What is meant by drone survey?
A drone survey refers to the use of a drone, or unmanned aerial vehicle (UAV), to capture aerial data with downward-facing sensors, such as RGB or multispectral cameras, and LIDAR payloads. During a drone survey with an RGB camera, the ground is photographed several times from different angles, and each image is tagged with coordinates
Photogrammetry combines images that contain the same point on the ground from multiple vantage points to yield detailed 2D and 3D maps.
From this data, a photogrammetry software can create geo-referenced orthomosaics, elevation models or 3D models of the project area. These maps can also be used to extract information such as highly-accurate distances or volumetric measurements.
Unlike manned aircraft or satellite imagery, drones can fly at a much lower altitude, making the generation of high-resolution, high-accuracy data, much faster, less expensive and independent of atmospheric conditions such as cloud cover.
All You Need To Know About Drone Surveying
Drones are continually proving to be powerful commercial tools, simultaneously providing adopters with leaps in efficiency and safety. The surveying and mapping industry is no exception.
With their ability to capture data from above, drones have been successfully integrated into surveying workflows to perform land surveys, photogrammetry, 3D mapping, topographic surveying, and more.
Whether you’re an experienced surveyor looking to expand your toolkit, or you’re a drone enthusiast who wants to know more ways to use their drone, or you’re just generally interested in this awesome application of drones, we’ve put together an article to help you learn everything you need to know when it comes to getting started with drone surveying.
Benefits of drones in surveying
Reduce field time and survey costs
Capturing topographic data with a drone is up to five times faster than with land-based methods and requires less manpower. With PPK geo-tagging, you also save time, as placing numerous GCPs is no longer necessary. You ultimately deliver your survey results faster and at a lower cost.
Provide accurate and exhaustive data
Total stations only measure individual points. One drone flight produces thousands of measurements, which can be represented in different formats (orthomosaic, point cloud, DTM, DSM, contour lines, etc). Each pixel of the produced map or point of the 3D model contains 3D geo-data.
Map otherwise inaccessible areas
An aerial mapping drone can take off and fly almost anywhere. You are no longer limited by unreachable areas, unsafe steep slopes or harsh terrain unsuitable for traditional measuring tools. You do not need to close down highways or train tracks. In fact, you can capture data during operation without an organizational overhead.
How accurate are drone surveys?
Before adopting drones into their workflows, many surveyors ask about aerial surveying accuracy. What degree of accuracy can drone surveying techniques achieve?
Surveying drone solutions can produce surveys with different degrees of accuracy, depending on the requirements of the project.
In an independent study by DroneDeploy, the DJI Phantom 4 RTK achieved 2 cm relative vertical accuracy and 1.20 cm relative horizontal accuracy.
For some applications, like checking crop growth, or construction progress, high relative accuracy is sufficient. For other jobs that also require high absolute accuracy, there are drones equipped with real-time kinematics (RTK) and post-processing kinematics (PPK) capabilities. When paired with a few GCPs, survey-level accuracy can be achieved.
How to process drone survey data?
While surveying with drones, images of the ground are taken from multiple vantage points. Through processing these images, a photogrammetry software can then create orthomosaics and 3D models, from which it can measure accurate distance, as well as surfaces and volumes of physical objects.
Data outputs from the drone
Images taken by the drone are usually saved on a memory card (such as SD card), just like for any other camera. Depending on the technology used by the drone, the images are already geo-tagged or can be imported in a geo-tagging software, such as WingtraHub. According to the size of the survey site, you probably have between a few hundred images and a few thousand, and each image contains geographical information (X, Y, Z).
Importing into a photogrammetry software
After importing or uploading the geo-tagged images in a photogrammetry software such as Drondeploy, delair.ai, 3DR Sitescan or Pix4D, images will be stitched together to create 2D or 3D models of the surveyed site. Image processing can be a lengthy process depending on the number of images and the performance of your computer. Some photogrammetry software are desktop-based, thus requiring robust hardware. Other software is cloud-based, employing powerful servers instead of your local computer to process the data.