Friday, January 26, 2018

Photogrammetry offers easy, accurate solutions for owners and trade partners

A site capture of Firestone in Opelika, Ala., offers measurements at 1-inch accuracy through use of survey control points.

Construction of the Firestone store in Opelika, Ala., required a series of cut and fills before construction began. Wanting to ensure that the site’s grade was maintained and that stormwater drainage requirements were achieved, the EMJ Special Projects team enlisted the help of Caleb Wickersham, Virtual Construction Engineer and licensed drone operator.
Using GPS coordinates and other data, Caleb conducted programmed, automated flights along the same path at each stage of the site’s preparation. During the flights, the drone captured high-resolution images of the site from which Caleb applied photogrammetry.
“Photogrammetry offers construction teams the ability to capture measurements and record the site how it was at the time of flight,” said Caleb.

The measurements obtained through this process are within an inch of accuracy and offer endless applications in the construction industry.

“It allows us to go back if something goes wrong and see where and when the problem occurred or can be used to hold project participants accountable for their contracted responsibilities,” said Caleb. “Taking measurements can also offer data that would otherwise take extra time, effort and money to obtain. For example, after a drone flight at the Hampton Inn site in Decatur, Ga., we captured the height of surrounding buildings. This was then used to discuss crane logistics and security camera locations for the site.”

At EMJ Construction’s Ruby Falls project in Chattanooga, Tenn., the team requested Caleb’s help in determining the amount and estimated cost of concrete.
“It allowed the project team to see how much concrete would be needed to fill the space between a wall and cliff face and make decisions based upon that volume estimate,” said Caleb.

This photogrammetric 3D model was used for confirming measurements at Ruby Falls. Green photo projections represent where the photos were taken in 3D space.

Drone flights cost roughly $500 per flight, but the cost can vary based on the number of flights and the job site location. Teams receive their drone deliverable package typically within 48 hours of the drone flight, and Caleb and his team can provide them anything from an orthomosaic sitemap (a top down view of site at high resolution) and volumetric calculations to 360 photos and video.

“Additionally, EMJ clients are able to see the data as we capture it,” said Caleb. “This allows them to see a timeline of the building as it rises from the ground and assists in communicating progress. Subcontractors also benefit from the data and the availability of an active, up-to-date map of the site as they develop their execution plans.”

For more information on photogrammetry or to enlist the Construction Technology team’s help with a project, contact
Caleb Wickersham joined EMJ Corporation in 2017 and is focusing on building EMJ’s field technology capabilities, such as drones, Matterport and laser scanning, as well as assisting with BIM coordination and other related tasks.