As part of the firm’s ongoing efforts to offer our clients a full range of high-quality surveying services, KCI has deployed a new $750,000 Riegl VUX-1 mobile LiDAR unit. The decision to purchase the equipment was based on our clients’ overwhelming need for mobile scanning, innovations in point cloud file storage, and new and improved solutions focused on 3-D corridor design. The unit has dual scanners, facilitating redundant data collection. The combination of a multi-lens 360-degree and three standard cameras shoot terabytes of photography as the system moves down the road at normal traffic speeds. Real-time GPS and inertia measurement unit (IMU) ensure data collected is calibrated accurately and registers the information to precise ground coordinates.
“The scanners are spinning in both directions, collecting up to two million points per second as the truck travels 60 miles per hour,” said Practice Leader James Clay. “The IMU understands trajectories and is tracking the speed so that all data is processed before download. We can also post-process the GPS to achieve an even higher level of accuracy.”
KCI has been a leader in terrestrial LiDAR for years, focusing mainly on site-specific or short projects of less than three-quarters of a mile in length.
Now the firm will be able to quickly gather data on longer lengths of corridor. In addition to supporting larger projects, mobile scanning offers a host of benefits to surveyors, engineers and owners, including:
1. Increased Safety of Field Crews Along Heavily Traveled Corridors
Mobile LiDAR minimizes and sometimes eliminates the need for staff to work in or near traffic. “Conventional surveying would require a rodman to walk across the street, stopping along the pavement to take critical shots in order to properly document a roadway section,” said Clay. “Instead, our team can digitally travel the corridor in the office, while taking the traffic, bugs, sweat, and wildlife out of the equation.”
2. Faster Data Collection than both Conventional Surveying and Terrestrial Scanning
Using a standard LiDAR system on a tripod, crews require about 15 minutes for setup every 300 yards along a corridor. A Total Station or GPS would require even more time because of the need to stop and take a shot at each critical feature. Moving at posted speed limits, the truck-mounted mobile LiDAR unit can scan longer distances in just a fraction of the time.
By driving down each lane of two-way and multi-lane roadways, redundancy of the data collection ensures improved consistency. KCI is working with developers to finalize algorithms that will identify any points that don’t appear in multiple scans, removing cars and people that were on the corridor during the scan.
3. Greater Density of Scanned Data
Most states require one-tenth of a foot density or intensity. Conventional survey crews generally collect points every 25 feet. The new mobile unit is accurate down to one centimeter or approximately one-half inch. “We may be collecting one dataset that has 10 million points from the LiDAR unit, which then gets filtered down to only one million points worth of data for us in CADD,” said Vice President Jim Gellenthin, PLS. “But all one million of those points are so much higher quality than the 1,000 points we may have taken conventionally.”
In terms of topography, contour lines are much more accurate due to the sheer number of shots taken. Data is collected across the entire surface instead of sampling every 25 feet. With more documentation of curb lines, utilities, etc., mobile LiDAR can significantly reduce the problems encountered due to gaps in the dataset.
4. Improved Data Compression and Storage
Datasets from the new unit are expected to be 10 times larger than those from the firm’s terrestrial scanners. Our team built new servers and processing computers that are the most powerful in the company and also plans to leverage cloud storage and sharing for our clients to minimize the need to download large files. “It’s critical that we create usable data for our engineers and clients,” said Clay. “We’ve tested pixel sizes and spacing in order to determine the best approach to deliver a lightweight dataset that offers accurate and extractable information.” Analysts are also developing new software that will automate the measurement and modeling of features.
5. Enhanced Quality Control and Visualization Capabilities
The extensive data collected also facilitates better review and quality checking. “It’s a lot easier to count fire hydrants, sewer manhole lids or water valves from your desk than to go out and start looking for them,” said Vice President Tate Jones, PLS. “If there is a question later in design, we can simply pull up the original data set and check without having to go back out in the field to confirm or collect additional information.” Color photographs and a full 360-degree scan also offer additional checking capabilities—if there is a question about the data, users can reference the imagery from the location to visually confirm the accuracy of the point cloud.
While initially focused on large corridor studies for transportation and power clients, our team anticipates deploying the mobile LiDAR unit on a variety of project types. By mounting the device on different vehicle types—gators, all-terrain vehicles, boats and rail cars—crews hope to scan:
Although the addition of the mobile unit to our robust inventory of terrestrial and drone equipment completes the firm’s full suite of scanning services, our team will continue to develop new solutions in data analysis, compression, storage and display, ensuring that KCI remains a leader among LiDAR providers within the engineering industry.