Drone + Point Clouds Make Volume Calculation Easy! Site Supervisors Will Be Amazed by the Efficiency Gains

Table of contents

• What is point cloud data?

• How to acquire point clouds with a drone

• How to calculate volume from point cloud data

• Benefits of volume calculation with drones + point clouds

• Cases of efficiency gains that surprised site supervisors

• Key points and cautions when using drones

• What is simple surveying with LRTK?

• FAQ

Volume calculation of earthworks such as fills and excavations is an essential task for schedule management and progress verification at construction and civil engineering sites. Traditionally, calculating earth volumes required surveying the terrain with surveying instruments, creating cross sections, and then spending significant time and effort performing manual calculations using the average cross-section method. Nowadays, however, by utilizing drones and high-density point cloud data, anyone can efficiently compute accurate volumes. Deriving volumes from 3D point cloud models created by photographing the entire site from above is far easier and faster than traditional methods would allow. In practice, even site supervisors without surveying expertise can quickly grasp the required earth quantities using digital technology, and they are often astonished by the speed and efficiency.

This article explains what point cloud data—the basis of drone-based volume calculations—is, how to acquire it, and how volume is computed from it. We also describe the benefits of using drones + point clouds, real-world cases of efficiency gains, and operational cautions. At the end of the article, we touch on a new simple 3D surveying method, LRTK-based simple surveying, which does not use drones, and introduce the latest trends in site DX.

What is point cloud data?

First, let’s cover the key concept of point cloud data. Point cloud data is a collection of many measured points in space, with each point carrying X, Y, and Z coordinate (position) information—i.e., three-dimensional data. In other words, it is like a digital “3D model” that captures the shape of a site with countless points. Points may also include attributes such as color information or laser return intensity.

In traditional manual surveying, measured points were limited to a certain number (on the order of tens to hundreds). In contrast, point clouds obtained by drones or laser scanners can contain millions of points from a single measurement. Because the site can be measured densely, small undulations in terrain and fine details of piled materials can be accurately reproduced. Such detailed measurement via 3D surveying is also encouraged for use in initiatives like *i-Construction* promoted by the Ministry of Land, Infrastructure, Transport and Tourism, and it is rapidly spreading across the construction industry.

How to acquire point clouds with a drone

So how do you acquire point cloud data using a drone? Broadly, there are two methods for 3D measurement with drones: photogrammetry (Structure from Motion) and laser scanning (LiDAR).

• Point cloud generation by photogrammetry (SfM): This method uses a camera mounted on a drone to take many photographs of the ground and objects from various angles, and software analyzes the images to generate point clouds and 3D models. This is also known as Structure from Motion (SfM). Drones can capture wide areas quickly, and recent advances in image processing have made it relatively easy to create high-accuracy point clouds. However, to obtain precise dimensions and coordinates, it is effective to set and measure ground control points (GCPs) in advance to tie measurements to surveying coordinates, or to use an RTK-capable drone for imaging.

• Point cloud acquisition by laser scanning (LiDAR): This method mounts a lightweight LiDAR sensor on a drone and directly acquires three-dimensional point clouds by measuring laser emission and return. Laser scanner surveys can capture extremely dense data on the order of millions of points in a single flight and can achieve accuracy down to the millimeter level (0.04 in). Unlike photogrammetry, LiDAR can penetrate gaps in tree foliage to capture the ground beneath and can operate in dim conditions. Drone-mounted LiDAR has recently become smaller and higher performance, and the accuracy of acquired data is generally reported to be on the order of a few centimeters (a few in).

In both methods, point clouds obtained from drones are tied to position coordinates (such as latitude/longitude or plane rectangular coordinate systems). By combining drones equipped with RTK-GNSS or by integrating ground control surveys, the acquired point cloud model can be aligned to real-world surveying coordinate systems (georeferenced). As a result, analyses such as measuring distances and areas directly on the point cloud or comparing it with design data become possible.

How to calculate volume from point cloud data

How do you perform volume calculations from acquired point cloud data? The key is to reconstruct the terrain surface from the point cloud data and compute volume based on that surface. Fortunately, dedicated point cloud software and cloud services have become well developed in recent years, making volume calculation possible without dealing with complex computations.

There are two representative scenarios for volume calculation. One is determining cut-and-fill quantities by differencing terrain before and after construction; the other is calculating the volume of a single mound such as a stockpile.

• Earthwork calculation by differencing pre- and post-construction point clouds: To accurately determine fill and excavation volumes caused by works such as site development, it is effective to survey the site as point clouds both before and after construction and calculate the difference. Specifically, you overlay the pre-construction baseline point cloud and the post-construction point cloud and compute the height differences. Software capable of volume comparison between point clouds will automatically calculate the volumes of removed or added areas, enabling accurate determination of cut-and-fill quantities. Because the difference is computed over the entire surface rather than section-by-section, subtle undulations and local variations are captured, allowing highly accurate quantity control.

• Volume calculation of a single mound relative to a reference plane: When you want the volume of a single lump such as a pile of excavated soil or a stockpile, you treat the surrounding ground as a reference plane. On the point cloud, you draw a polygon around the target mound, set the reference surface elevation, and the volume of the portion protruding above the reference plane within that polygon is automatically calculated. In other words, it is like integrating the solid volume obtained when you cut the raised soil with an imaginary flat plane from below. Most point cloud processing software lets you specify the area and the reference height (for example, the average elevation of surrounding ground), and with a click the volume for that region is displayed.

Thus, volume calculation based on point cloud data is almost fully automated in software. Previously, you had to create a mesh model from the point cloud and then compute volume, but nowadays some services will compute volumes simply by uploading point cloud data to the cloud. Even without advanced 3D CAD skills, user-friendly point cloud viewers and analysis tools let you intuitively derive earth quantities.

Benefits of volume calculation with drones + point clouds

Compared with traditional manual earth volume calculations, using drones and point clouds offers many advantages. Here are the main benefits.

• Significant time savings and labor reduction: Flying a drone completes data acquisition over large sites in a short time. Manual surveying could take several days to measure expansive sites, but drone aerial imaging can cover an entire site in just tens of minutes to a few hours. Subsequent volume calculation is automated by software, dramatically reducing the time spent on manual calculations and drawing. As a result, the total work time for volume measurement is greatly shortened, enabling efficient operations with limited personnel.

• Reduction of human error and improved accuracy: Calculations based on point clouds are highly reproducible and yield the same results regardless of operator. Reliance on an experienced surveyor’s intuition or manual calculation errors is minimized, reducing human-induced errors. Also, because point clouds record the site densely, there are no partial oversights, and overall high accuracy in quantity estimation is expected. In fact, there are reports that earth volumes calculated from drone photogrammetry or terrestrial laser scans differed from traditional cross-section methods by only about 1–2%. With proper measurement methods, volume calculations using point clouds can match the accuracy of traditional methods.

• Improved safety: A major advantage is the ability to survey hazardous areas without physical contact. There is no need for personnel to enter steep or unstable slopes; drones can safely collect data from above. Assigning high or difficult-to-access measurements to an aerial robot reduces fall risks for workers and contributes to safety management.

• Immediate feedback and sharing: Point cloud data is digital, so it can be analyzed and shared on a PC or in the cloud immediately after acquisition. Volume results can be shared with stakeholders on the same day as the survey, and comparisons with design drawings can be made quickly, enabling swift decision-making. This allows timely adjustments to construction plans or additional countermeasures as needed.

Owing to these benefits, earth quantity calculations using drones + point clouds are a powerful solution for construction sites where productivity improvements are urgent. As a countermeasure to the 2024 labor regulation changes for the construction industry (the so-called “2024 problem”), digital technology–driven operational efficiency is indispensable. Introducing drone surveying can help address chronic labor shortages and support workstyle reform.

Cases of efficiency gains that surprised site supervisors

How much efficiency improvement is realized in actual sites that have introduced drone and point cloud–based volume measurement? In one large-scale reclamation site, measuring earth quantities that previously took three people two days to complete was finished in less than half a day after introducing drone surveying. The drone’s aerial imaging time was about 15 minutes, and after uploading the photos to a cloud point cloud generation service, a high-accuracy point cloud model and orthomosaic were produced within a few hours. Using that point cloud data, fill and excavation volumes were calculated, and the site supervisor was reported on the same day—so quick that the person in charge could hardly hide their surprise.

In another case, automating the monthly measurement of accumulated soil with drones cut work time to less than one-quarter of the prior time. Because aerial imaging can capture areas that people cannot access, there were no measurement omissions that would cause rework. Digital surveying with drones is changing on-site norms with its speed and efficiency, and at first-time adopter sites, it is often met with the supervisor asking, “Is it really already finished?”

The Ministry of Land, Infrastructure, Transport and Tourism also reports that sites adopting ICT construction (3D surveying and machine guidance, etc.) achieved average work time reductions of more than 30%. It’s not just finishing faster: improved reliability of measurement results reduces rework, and more frequent quality control enables earlier detection and correction of defects, producing significant secondary benefits. Drone-based point cloud surveying is therefore an innovative means to simultaneously improve the quality and efficiency of site management.

Key points and cautions when using drones

There are several points to keep in mind when performing drone point cloud surveys. To avoid trouble even after introduction, pay attention to the following.

• Regulations and flight permissions: Drone flights must comply with rules such as the Civil Aeronautics Act. Prior permission and approval from the Minister of Land, Infrastructure, Transport and Tourism are required for flights over densely populated areas, night flights, beyond-visual-line-of-sight flights, and so on. Since 2022, a licensing system regarding drone airframes and operators has also begun, so when flying for business purposes, confirm the latest regulations and obtain necessary qualifications or notifications. For safety, ensure surrounding parties are informed and monitoring systems are in place before flight.

• Consideration of weather and environment: Drones cannot be flown in rain or strong winds. Forcing flights not only increases crash risk but also degrades data quality. Monitor weather forecasts and plan flights on days with stable conditions. Also be mindful of environmental factors such as blown-out highlights from strong sunlight or lens contamination from dust. Choose times such as early morning or late afternoon when lighting is stable if necessary.

• Data volume and processing time: High-density point clouds produce large files and can take time to process. If analyzing on a PC, a high-performance machine is desirable, but many cloud services now handle heavy processing online. Photogrammetry processing from a large number of photos can often be completed by uploading to the cloud without owning the software in-house. Consider a mix of on-premises and cloud processing according to site conditions.

• Accuracy verification and correction: To trust point cloud survey results, verifying the accuracy of acquired data is essential. Check GNSS errors of drone-mounted receivers against known points before and after flights, and compare elevations of generated point clouds with ground checkpoints to ensure the expected accuracy. Performing georeferencing with control points and accurately registering multiple flight point clouds improves final earth volume calculation accuracy. Noise removal and interpolation for missing areas also affect result quality. Don’t rely solely on automatic software functions—perform expert oversight at key steps.

If you operate while keeping these points in mind, drone surveying becomes a powerful tool. That said, there are sites where “you can’t fly a drone even if you want to.” For example, drone flight may be difficult for legal reasons in urban areas, or physically impossible in tunnels or indoors, or impractical when you need immediate small-scale measurements. In such cases, having an alternative way to easily perform 3D surveying without a drone is useful. The next section introduces LRTK-based simple surveying, a new method that answers these needs.

What is simple surveying with LRTK?

LRTK is a solution that consists of a small high-precision GNSS receiver that attaches to a smartphone and a dedicated app. Using RTK-GNSS satellite positioning technology, it corrects position errors in real time to achieve centimeter-level positioning with a smartphone. Simply put, attaching an LRTK device to your everyday smartphone instantly transforms it into a high-precision surveying instrument.

By combining it with a smartphone’s built-in LiDAR scanner or camera, anyone can easily acquire 3D point clouds with high positional accuracy. The pocket-sized device weighs a few hundred grams and can be carried to the site at all times, offering the convenience of measuring whenever needed.

When measurements are taken with the LRTK app, acquired point cloud data and coordinate information for measured points are immediately synchronized to a cloud system. The data is displayed in 3D on a browser-based point cloud viewer, and distance, area, and even volume calculations can be performed on the spot. For example, if you scan a mound of surplus soil with your smartphone and upload it to the cloud, a point cloud model is generated in tens of seconds to a few minutes and the volume is automatically calculated and displayed. There is no need to return to the office for PC-based analysis; you can grasp the required quantities from the site immediately.

The main advantages of LRTK simple surveying are that it is intuitive to operate single-handedly and that anyone can do it. Even without mastering drone piloting or traditional surveying equipment, following the smartphone app’s instructions completes 3D surveying. Another major benefit is lower equipment cost. You often don’t need to purchase an expensive laser scanner or outsource to an external surveying firm; a smartphone and a relatively inexpensive GNSS device may suffice. In short, LRTK provides an environment where “anyone can measure immediately when they want to.” Because of this ease and affordability, LRTK is a cutting-edge site DX tool that aligns well with the i-Construction movement advocated by the Ministry.

Surveying technology is thus becoming both more advanced and more accessible. While drone-based point cloud surveying is an excellent solution, having ground-based quick methods like LRTK makes 3D data use on site even more flexible and widespread. If you are considering using 3D surveying on your site, starting with smartphone + LRTK simple surveying is a good option. Detailed information and consultations on introduction are available on LRTK’s official website, so check it out if interested. Incorporate the latest technologies wisely to help boost productivity on your site.

FAQ

Q: Do I need qualifications or flight permission to perform volume calculations with a drone? A: When using drones for business, certain flights require applications or qualifications with the Ministry of Land, Infrastructure, Transport and Tourism depending on the flight content. Unmanned aircraft flights are regulated by aviation law; for example, flights over densely populated areas (DID areas), beyond-visual-line-of-sight or night flights, and flights of aircraft weighing 25 kg or more require prior permission/approval. From the end of 2022, a licensing system for drone pilots was also introduced, and for certain flight conditions (such as Level 4 flights) a national qualification is required. However, daytime visual-line-of-sight flights at unpopulated sites generally do not require a license, and flights are possible if training completion and other conditions are met. In any case, acquiring knowledge for safe flight is essential, so consider training at a drone school or obtaining skill certification for peace of mind.

Q: How reliable is the accuracy of volumes calculated from point cloud data? A: With appropriately acquired point cloud data using correct surveying methods, volume calculation accuracy can be considered comparable to traditional surveying methods. In practice, earth volume calculations using drone photogrammetry or terrestrial LiDAR often differ from traditional average cross-section methods by only a few percent. In short, you can often obtain nearly the same numbers as careful conventional measurements. However, ensuring high accuracy requires proper setup of initial control points, instrument calibration, and accurate registration of point clouds during processing. Noise and missing data in point clouds can also introduce errors, so optimizing shooting conditions and filtering out unnecessary points are important. When conditions are met, point cloud–based volume calculation is highly reliable.

Q: Are drone and software operation or data processing difficult? A: Recent software and cloud services for drone surveying are designed to be user-friendly, and basic operations are not especially difficult. Drone airframes also have well-developed autonomous flight and safety features, enabling stable flights when procedures are followed. Photogrammetry processing from captured photos is often guided by dedicated software or can be completed simply by uploading data to the cloud. Point cloud viewer measurement operations are generally intuitive—select functions such as “distance measurement” or “volume calculation” from menus and click. You may feel unsure at first, but many tools provide tutorials and support information, and you will become accustomed quickly. Advanced use requires training, but obtaining volumes does not require special programming or expert knowledge.

Q: How should I measure volumes where drones cannot be flown? A: If drone flights are restricted by regulations or site conditions, several alternatives exist. One is ground-based photogrammetry: if aerial imaging is not possible, take many photos around the target while walking around it; later, software can analyze these to create a 3D model. For small mounds, ground-based photogrammetry is often sufficient. Also, methods to measure point clouds using smartphones or tablets have become practical. As mentioned earlier, combining a smartphone with high-precision GNSS like LRTK enables centimeter-level point clouds without a drone, which can be used directly for volume calculation. In addition, fixed terrestrial laser scanners mounted on tripods (terrestrial LiDAR) have long been used for ground measurements. Choose among these methods based on site conditions and constraints. The important thing is to obtain 3D surveying data by any suitable means; once you have that data, software can consistently perform the volume calculations. Acquire point clouds by the best method for your site and advance digital quantity management.