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CASE STUDY

High-Accuracy Construction Mapping With GCPs and Correlator3D


Bullseye Construction is a site contractor operating in the Southeast US managing all aspects of construction site work including survey and mapping with drones. Some form of survey is always required to ensure the drone-based map products are accurately tied to the ground. This can be in the form of targets surveyed near or within the project site, or using technologies such as RTK or PPK on the drone itself in conjunction with a receiver on the ground. In either case, the goal is to correct the position of the raw image data spatially so that it fits the same reference system on the ground.

High-Accuracy Construction Mapping with GCPs and Correlator3D
INDUSTRY

Construction


COUNTRY

United States


USE CASE

Leveraging RTK/PPK and GCPs for Construction Mapping 


CHALLENGES
  • Site access
  • Targets in an active construction site
  • Local coordinate systems
  • Consistency with recurring missions

 

BENEFITS
  • Rapid and repeatable acquisition
  • Redundancy in survey
  • Simple project setup
  • Accuracy validation
Bullseye Construction
CHRIS GREENE

“We almost always use a combination of direct georeferencing and surveyed targets on our projects. Inevitably you will lose targets to construction work on site, but the ability to import direct georeferenced images, and validate them in Correlator3D with any remaining targets really puts your mind at ease when high accuracy matters.”

CHRIS GREENE

UAS MANAGER WITH BULLSEYE CONSTRUCTION

High-Accuracy Construction Mapping with GCPs and Correlator3D

WORKFLOW


Chris and his team begin by surveying in a network of aerial ground control points (GCPs), ensuring they do not place them where potential earth work may interfere. To be safe, additional targets are put beyond the perimeter of the site as well. With a pre-determined flight plan, the drone captures the imagery along with direct georeferencing information using PPK. The imagery, positioning information from the PPK solution, and surveyed control are then brought into Correlator3D for processing.

A coordinate system ang geoid offset are added at project setup. If it is a local coordinate system, then additional steps are taken to shift the data so that they are consistent with the GCPs. Aerial triangulation is performed using the direct georeferencing method constraining the image orientations to the PPK results. Once this is complete, the GCPs are measured as check points and a bundle adjustment is performed. An accuracy report is produced showing the residuals between ground and the surveyed GCPs. If the PPK solution and checkpoints are within the desired accuracy the workflow continues, and deliverables are created. If not, checkpoints can be converted to GCPs and used to correct any issues.

DELIVERABLES

Typical deliverables consist of a high-resolution digital terrain model (DTM), a digital surface model (DSM) and an orthomosaic.

 

BENEFITS

The benefits of using Correlator3D according to Bullseye Construction are the ability to work with both GCPs and RTK/PPK solutions. If one has issues, the other can still be used to create highly accurate mapping products. Also, with these types of projects being visited multiple times per year, the ability to run automated workflows with scripting in Correlator3D is very beneficial.

 

ABOUT BULLSEYE CONSTRUCTION

Originating as a utility contractor in 2001, Bullseye Construction Inc. is now a full service, turnkey site contractor. Kevin Johnson, owner of Bullseye Construction Inc., continues to excel and set itself apart from its competitors through hard work, integrity, and expertise. Bullseye Construction Inc. is known for their honest and transparent negotiation and bidding process, knowledgeable and efficient project managers, and hard-working utility and grading crews. For more information, visit www.bullseyeconstructioninc.com.

High-Accuracy Construction Mapping with GCPs and Correlator3D

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