I’m sure you’ve already heard about drones. They’re powerful tools used in many industries today, providing a great deal of safety, efficiency, and accuracy to adopters. Drones are now also being utilized in land surveying. If you’re a land surveyor or interested in becoming one, it’s a must to know about using drones in mapping and evaluating plots of land.  Land surveyors integrate drone technology in their work to perform 3D mapping, photogrammetry, aerial surveying, topographic surveying, among other applications. For you to learn more about drone surveying, here’s a blog article that tells you what you need to know about this subject matter. 

What is a Drone Survey?

To better understand drone surveying, let’s first define what land surveying is. Land surveying is the science of determining or re-establishing boundaries, lines, corners, positions, distances, and monuments of real property or land.  A drone survey is the application of drones or unmanned aerial vehicles (UAV) to capture data or gather information to be used in land surveying. Drones with multispectral cameras, RGB cameras, and LiDAR payloads can photograph a survey site several times from different angles.  The data can then be utilized to create 3D models or geo-referenced orthomosaic maps of the project area using photogrammetry software. A land surveyor can get highly accurate volumetric measurements or distances from these maps.  Compared to satellite imagery or manned aircraft, drones can generate high-resolution, highly accurate data in real-time and with less cost. Drones can also fly almost anywhere, and thereby gather data in inaccessible or unsafe places. 

How Does a Drone Survey Work?

Drones fly above the ground to capture aerial images of a project area using RGB and multispectral cameras. Drone solutions also feature LiDAR payloads to help in gathering data, especially in measuring the exact distance of an object on a given area.  A drone used in land surveys will survey the project area and use its cameras to take photos of the land from different angles. Images captured – each of them – have the exact coordinates of the site. 

How Do Drones Collect Data?

A computer system called Geographic Information System (GIS) is the primary source for drones for collecting data. They utilized this information to map out and visualize locations. However, drones can be equipped with other data collection tools in performing land surveys.  Before, drones only captured data but couldn’t transmit them. The operator had to retrieve all the information. With GIS technology, drones can now transmit information in real-time, and even turn raw data into actionable information. 

How Accurate are Drone Surveys?

For newbies in using drones, it’s natural to be concerned about its accuracy. But to calm you down, drones are highly accurate. In many cases, drone survey results are expected to be accurate to around 2-3 centimeters horizontally and around 5-6 centimeters vertically. Using a high-end drone in optimal conditions, you can reach a level of accuracy to around 1 centimeter (0.4 inches) and 0.7 centimeters/pixels (0.3 inches/pixels) GSD.  The outcome of a drone survey will be influenced by the type of drone you’re using, the camera quality, the height of the drone flight, the ground cover, and the technology and method used in geolocating the aerial images. It’s not difficult to avail of high-quality commercial drones to get highly accurate survey results nowadays. 

Why Are Drone Surveys Better Compared To Traditional Methods?

Drones do an excellent job at rapidly capturing topographic data of a given area. It’s five times faster compared to land-based methods, and you don’t need more manpower to generate desired survey outcomes. You can also save a great amount of time if you use PPK geotagging, as you won’t need to place numerous GCPs. Using drones, you can collect data from vantage points that are otherwise challenging and unreachable to humans. You’ll no longer be limited by harsh terrains, steep slopes, or inaccessible areas. There’s no need to close down a street or highway just to perform a survey of a project area if you have a drone that can capture data from above.  Compared to traditional surveying methods, drone surveying provides accurate and exhaustive data. Total stations, for instance, generate individual point measurements, while drones produce a greater number of measurements that can be represented in several formats (DTM, DSM, point cloud, contour lines, orthomosaic, etc.) Each map generated by a drone also contains 3D geo-data.  Despite the upsides of using drones in surveying, there are disadvantages that you need to know. One of them is the confusing and changing drone regulations, especially in cities or urban areas. There’s also the need to hire an experienced and well-trained professional to operate the drones as the results can turn inaccurate if drones are operated by just anyone. Moreover, drones may not be ideal to use in places that regularly experience high winds. 

What Kinds of Drones are Used for Surveying?

You can find a lot of commercial drones nowadays. If you want to use one for surveying, buy a drone with features that can handle the job to be done. There are drones with multirotor on the market, but one with a fixed-wing motor is much better for mapping surveys.  Yes, you can fly a multirotor drone with less hassle, but a fixed-wing drone is ideal to handle surveys on large plots of land. Fixed-wing models can stay longer in the air compared to multirotor models. That’s why they’re preferable over multirotor drones, especially for large-scale surveys.  It’s also smart to pick a drone that has an autonomous flight feature because you need to fly this tool over an area multiple times for aerial mapping. If it has no autonomous flight feature, you can create a flight path for your drone using a software. After creating the flight path, send the information into the remote control for a pre-programmed flight.  Since you need to survey acres of land in an aerial mapping, many drones don’t have the battery capacity to fly without interruption in a single mapping. Precious time will be wasted if you fly the drone and land to recharge or change batteries. That’s why buy a drone that can hover above the ground for at least 30 minutes to an hour with no interruption.  Moreover, choose a drone with a camera that can take 12 MP images and 4k videos for 3D mapping work. This kind of camera is also a requirement for photogrammetry, which is a technique that utilizes geotagged images to infer the dimension on the surface and catalog data. 

What Kinds of Deliverables Can You Achieve With Drone Surveying?

Depending on the software, camera, and sensor you’re using, several deliverables can be achieved by a drone as an instrument for surveying. 

LiDAR Point Cloud

Many surveying drones are equipped with LiDAR to see through vegetation, trees, and any ground cover. This sensing method or software is crucial in data collection on a project area with too many obstacles.  The collected data will generate a densified point cloud containing color and geospatial information (X, Y, Z). This gives a highly accurate model for area, volume, and distance (horizontal and slant) measurements. 

Thermal Maps

Drones can generate images and help identify areas with abnormal heat signatures. The drone can survey cities, campuses, facilities, military bases, and complexes for thermal images. You can monitor supply steam pipes, supply water mains, condensation return lines, and hot water lines through a drone inspection. 

Multispectral Map

Drones can also collect a type of data called a multispectral map. This technique captures images within a particular wavelength range on the electromagnetic spectrum. Multispectral maps help give insights into agriculture and crop management. 

3D Models

Producing 3D models from data collected is also one of the reasons drones are used in surveying. Drones scan a survey site to capture data sets related to large objects like buildings and construction sites. After collecting data, you can make a 3D model using 3D software for a more comprehensive site analysis. 

3D Orthomosaics

3D orthomosaic maps can solve issues with 2D projection. No wonder drones that can capture several hundred images and catalog them into a 3D map are popular today. With these 3D orthomosaics, land surveyors can get their hands on better topographic data.  Drones can be integrated with Building Information Modeling (BIM) in a construction survey. A high-res 3D map can be generated and compared with BIM objects in every construction step to identify discrepancies and resolve them. 

2D Orthomosaic Maps

Orthomosaic maps are created by drones with 2d photogrammetry mapping capabilities. A drone can snap hundreds of images from above and compile them to create 2D orthomosaic maps.  Such maps feature unformed scales, and you can use them to calculate distances between specific points. They’re an accurate representation of the geological surface of the earth, according to many land surveyors. 

Will Drones Replace Land Surveyors?

While traditional surveys are increasingly superseded by drone surveys, it’s impossible, however, to replace land surveyors with drones. Drones only serve as tools to be used by surveyors. They’re a big help in the latter’s work in terms of safety, efficiency, and accuracy, but drones can’t take away the genius and experience of a land surveyor to find solutions to meet a client’s needs. 

Takeaway

I hope you’ve learned a thing or two about land surveying using drones in this blog post. Drone surveying is a popular method of land surveying today. Drones help land surveyors to map out survey sites and generate deliverables with efficiency and accuracy. Using drones also significantly reduces the cost of performing surveys.