe sections at the connection. If those dips and bends aren’t represented precisely in the as-built, the accuracy of the 3D design may be thrown off, resulting in a sagging older pipe interfering with installation of a new one during the construction.
The tedium and human errors related to extracting features manually from laser point clouds have been a challenge to surveying and mapping for decades. The airborne LiDAR market dealt with the issue first, and two former U.S. Department of Defense scientists who pioneered these efforts later established ClearEdge3D Inc., a private firm in Herndon, Va., to apply automated feature extraction algorithms in terrestrial laser scanners. “Building information modeling (BIM) is a rapidly emerging field that requires 3D as-built models,” says Tim Lowery, vice president of business development for ClearEdge3D. “We developed EdgeWise Plant software to improve the speed and accuracy of creating these models and associated database layers.”
For the LAX pump rooms, Cedar+Mac technicians exported the registered point cloud from Cyclone to EdgeWise Plant and then set parameters to extract all cylindrical pipes greater than 1-inch in diameter. From there, the extraction process was automated. The software progressed through one scan at a time identifying, locating and measuring the pipes, and saving these pieces of data into a table.
Built-in quality control functions ensured the pipe sections fit together precisely, especially at elbows where the radius measurement is exacting. The software also correlated scans in a single room to ensure that pipes partially occluded, or hidden from view, in one scan were picked up in another scan so the entire run was accurately located along its full length.
The software successfully extracted even slight dips and sideways turns in the runs. “The software takes into account all of the changes in directions and connections in the scans, and then makes sure all the pipes align,” says Cedarleaf. “That was fantastic for us.”
The technicians typically set up the extraction software to run on one or more scans overnight. Once the extraction was completed for a room, EdgeWise Plant allowed the technicians to manually connect any pipe runs the software couldn’t align due to extensive occlusions in the scans. In one final automated step, the extraction software smoothed out all the pipe runs and modified the diameter to the correct ASME standard. Cedar+Mac estimates that 85 to 90 percent of the pipe extraction was performed using the automated software. “Even having used the extraction software before, we estimated the 3D modeling of all 10 pump rooms would take us three months,” says Cedarleaf. “But we finished the project in 30 days.”
Other EdgeWise Plant users have reported similar workflow savings, according to Lowery.
Cedar+Mac transferred the registered point cloud and solid pipe model from EdgeWise Plant back to Cyclone for tweaking. The technicians added valves and connectors, and aligned them with the pipes in the solid model. From Cyclone, they generated three deliverables on a per-room basis for ARUP, the engineering firm designing the plant upgrade in AutoCAD MEP. The first two files were RGB texture-mapped point clouds in .ptx format, one including all of the individual scans and the second containing the unified 3D cloud for a given pump room. The 3D solid BIM with the pipe data layers was delivered in .dwg format. “We matched the 3D models and point clouds to the coordinate system they were using in their CAD design,” says Cedarleaf.
With the 3D BIM imported into AutoCAD, ARUP design engineers could view every pipe in the pump room from any perspective. Autodesk Navisworks also allows the designers to merge their proposed pipe network layout with the as-built BIM. The software automatically identifies where clashes and encroachments occur. The model lets the designer see what the obstacle is and determine whether it can be easily moved during installation or whether a re-design is required.
“The entire engineering design goes much smoother if an accurate 3D building information model is delivered early in the process,” says ClearEdge3D’s Lowery. “The automated feature extraction helped our client deliver the BIM to their client two months sooner, which had a positive impact on the whole project.”
For more information about Cedar+Mac, visit www.cedarmac.com. Additional information about ClearEdge3D EdgeWise Plant can be found at www.clearedge3d.com.