Surveying with a drone
Surveying & GIS
Surveying with a drone offers enormous potential to GIS professionals. With a drone, it is possible to carry out topographic surveys of the same quality as the highly accurate measurements collected by traditional methods, but in a fraction of the time. This substantially reduces the cost of a site survey and the workload of specialists in the field.
Orthomosaic and digital surface model created from aerial images taken by the WingtraOne surveying and mapping drone.
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This comprehensive e-book covers all the benefits of using drones, from reducing costs and field workload to enabling large topographic surveys with high accuracy requirements.
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.
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.
What are the 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
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.
What are drones used for in surveying?
Land surveying / cartography
Survey drones generate high-resolution orthomosaics and detailed 3D models of areas where low-quality, outdated or even no data, are available. They thus enable high-accuracy cadastral maps to be produced quickly and easily, even in complex or difficult to access environments. Surveyors can also extract features from the images, such as signs, curbs, road markers, fire hydrants and drains.
Land management and development
Aerial images taken by drones greatly accelerate and simplify topographic surveys for land management and planning. This holds true for site scouting, allotment planning and design, as well as final construction of roads, buildings and utilities.
These images also provide the foundation for detailed models of site topography for pre-construction engineering studies. The generated data can also be transferred to any CAD or BIM software so that engineers can immediately start working from a 3D model.
As data collection by drones is easily repeatable at low cost, images can be taken at regular intervals and overlaid on the original blueprints to assess whether the construction work is moving according to plan specifications.
Precise measurements
High resolution orthophotos enable surveyors to perform highly-accurate distance and surface measurements.
Stockpile volumetric measurements
With 3D mapping software, it is also possible to obtain volumetric measurements from the very same images. This fast and inexpensive method of volume measurement is particularly useful to calculate stocks in mines and quarries for inventory or monitoring purposes.
With a drone, surveyors can capture many more topographic data points, hence more accurate volume measurements. They can also do this in a much safer way than if they had to manually capture the data by going up and down a stockpile. Since drones are capturing the data from above, operations on site won’t be interrupted. The short acquisition time enables capturing a site snapshot at a specific point in time.
Slope monitoring
With automated GIS analysis, it is possible to extract slope measurements from DTMs and DSMs generated by drone imagery. Knowing the steepness of the ground’s surface, the areas can be classified and used for slope monitoring purposes, including landslide mitigation and prevention.
With orthomosaics taken at different times, it is possible to detect changes in earth movement and to measure its velocity. This data can help predict landslides and prevent potential damage to roads, railways and bridges.
Urban planning
The development of increasingly dense and complex urban areas requires intensive planning and therefore time-consuming and expensive data collection. Thanks to drones, urban planners can collect large amounts of up-to-date data in a short period of time and with far less staff. The images produced in this way allow planners to examine the existing social and environmental conditions of the sites and consider the impact of different scenarios.
Thanks to 3D models, buildings can also be easily overlayed onto their environment, giving planners and citizens an experimental perspective of a complex development project. 3D models also allow analysis and visualization of cast shadows and outlooks/views.
Maps produced with a WingtraOne drone and Esri’s ArcGIS Urban.
What kinds of deliverables can you expect with drone surveying?
It depends on the camera or sensor and the software you are using for post-processing. RGB mapping cameras like the Sony’s RX1R II or a6100 together with most photogrammetry software can produce the following data:
Orthomosaic maps
Drone images are corrected for image distortion and stitched together during post-processing to create a highly-accurate orthomosaic map. Each pixel contains 2D geo-information (X, Y) and can directly procure accurate measurements, such as horizontal distances and surfaces.
File formats: geoTIFF (.tiff), .jpg, .png, Google tiles (.kml, .html)
3D point cloud
Digital surface models (DSM)
Drone images can also be used to create DSM models of the area. Each pixel contains 2D information (X, Y) and the altitude (Z value) of the highest point for this position.
File formats: GeoTiff (.tif), .xyz, .las, .laz
Digital terrain model (DTM)
File formats: GeoTiff (.tif)
3D textured mesh
The 3D textured mesh is a reproduction of the edges, faces, vertices and texture of the area shot by the drone. This model is most useful for visual inspection or for when external stakeholders or public involvement is essential for a project.
File formats: .ply, .fbx, .dxf, .obj, .pdf
Contour lines
File formats: .shp, .dxf, .pdf
How accurate is a drone survey?
The performance and type of drone, the quality of its components, the camera resolution, the height at which the drone flies, the vegetation, and the method and technology used to geolocate the aerial images can heavily influence the accuracy of drone survey mapping. At this point, it is possible to reach an absolute accuracy down to 1 cm (0.4 in) and 0.7 cm/px (0.3 in/px) GSD under optimal conditions with a high-end surveying drone such as the WingtraOne.
What are the best drones for surveying?
WingtraOne mapping drone
Large surveying areas, difficult or steep terrain, great altitude differences, harsh weather conditions or the absence of flat surfaces required for take-off and landing: the WingtraOne mapping drone can overcome all these challenges of surveying mid- and large-scale projects.
Take off and land vertically (VTOL)
Eliminate dangerous belly landings, hand launches and catapults. Unlike other fixed-wing drones, the WingtraOne takes off and lands smoothly in confined areas, on gravel, between tree stands or in mountainous areas.
42 Megapixels / 0.7 cm/px (0.3 in/px) GSD
With its full-frame 42 MP Sony camera, the WingtraOne can fly at high altitudes while still providing low GSD images. This guarantees that large areas can be surveyed faster with high accuracy. Higher resolution also yields better orthomosaic map reconstruction.
Down to 1 cm (0.4 in) absolute accuracy
Using the PPK option, it is possible to reach down to 1 cm (0.4 in) absolute accuracy, previously only feasible with ground-based survey equipment. This requires optimal conditions, flight above hard surfaces and the use of well-marked, highly-visible, manually-measured checkpoints and a well-established based station.
Other drones for surveying and mapping
In the end, the best drone for your land surveying project depends on many factors, such as the size of the survey site, desired output quality, and your budget and preferences. For more details on how to make this decision, read our photogrammetry drone comparisons: WingtraOne vs. DJI Phantom 4 RTK, WingtraOne vs. eBee X and WingtraOne vs. Quantix.
How to do a drone survey?
1. Check before you leave the office
Check the local regulations and make sure that you are allowed to fly your drone at the planned location. Also, make sure that the weather is suitable, meaning no rain, fog, snowfall or strong winds. Check that the battery of your drone and connected devices such as tablets are fully charged and that the memory card of your drone camera has sufficient empty space to capture the entire project.
2. Plan your flight
You can create the survey flight plan with the drone flight planning app on the tablet. For this, just tap and drag the points around the area you want to survey, or import a KML file. Make sure you account for tall objects within the flight plan, as well as altitude differences. If needed, you can adjust flight settings such as altitude, ground sampling distance (GSD), flight direction and images overlap.
3. Set up your flight in the field
During this step, you basically unpack and assemble the drone and make sure that it is ready to take-off in safe conditions. Following the interactive check-list, you will one-by-one check every parameter, like cleaning the distance sensor and making sure the camera lid is removed.
4. Fly and collect images
After pushing the take-off button, the drone autonomously takes off, captures images and lands back where it started. In this step, the operator essentially makes sure that nobody approaches the drone during take-off or landing and that the weather conditions stay optimal for the survey mission.
5. Geotag your images
After one or several flights, import the images into WingtraHub software to geotag them s. Geo-tagging assigns geographical position (X, Y, Z) information to the images either in a separate CSV file or in the images’ meta-data.
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 Propeller, Bentley ContextCapture 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.
What is the difference between lidar and photogrammetry?
Since some aerial survey drones can now carry LIDAR sensors, what is the right choice between a LIDAR and a photogrammetry payload? It all depends on the specific use. Find out how these two technologies work, their features, and the most suitable for your project: Drone lidar vs. photogrammetry.
