AERIAL MAPPING AND SURVEY BY DRONE

Aerial Mapping and Survey with the latest technology like drone offers enormous potential to GIS and architects 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 like total station or DGPS, 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 models created from aerial images taken by the Atom surveying and mapping drone.

What is meant by drone survey?
What are the benefits of drones in surveying?
What are drones used for in surveying?
What kinds of deliverables can you expect with drone surveying?
How accurate is a drone survey?
What are the best drones for surveying?
How to do a drone survey?
How to process drone survey data?
What is the difference between lidar and photogrammetry?

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

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.

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.

After post-processing with a photogrammetry software, these same images can produce very detailed elevation models, contour lines and breaklines, as well as 3D reconstructions of land sites or buildings.

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.

Compared to traditional monitoring techniques, where sensors are placed on single points, drones enable more comprehensive data collection. Drones with PPK capability, which do not require laying out of multiple GCPs, are optimal for this application, since these areas are often hard to reach or even dangerous.

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 QX1 together with most photogrammetry software can produce the following data:

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.

How to do a drone survey?

Learn how to conduct a drone survey with WingtraOne in this video. You will see how to plan a flight, how to collect aerial images and how to safely interact with the drone at any time. Watch how orthomosaic maps, point clouds and digital elevation models are produced from the collected images.

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 the calibration of the airspeed 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. 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, 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 an 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 into 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 is 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.

Atom Aviation Services is an ISO-certified aviation company that deals with the best drone survey company in India and multiple aspects of aviation across various parts of the World. The company was founded by a young aspiring pilot after years of dedication and experience in aviation.