How Drone LiDAR Helped the Road Race after the BC Flooding
The natural events of mid-November 2021 caused major flood damage to more than 20 sites along 130 kilometers of critical BC highway. Among the damaged were seven bridges that were severely compromised. Companies and their crews from across the province came together in a herculean effort to get these major highway arteries back in operation, among them of course was BC's #1 drone LiDAR service provider, Rekon Solutions Inc.
To make repairs as fast as possible, the province divided sections of the damaged highway up between capable contractors. Peter Kiewit Sons ULC was made responsible for a portion of the highway north of the Coquihalla summit. Before major work could start, Kiewit needed to asses the damage and quantify the scope of repairs required. It was then decided that detailed 3D models of 7 key sites were needed. To produce these detailed models of the land, highway and bridge structures a method called LiDAR (light detection and ranging) was contracted. With hundreds of LiDAR missions worth of experience, our LiDAR team at Rekon was a perfect fit for the job.
LiDAR is a method or technology that combines 3 main components, a laser scanner, an initial measurement unit (IMU) and a global navigation satellite system (GNSS). Each plays an important role to produce a 3D point cloud. A 3D point cloud is a dataset that can have millions of points, each point defining where a key feature like a road surface, pipeline, power line or railway is relative to trees and other natural features. Engineers can use this point cloud to model the current conditions of a mudslide or washout and calculate volumes, slopes and areas.
The first challenge our team faced was access. Without road access to get people and equipment to the target area, Rekon needed to take to the sky, naturally. Between the 20th and 21st of November, our drone lidar crew was transported by Summit Helicopters in a Bell 407. With the closest base of operations for Summit being Kamloops, crews had to fly for at least 45 minutes each way to get to site. Using a helicopter to get in and out of site means that crews had to wait to travel in at sunrise and finish with enough time to make it back to base before sunset. With 7 sites on the list, and 2 days to complete them, the team had to hustle.
To complete the scope of scanning and inspection in the shortest time span the Rekon team spilt up into two groups, LiDAR and visual inspections. By doing this, having streamlined checklists and hundreds of hours of experience deploying our LiDAR and inspection systems the team was able to complete the LiDAR scanning of 7 sites and inspection of the 6 sites just inside of two days.
The next big hurdle was how to get all 140 GBs of the data processed and transferred back to the engineers at Kiewit for them to begin the work of designing a fix. The most important things were to have accurate data, have it quickly, and in a format they could use right away. Figure 6 on the left is what the full point cloud looked like before removing trees and other features that were not ground from the model. The point cloud in Figure 6 without filtering had 148 million points, way too many points for designers to work with quickly or easily.
In Figure 7 on the right we removed the trees, powerlines and anything else not ground to reveal a point cloud consisting only of ground points. These points are what will be used to generate ground surface models. models that will be used by the engineering team to identify where the failures began and ended in the highway structure, where the new drainage path runs, how much volume is affected and how much volume of new fill will be needed to repair the affected areas. This new point cloud consists of only 829 thousand points, less than 1% of the original number of points, much more manageable for the design team.
Figure 8 on the left shows the final surface with contour lines overlaid. This surface model and these contour lines along with all the raw point cloud data and a full accuracy report were what the processing team turned over in less than 5 days. This allowed Kiewit and other companies like them to design and make the plans that repaired the Coquihalla highway in 35 days.
Bannet Braich and Gain Paolo Mendoza have written a article in CBC on the "Road Race". A story detailing how crews repaired the Coquihalla highway in just 35 days. We at Rekon are proud to have been called and able to help in the efforts to restore this important stretch of road. The BC Flooding is yet another reminder from nature that it's forces are immense and demand our respect. What we can also see here from this collective human effort is that, if we can all come together for a common goal we too can also do amazing things.