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Drones Advance Land Survey Capabilities

Aerial drone imagery of U.S. 151 near Anamosa was used to complement traditional survey methods.

Survey technology is soaring to new heights with the addition of unmanned aerial vehicle (UAV) or drone as more commonly known. When fitted with GPS technology and a high-resolution camera, these drones are often referred to as unmanned aerial systems (UAS). These remotely flown aircraft, equipped with a full package of software and hardware, offer a new approach to construction progress, observation, and monitoring, including photos and video, and traffic studies.

In the land survey field, drones add an entirely new dimension for their ability to provide aerial photogrammetry, 3D site modeling, photo comparisons, and aerial video.

An orthomosaic image of U.S. 151 was used to create a 3D model of the project site.

They’ve even shown their value in determining stockpile or basin area/volumes and infrastructure inspections. With a forward-looking approach to land survey and civil engineering design, the Snyder & Associates team is excited to provide their clients with a deeper bench of solutions, using the eyes in the sky their drones provides.

“All of the service offerings we provide will benefit from this technology and the data a UAV provides,” shares Snyder & Associates Surveyor Ted Jansen. “We’re able to swap different cameras, thermal imaging units, and other components to provide different project efficiencies for our clients.”

Determining Which Project Types Benefit from a Drone Survey

Every survey project begins with a discussion of the overall project needs to determine how the survey fits into the big picture and what survey methods are applicable. Site accessibility, constraints, and project limits are important factors in determining if an aerial flight is appropriate. Here are some common questions that help determine if an aerial survey would be beneficial.

  • What surrounds the project site?
  • What are the ground cover conditions?
  • What deliverables are needed, and when are they needed?

Every project is different, and not all sites are accessible for aerial services. Realistic expectations need to be made, taking timing and weather into account. If the ground can’t be seen from the sky, the accuracy of an aerial survey is diminished. Project sites within five miles of certain airports require FAA authorization before an aerial flight can occur, which typically takes between two days and two weeks to receive approval. Evaluating the wide range of factors that influence site accessibility, along with your project needs and goals, helps maximize the use of resources and project funds.

Operating a Drone for Land Survey 

Visual depiction of an autonomous flight program in progress during work on Iowa U.S. 75 near Sioux Center. The 3D modeling of the project corridor was instrumental in providing citizens a first-hand view of the proposed project details before construction began.

The UAV can be flown manually or fully autonomous with manual backup. A fully autonomous flight follows a predetermined plan designed by the flight team. During an autonomous flight, data is collected and processed using cloud-based processing software that transmits back to a tablet. An FAA Part 107 certified UAS pilot monitors the flight from the ground to ensure safe UAV operation.

Existing topographic features of the site determine the altitude of the flight and the altitude determines the image resolution. As altitude increases, resolution deteriorates, so image clarity and the accuracy of the surface data diminishes. On the other hand, higher altitudes decrease survey flight time and data file size, decreasing costs and allowing a more efficient file size. The maximum altitude that a commercial UAS is typically allowed to fly is 400 feet above ground level (AGL).

While it’s usually a breeze to fly a UAV and gather data, there’s more that goes on behind the scenes to make that data usable. A UAV simply provides a point cloud that includes georeferenced coordinates and elevations at many locations to create a surface. Design Technicians analyze and process the data the UAV provides to create the desired deliverables.

Best Projects for Drone Use

Drones can assist with a variety of civil engineering projects. However, there are specific instances where a drone may be recommended:

  • Safety — rough terrain, heights, and other circumstances that pose safety risks to survey and engineering staff
  • Level of Detail — UAVs can be flown at low altitudes to gather high-resolution data that rivals traditional survey methods
  • Project Planning, Progress, & Closeout — UAVs can help capture existing site data that’s valuable in assisting with land planning and phasing. In addition, as the project progresses, a UAV can be used to track project milestones and provide aerial images of the end result

Can a Drone Survey Replace a Traditional Survey?

A UAS will not eliminate the need for surveyors on the ground or traditional survey methods. Rather, it’s designed to enhance current survey methods by offering higher detail and better coverage of the information gathered. In utilizing the UAS, Ted and his colleagues have determined that it increases the amount of usable data available for design while reducing time in the field, increasing the team’s efficiency.

In terms of accuracy, the horizontal and vertical error of the UAS cannot be less than the site control points, and the method that these control points are obtained. Control point placement on the project site, logging, and processes will determine the overall accuracy of the flight survey. Boundary surveys, underground utility surveys, bathymetric surveys, along with the need to verify and check aerial survey data will always be required and remain a common practice.

Using UAS Technology on Your Next Project

Snyder & Associates provides comprehensive services and utilizes a variety of cutting-edge technologies to gather data efficiently and accurately. Whether you have environmental disturbance or site access concerns, or would just like to get a bird’s eye view of site topography, UAS can be beneficial. To learn more about Snyder & Associates UAS program and explore opportunities for UAS technology on your next project, contact Eric Miller.

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