Boasting over 1.9 million square feet of warehouse space and 100,000+ square feet of retail development, The Crossings, a massive mixed-use development site located in Burlington, New Jersey, was understandably no small feat to build. The initial proposal, a joint effort between MRP Industrial and Clarion Partners, two prominent mid- and north-atlantic real estate organizations, called for roughly 240 acres of land to be developed, to fit a host of uses including distribution centers, loading stalls, parking lots, and additional landscaping.
With so much at stake, and a tight deadline to finish it all, Cambridge Constructors & Engineers, a regional general contractor based out of Turnersville, set to work on the 160-acre warehouse site – utilizing a large volume of trucks, heavy machinery, and cross-functional construction crews to execute detailed engineering plans.
But as the site progressed, project managers encountered challenges in verifying intricate earthwork calculations across the entire site. They realized that traditional methods of manual surveying were insufficient for the task, yet onsite survey and engineering crews were too preoccupied with other urgent matters. To remedy the situation, Cambridge Constructors & Engineers reached out to The Drone Life for a prompt, accurate, and comprehensive LiDAR drone scan, along with an accompanying orthomosaic map.
Table of Contents
The Case for Drone LiDAR
Upon arriving on-site, The Drone Life’s first course of action was laying various ground control points (GCPS) across the planned flight area. For any surveying project, GCPs represent a crucial first step in ensuring accuracy and validity later. These scattered tiles connect the drone data with verifiable GPS coordinates, allowing individuals to locate precise regions in-map and match them to real-world areas on the site. Next, The Drone Life’s skilled pilots created a flight plan and flew the project site in one hour. From deployment (including uploading the LiDAR data, aligning additional GCPs, and processing time) to final deliverables sent, this whole process took 24 hours. All information was ready to send to Cambridge Constructors & Engineers the very next morning.
“You can’t shut a job down for three days while you survey – it just doesn’t happen. You have to weigh your options carefully.”
- Josh Seehousz, GPS Equipment Manager, Cambridge Constructors & Engineers
Clearly, this is in stark contrast to a fully-manual operation. Because engineers were in the middle of a cut and a fill balance, surveying on-foot would have presented its own set of challenges. The cut and fill balance entailed moving earth from various parts of the site to create the necessary elevation for building construction, but in its current state, was completely unwalkable, featuring a hazardous slope.
Aerial photo of The Crossings, a 1.9 million+ square foot industrial park. Located in Burlington, New Jersey
To attempt to physically survey this property using a 50/50 grid method with a standard two-man crew likely would’ve taken 3-4 unrecoverable business days. This doesn’t even take into account the fact that all work on-site would have to be stopped, affecting hundreds of individual jobs and contributors, and further delaying project progress. On a project of this size, conducting a physical survey would never be economically or physically feasible. Drone technology, and specifically LiDAR, was truly the only way to save time and money by keeping workers on-task and uninterrupted.
What's included in YOUR GUIDE...
A Proven Roadmap of Success for Implementing Drones in Construction.
A List of Red Flags to Avoid When Hiring Drone Service Providers.
How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
Josh Seehousz (Left) measuring a drone GCP target with a GNSS receiver
A Manual vs. Drone Survey Comparison
Drone LiDAR aims to provide a comprehensive, intricate dataset through powerful light detection and radar sensors, which measure distance on the ground fully remotely. This information can then be used to create 3D models, digital twins, and more interactive imagery. Armed with this information, Josh Seehousz, GPS Equipment Manager, compared The Drone Life’s LiDAR contours (or, what is commonly referred to as a point cloud) to manually-shot contours created shortly after ground-break by his team in AGTEK software.
Related Article – The Role of Drones for Construction Photo Documentation
“I’m a big advocate for drone LiDAR. A survey is a necessary evil – if it’s not possible to do manually within the time frame that you have, you have to look elsewhere.”
- Josh Seehousz, GPS Equipment Manager, Cambridge Constructors & Engineers
What took The Drone Life roughly half a day end-to-end saved Cambridge Constructors & Engineers thousands in labor costs. Assuming a $97 hourly rate for a field survey crew, and a $75 hourly rate for office team members’ processing time.
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LiDAR drone contours of the construction site
Mistaken Plans, Missing Earth, & Incorrect Grade
What Josh and his team discovered was a critical piece of missing earthworks data. Specifically, over 100,000 cubic yards of material! After investigating further, the team realized that a large pile of dirt was delivered before the cut and fill balance began. As the ground surrounding it was built up, the stockpile actually went ten to fifteen feet below the grade around it. When the general contractor originally shot the site, they chose to only take ground measurements – missing the dirt below.
“You’re only as good as the data you’re given. If you’re given missing or inaccurate data to start with, the entire project is set up to fail.”
- Josh Seehousz, GPS Equipment Manager, Cambridge Constructors & Engineers
While it’s impossible to determine any one reason for the miscalculation, it’s clear that the consequences could have been even worse if the error was not independently verified. After discovering this mistake, Cambridge Constructors & Engineers had to replace the soil needed to fix the grade in another way, as it was missing from the jobsite, yet was budgeted to be from within. Josh explained the company’s three options to us:
- Importing and/or buying the dirt
- Changing project plans completely
- Digging the site’s stormwater basins deeper, freeing up extra material
Regardless of choice, paying for the labor, expenses, and change orders is a costly undertaking that should be avoided whenever possible. Unfortunately, this was necessary to ensure the completion of the project.
But for roughly one-tenth of the cost, The Drone Life team eliminated additional trips, manual surveys, and purchases, by verifying the exact amount of missing material.
Conclusion: Reducing Man-hours & Unforeseen Costs
Due in part because workers remained active on-site while the drone survey was performed from above, Cambridge Constructors & Engineers’ project was able to remain efficient and on-track for completion despite this earthworks discrepancy. With enough time to fix these issues, the company proactively solved this problem in a low-cost, reliable way, with the help of LiDAR technology and The Drone Life’s drone pilots. In our interview, Josh told us that The Drone Life’s maps were both very accurate and what the team expected – the scan was just as good as the team’s original physical survey. Near the end of the project, the photogrammetry became a “checks and balances” of sorts for the team, allowing for elevation spot checks and simple validation.
For the wealth of information and aerial coverage one receives, drone surveys are well worth their cost. In the long run, and as Josh described, this is often a less expensive alternative to manual surveying. At The Drone Life, our team of experts offer 1:1 consulting and tailored aerial service solutions for your construction project or organization. With over five years of direct experience in the AEC industry, we can assist on everything from site surveying to mapping to progress documentation.
If you’re interested in learning more about LiDAR drone mapping, schedule a free consultation with one of our drone experts.
What's included in YOUR GUIDE...
A Proven Roadmap of Success for Implementing Drones in Construction.
A List of Red Flags to Avoid When Hiring Drone Service Providers.
How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
