Data fusion is helping surveyors deliver better results while satisfying higher expectations. Multiple data acquisition platforms, such as conventional land survey, mobile LiDAR, and aerial LiDAR, produce highly detailed comprehensive deliverables when used together.
CEC® is a multi-disciplinary engineering firm serving Oklahoma and Texas that has adopted the latest surveying technology, like 3D laser scanning, mobile mapping and unmanned aerial systems (UAS). By doing so, CEC has expanded beyond conventional infrastructure surveying and design to include advanced service offerings, including pavement analysis, dam monitoring and 3D visualization and modeling.
In an informative presentation at Trimble Dimensions 2022, Rusty Steel, Geospatial Practice Leader at CEC, and Bartley Estes, Remote Sensing Department Manager at CEC, explained how they are putting new technology to use. To explain more about how data fusion has impacted CEC’s work, Estes shared his thoughts.
Q. Bartley, what is your title and primary responsibility at CEC?
I work in CEC’s Geospatial Practice as Remote Sensing Department Manager. We handle conventional land surveys, remote sensing, subsurface utility engineering (SUE), and other projects that make use of a wide range of tools. My primary responsibilities are project management, mission planning, flight planning and control layout for remote sensing data acquisition, and on good days I get to go out in the field and get my hands dirty.
Q. How are changing expectations impacting surveying projects?
Advances in technology over the past decade have changed how surveyors work as hardware and software has become faster and more accurate, and that has increased expectations from end users—specifically, accelerated timelines and more comprehensive deliverables. At first, we were skeptical about LiDAR just like everyone else, but after trying mobile mapping, the accuracy and precision blew us away. We quickly recognized the potential and started adding tools to our toolbox.
Improved data acquisition and processing capabilities create pressure for surveyors to provide incremental data and feed the engineers data along the way so they can start work sooner. 3D laser scanning, in conjunction with conventional land survey, allows us to meet that demand. Instead of waiting until the end of the survey, we produce a preliminary surface model for the engineers that looks like a conventional land survey.
The preliminary model is so good they can complete most of their design work without waiting for the final deliverable. Laser scanning allows the engineer and surveyor to work in tandem throughout the lifecycle of the project, which shortens the overall project timeline.
Q. What tools, both hardware and software, does CEC use to meet these expectations?
When we started to experiment with LiDAR, we compared the results to conventional techniques to make sure we were maintaining high quality, and we were impressed with the results. In 2013, we invested in our own mobile mapping system, the Trimble MX9, as well as static-based terrestrial LiDAR. In 2016 we purchased a UAS with a LiDAR payload. CEC was one of the first firms to receive a Section 333 waiver from the FAA for commercial use of a UAS. We also contracted for aerial LiDAR acquisition from other providers, and in 2021 we acquired our own unmanned boat with subsurface mapping capability for bathymetric surveys.
CEC mounted a Trimble MX9 on a vehicle to capture laser scans and images.
Most hardware comes with proprietary software, so we have many software packages and use a lot of server space to store large volumes of data. Trimble® Business Center and TopoDOT are the primary software packages we use to handle large datasets. Once we have generated the point cloud, we do feature extraction in Trimble Business Center or TopoDOT, then move files into an Autodesk Civil 3D or MicroStation format, depending on the customer’s requirements.
Q. What are the benefits of using data fusion in surveying?
No technology is perfect for every situation. There are always obscured areas, like behind a wall or under heavy vegetation, so aerial LiDAR or mobile mapping needs to be supplemented with conventional land surveying. LiDAR can’t map a property line or underground utilities, so we combine it with GIS datasets to create a comprehensive survey. Combining data from multiple sources and using them together yields a better result.
Q. What parts of the workflow are impacted by integrating new technology?
The workflow is positively impacted by increased safety and reduced time in the field. Compared to 10 years ago, laser scanning has flipped the field and office time requirements. Using advanced technology, we collect a large volume of data in a day and generate and produce final deliverables from that data over multiple days. Instead of surveyors spending weeks collecting data for a topographic map, they can focus on other services, like pavement assessments and line sag analysis.
Oklahoma State Highway 10 posed unique surveying challenges.
Q. Talk about the project requirements and deliverables for the Transportation Design-Grade Survey project in Cherokee County, OK, conducted in the summer of 2019.
Oklahoma State Highway 10 was one of the more challenging roadway projects we’ve worked on. The 11-mile, 2-lane winding highway has numerous blind curves and no shoulders. A river runs along one side of the road, with a sheer rock face and overhangs along the other. Dense vegetation makes access difficult, and GPS-denied areas complicate data collection.
The highway had numerous sheer rock faces, overhangs, and blind curves.
Our deliverable was a transportation design survey for a cable barrier safety improvement project. Our field crews worked for 2-3 days to establish a control network for aerial and mobile LiDAR, plus one day to take check shots. To allow for the GPS-denied areas, we shortened the typical distance between GCPs to supplement GPS and took more check shots than normal. We wanted to be sure to validate the data up front to get useful and accurate deliverables at the end.
It took just one day to collect mobile LiDAR for both lanes with no traffic stoppage necessary. UAS LiDAR data collection was completed in two days. We broke the highway into 2-mile stretches to meet the FAA’s UAS Visual-Line-of-Sight requirements. Back in the office, the data was imported to Trimble Business Center and the final survey was produced in 2 1⁄2 weeks.
Mobile, terrestrial and aerial data were loaded into Trimble Business Center to produce the final deliverables.
Q. What Trimble hardware and software were deployed on this project?
We’re a Trimble house, so almost everything we use in the field is Trimble, including GNSS receivers, Trimble SX10 scanning total stations, and the Trimble MX9 mobile mapping system. Trimble hardware and software is integrated, which streamlines the workflow and allows us to work with LiDAR in the same ecosystem as conventional survey data. Trimble Business Center handles large volumes of data and acts as a data hub.
Q. What are the specific benefits of mobile mapping and what project characteristics are most suitable for mobile mapping?
We often work around highways and busy intersections that are dangerous for surveyors. If we can do 95% of data collection with a mobile mapper on a moving vehicle, the improved safety alone makes it worth investing in the technology, with the added benefit of tremendous detail in the data.
Mobile mapping-captured data offers a high level of accuracy.
Mobile mapping offers advantages on many types of projects. For any highway project longer than 10 miles or where there is heavy traffic, using mobile LiDAR saves time and improves safety. If a survey requires a high level of detail, like a downtown area with curbs, ADA ramps, etc., mobile mapping is faster than conventional surveying and captures everything.
We find mobile mapping particularly effective when data analysis of asset conditions is required. We’ve done over 1,000 miles of pavement analysis to help DOTs prioritize funding for maintenance. And mobile mapping is perfect for airport runways—instead of shutting down the runway and disrupting traffic, it only takes a few minutes to scan with the Trimble MX9.
Q. Would you recommend 3D laser scanning and data fusion be applied to other kinds of survey initiatives, and why?
Yes, without a doubt. New technology is intimidating, and cost can be a barrier to entry; however, we see the benefits on almost all projects. The hardware is faster and more efficient, and all survey work is improved by comprehensive LiDAR data. 3D laser scanning expanded our capabilities to offer new services, such as pavement analysis and dam change analysis, in addition to mobilizing on standard survey projects to improve the deliverables.
Q. What are the key takeaways from incorporating data fusion into your surveys?
We always want to use the right tool in the toolbox—it’s not a case where LiDAR replaces everything else. Laser scanning provides more data and more detail and billions of LiDAR points that allow us to model existing features exactly as they exist, not just generated from hundreds of survey shots. Combining this with other data sources completes the picture. The result is representative of the real world and supports a wide range of analysis.