Surveying Drones: How to Use Drones for Surveying
*** Article Sourced from Vision Aerial ***
***We are not licensed surveyors with the State of Ohio***
Many GIS professionals conduct land surveys on the ground with specialized tools like GPS rovers and base stations. This process is time-consuming, inefficient, and sometimes even dangerous. Surveying drones, or autonomous aerial vehicles (UAVs), perform the same kinds of surveys in a fraction of the time while keeping personnel safe. The data collected produces highly accurate topographic surveys that cost significantly less than ones collected with traditional methods.
What are Survey Drones and Aerial Surveys?
Surveying drones are unmanned aerial vehicles that fly over a defined area with sensors pointing toward the earth. They collect high-resolution images and geographic coordinates wi
th professional cameras, LiDAR, or other kinds of sensors. Typically, the drone flies over the area in a predefined survey pattern, taking overlapping photos at intervals from several angles.
After the drone survey flight, the images and geo data collected go through post-processing. Specialized software converts the images and data into orthomosaic maps, digital terrain models, 3-D models, and other specialized outputs. The final deliverables can then be analyzed to determine distances, angles, measurements, volumes, and other critical information.
How Aerial Drone Surveys are Used
Just as with traditional surveying, drone surveys have a wide range of applications. Typical land surveys establish boundaries, define lines, capture historical evidence, and create records for lega
l documents like deeds. Construction surveys determine where a highway, structure, or building will be located. Surveyors can also collect data to define how land needs to be graded before construction begins. Additionally, land-use agencies can conduct environmental impact studies when choosing the site.
Some Typical Uses for Drone Surveys
Urban planning and development
Construction and planning
Environmental studies and research
A surveying drone can gather the data needed to produce orthomosaics, 3-D models, or cadastral maps. The detail collected in the images is then used by surveyors to establish boundaries, define lines, generate maps, or provide other kinds of detailed geographic data for their clients.
Urban Planning & Development
GIS data, 3D surveys, and orthographic maps are a necessity for urban planning. From a bird’s eye view, planners can see how to best use and develop their area. They can assess the impact of new construction, or discover how a new road will change the landscape. Finally, the systematic collection of data with a survey drone aids in providing information critical to the success of engineering and infrastructure projects.
Drone surveys combined with modern construction techniques offer incredible benefits. The majority of survey drones in the construction industry assist in aerial planning, inventory management, topographic mapping, 3D reconstruction of sites, and monitoring construction projects. Project managers and engineers can also use the data collected from aerial surveys to control quality. Furthermore, modern excavation equipment can use 3D data products, GPS, and project data to autonomously perform their grading tasks.
In addition to measuring boundaries, drones can collect data for environmental surveys. These kinds of surveys determine what kinds of plants, animals, or other natural features are in an area. They can also measure how these items change over time.
Multispectral sensors allow scientists to measure aspects of plant health by looking at chlorophyll levels and other indicators. These sensors can also help scientists determine plant density and variety.
Mining & Aggregates
There are a variety of uses for drone surveys in the mining industry. Orthomosaics can be used to look at changes in slopes, for planning haul roads, watch tailings ponds for signs of runoff, and for incredibly accurate volumetric measurements of stockpiles.
Drone surveys accurately measure stockpile volumes. Survey drones are used in the mining and construction industries for planning haul roads.
What Kinds of Data Do Survey Drones Produce?
During an aerial survey, drones collect images and geo-location data. Then, post-processing software combines the images and geo data to produce the following types of items:
3D Point Clouds
3D Textured Mesh
Digital Surface Models (DSM)
Digital Terrain Models (DTM)
What is Photogrammetry?
Photogrammetry is the science of using images for measurements and includes extracting 3D information from photos. The process starts by taking overlapping photographs with a survey drone. Then, the images are converted into 2D or 3D digital models. Surveyors, architects, engineers, and contractors use photogrammetry to create topographic maps, point clouds, or drawings.
What is Photogrammetry Post-Processing Software?
Images and location data collected from a surveying drone need to be processed to create a final output as mentioned above. The software uses the data to stitch the images together with the additional data. It can calculate measurements between objects or determine angles. There are also tools that can determine the volume of materials piled on the ground to produce volumetric measurements.
Examples of commonly used post-processing software:
Pix4D – 3D ortho mosaics, 3D point clouds, digital surface models, contour lines, 3D textured models, and volumetric calculations
RDOAI – 3D ortho mosaics, 3D point clouds, digital surface models, contour lines, 3D textured models and volumetric calculations
Agisoft – Digital elevation models, digital surface models, georeferenced orthomosaics, 3D models, panorama stitching, multispectral image processing, automatic powerline detection.
Autodesk ReCap Pro – Uses data from laser scans and photos to generate survey-grade 3D and 2D models, textured meshes, point clouds with geolocation, and high-resolution orthographic views with elevation maps.
DroneDeploy – 3D point clouds, volumetric analysis, multispectral image processing, digital surface models, digital terrain models, cut/fill elevation comparison,
RealityCapture – 3D models, 3D textured mesh, level of detail models, digital surface models, digital terrain models, digital maps
3DSurvey – Digital maps, 3D models, interactive measurements, digital surface models, volume calculations, 3D point clouds, contour lines, integrated CAD tools
Data in Pix4D software. Photogrammetry software stitches multiple images together.
How to Use Drone Survey Data
Orthomosaic maps take multiple high-resolution images and stitch them together to provide a detailed aerial view of an area. There are many uses for these kinds of images. A realtor or land developer reviews ortho mosaic maps to determine how a property is laid out, where the buildings are located, and how easements interact with the property. Construction managers use them to plan job sites, monitor construction progress, communicate with a client, or compare as-built to as-designed. Scientists and researchers conduct environmental studies with ortho mosaics. They use a drone survey to assess the current characteristics of an area, and then monitor changes over time. In agriculture, farmers use ortho mosaic maps to see how their crops are performing, how irrigation channels shift or capture annual records.
3D Point Clouds
Point clouds take all the georeferenced data points captured by a survey drone, and put them together in 3D space. This data can be used to create a 3D mesh or model for use with CAD or other Building Information Modeling software.
Point cloud rendered in Pix4D
3D Textured Mesh and 3D Models
A 3D point cloud can be converted into a 3D textured mesh or 3D model. There are a wide variety of uses for this kind of information. Construction managers can use 3D models to monitor construction projects. In public safety, investigators and forensic teams use 3D models to reconstruct scenes. Engineering firms create complex models for their development projects. Architects use them to show stakeholders how the finished project will look. In the film industry, artists create a 3D model of reality and then apply visual effects.
Digital Surface Models (DSM)
In addition to elevation changes, a digital surface model describes natural and man-made features on the surface of a landscape. DSMs are useful for urban planning. Professionals use these to see how a new structure or road will impact the surrounding landscape.
Digital surface model made in Pix4D.
Digital Terrain Models (DTM)
Similar to a DSM, a digital terrain model describes the surface of the landscape, minus any features like trees and buildings. They are also known as “bare-earth digital elevation models.” Changes in elevation are colorized so peaks, hills, mountains, valleys, and slopes are apparent. DTMs are useful for environmental planning, modeling water drainage, and analyzing physical geography.
An ortho-mosaic with contour lines describes elevation. Topographic maps tend to utilize contour lines. Each line indicates a relative change in elevation. In construction and mining, the software uses contour lines to represent the physical world. The contour lines can also assist with calculating the volume of a stockpile.
Contour lines produced by a drone survey.
What Are the Advantages of Using Surveying Drones?
70% of contractors believe that advanced technologies can increase productivity (78%), improve schedule (75%), and enhance safety (79%). USG + U.S. Chamber of Commerce
Survey Drones are Faster and Less Expensive
Surveyors sometimes have to lug awkward equipment over uneven terrain.
When compared to other kinds of methods, surveying drones are faster, less expensive, and produce better results. Using traditional methods, The amount of time it takes to survey a quarter-acre lot is approximately 2-4 hours. The amount of time it takes to survey a 3-acre lot on foot is approximately 6-8 hours. A drone survey of the same 3-acre lot takes about five minutes (depending on altitude, overlap, and camera specifications). Traditional surveys can take a lot of time if dense vegetation is present. However, vegetation would not impede a survey drone.
Airplane and Helicopter Surveys are Expensive
When compared to surveys conducted with airplanes and helicopters, drones produce better results at a lower cost. Drones fly slower than airplanes and helicopters and at lower altitudes.
Therefore, the images that survey drones collect are of higher resolution. (Learn more about Ground Sample Distance.) Higher-resolution images are of far greater detail which is necessary for survey-quality deliverables.
The cost of a helicopter or airplane survey is also significantly higher per hour than a drone survey. Typical rates for a helicopter and pilot are hundreds of dollars per hour. Drones take much less time to prepare and deploy. Vision Aerial drones for surveying are easily transported to the survey location and launched within two minutes. Quicker setup and deployment result in less time needed for the survey which also translates to lower costs.
Gopher holes are hazardous to surveyors!
Aerial Drone Surveys Improve Safety
Aerial surveys remove the need to traverse difficult terrain on foot. Surveyors no longer have to worry about gopher holes and heavy equipment. They don’t have to lug awkward total stations and rovers over rugged ground. All a surveyor has to do is pre-plan their flight, set up the surveying drone, and deploy the mission from a safe area. When the mission is complete, the drone autonomously returns to the launch location. The surveyor then packs it up and heads back to the office to process the images.
Surveying Drones are Incredibly Accurate
A survey drone with a high-resolution camera flying at low altitudes and speeds can achieve incredibly accurate results. Then you can feed the Aerial survey data into a variety of software programs to produce precise measurements, maps, and models. What’s more, the data is persistent, meaning you can leverage new technologies for years to come.