Table of Contents

• What are drone point clouds?

• Photogrammetry with drones

• Challenges in drone point cloud processing

• Realizing rapid 3D surveying

• Centimeter-level high-precision positioning (cm level accuracy (half-inch accuracy))

• Cost reduction and labor savings benefits

• Use cases for LRTK drone point clouds

• Simple 3D surveying with LRTK

• FAQ

What are drone point clouds?

Recently, in the construction and civil engineering industries, the term “point cloud data” has become increasingly common. A point cloud is, simply put, a large collection of points in three-dimensional space that digitally records the shape of objects or terrain as they are. Each point contains X, Y, and Z coordinates (positional information) and may also include color or reflectance intensity information as needed. For example, when terrain or structures are measured with a laser scanner or camera, the surface geometry is recorded as a multitude of points. When displayed on a computer, the collection of points reproduces the object three-dimensionally, and can be handled as a highly detailed 3D model that can look almost photographic.

So what is a “drone point cloud”? It is point cloud data acquired using a drone (unmanned aerial vehicle). Traditionally, ground surveying required surveyors to observe each point one by one to create topographic maps, but with a drone you can capture the entire ground surface from above at once, enabling detailed areal surveying. By generating three-dimensional point clouds from data obtained by cameras or sensors mounted on drones, extensive terrain and structures can be digitized in a short time. In recent years, drone-based 3D measurement has begun to spread, and its applications are expanding beyond civil engineering and surveying to include disaster prevention, infrastructure inspection, and urban planning. The fusion of techniques developed in aerial photogrammetry with the latest digital technologies is making drone point clouds an increasingly accessible surveying method. Additionally, since drones can remotely record conditions in hazardous areas where people cannot safely enter, they also contribute to improved safety.

Photogrammetry with drones

A common method for obtaining point cloud data with drones is photogrammetry. Photogrammetry is a technique that reconstructs the 3D shape of a subject from multiple aerial photographs taken by a camera mounted on a drone, using overlapping images. The drone flies automatically and captures high-frequency images from the air; those images are later processed by analysis software to generate point clouds and orthophotos (composite overhead images). In this processing, common feature points that appear in multiple photos are matched to estimate the camera positions and orientations, and three-dimensional coordinates are calculated (this method is also known as Structure from Motion, or SfM). As a result, detailed point cloud models of terrain and buildings are obtained, and each point is often assigned color information derived from the photographs.

Generating point clouds via photogrammetry has a major advantage in that it can be undertaken at a lower cost compared with methods using dedicated laser scanners. Even without expensive LiDAR equipment, sufficiently high-density point clouds can be created with commonly available aerial photography drones and cameras. Also, 3D models generated from photos include texture (photographic surface detail), producing visually clear point clouds and 3D maps. Drone photogrammetry is recognized as a labor-saving technology in the i-Construction initiative promoted by the Ministry of Land, Infrastructure, Transport and Tourism, and it is already being used in surveying and construction management operations.

Of course, besides photogrammetry, drone-based point cloud acquisition can also be done using drones equipped with laser scanners. Laser-equipped drones can perform laser measurements directly from the air and acquire high-precision point clouds in real time. However, laser scanner–equipped models have very high equipment costs and require specialist expertise, so they are currently mainly limited to large-scale projects or special applications. On the other hand, photogrammetry is relatively easy to introduce, so the combination of drone + photogrammetry has become mainstream in general civil surveying.

Furthermore, introducing photogrammetry can greatly reduce surveying time. For example, there are reports that a survey that used to take three days with a total station for several hectares was completed in about half a day using drone photogrammetry.

Challenges in drone point cloud processing

Creating point cloud data from photos taken by drones is groundbreaking, but there have still been several challenges in that data processing.

• High-performance PCs and dedicated software are required: Generating point clouds from drone photos, especially with large numbers of images, previously required high-performance computers with GPUs. Also, the specialized software for SfM (photo analysis software) is costly, leading to licensing fees and the burden of learning to operate it.

• Long processing times: Analyzing hundreds of photos to obtain point clouds and orthophotos traditionally took several hours or, in some cases, more than a day. Even if images are captured on site, results could not be confirmed immediately; users had to wait for data processing to finish, making rapid decision-making or same-day deliverables difficult.

• Effort required for high precision: To give absolute positioning accuracy to point clouds obtained by photogrammetry, it was necessary to place ground control points (GCPs) to provide precise coordinates. Alternatively, using expensive RTK-capable drone platforms is an option, but this can be a high hurdle for small and medium-sized businesses. These efforts to ensure accuracy undermined the ease of drone surveying.

• Difficulty in data management and sharing: Point cloud data and the generated 3D model files become very large. Traditionally, sharing processed point clouds within a company or importing them into CAD software for use was difficult. Files could be too large to send by email, and without dedicated viewer software stakeholders could not view the data. As a result, there were many cases where obtained point cloud data could not be fully utilized.

Realizing rapid 3D surveying

To solve the above challenges, a drone point cloud service using cloud automated processing has emerged. LRTK drone point clouds leverage this cloud technology to speed up data processing and streamline fieldwork.

Whereas photo analysis used to be done on a PC back at the office for long hours, with LRTK you can upload images to the cloud via the internet directly from the field and have them processed automatically. Large volumes of image data are processed in parallel on powerful cloud servers, greatly reducing waiting times. For example, if point cloud generation is started via the cloud on the same day images are captured, results can sometimes be obtained within a few hours, allowing onsite conditions to be assessed. This enables same-day rapid deliverable provision and quick decisions on additional photography or re-surveying as needed.

Cloud automated processing also minimizes manual operations, reducing the workload on personnel. Without worrying about complex software settings or error handling, advanced analysis is completed simply by uploading captured data. Field personnel can proceed with other tasks while processing runs, improving overall operational efficiency. Using LRTK drone point clouds makes 3D surveying, which used to take a long time, significantly faster, contributing to rapid decision-making and shortening project schedules. In addition, cloud platforms can process multiple projects concurrently, minimizing waiting times.

Centimeter-level high-precision positioning (cm level accuracy (half-inch accuracy))

Ensuring positioning accuracy in drone surveying is critically important. As the name LRTK suggests, this service incorporates high-precision positioning based on RTK (Real-Time Kinematic) technology. RTK is a technique that applies correction information to satellite positioning like GPS to reduce measurement errors to the centimeter level (cm level accuracy (half-inch accuracy)). LRTK uses RTK correction information via the cloud to assign high-precision positional information to photos captured by drones.

Specifically, by using LRTK drone point clouds, the work of placing GCPs that was previously necessary can be greatly reduced. By precisely determining the drone-mounted camera positions and the coordinates of the photographing points using RTK methods, the output point cloud model is accurately registered in the geographic coordinate system. The accuracy improves from errors on the order of several meters (several ft) with standalone GPS to the order of a few centimeters (a few in) when using RTK. This means the acquired point cloud data can be overlaid on existing drawings or GIS data with almost no offset. Reliable values can be obtained for surveying drawings and earthwork volume calculations, so it can be used with confidence for design, construction planning, and quality control. LRTK drone point clouds make it possible to achieve public-survey-level high precision with a much simpler workflow than before.

Cost reduction and labor savings benefits

One major advantage of introducing LRTK drone point clouds is cost reduction and labor savings. Traditionally, obtaining 3D survey data required expensive equipment investments and securing specialized personnel. For example, purchasing laser scanners or RTK-capable drones, or paying for photo-processing software licenses, imposed burdens on companies. Data processing and drawing creation required skilled personnel for long hours, increasing labor costs.

However, by using LRTK’s cloud service, these initial investments and operational costs can be substantially reduced. With a commercially available aerial photography drone and a smartphone, you can start the service without purchasing special surveying equipment. Since analysis software is provided in the cloud, there is no need to acquire expensive software in-house. Data processing is automated, so there is no requirement to maintain specialized operators full-time; personnel can obtain survey results while handling multiple duties with a small team. Also, by using a cloud service you can always use the latest analysis technology without the burden of updating software or maintaining hardware in-house.

Furthermore, the ease of use means you can conduct surveying whenever necessary and only as much as needed. Surveys that were previously limited to specific times due to cost can now be done frequently at low cost with LRTK. For example, it becomes realistic to record construction progress weekly with drone point clouds. Labor savings free field technicians to spend time on other tasks, contributing to work-style reform. In this way, LRTK drone point clouds enable inexpensive, low-effort 3D surveying and offer a solution that is easy to introduce for projects of any scale.

Use cases for LRTK drone point clouds

LRTK drone point clouds can be used in a wide range of scenarios. Here are some representative examples.

• Civil engineering surveying: Surveying the current terrain of development or planned construction sites quickly by drone and creating 3D topographic maps for design. Also useful for post-construction as-built surveys.

• Construction progress management: Periodically aerially photograph construction sites with a drone and compare the obtained point cloud data with previous datasets to visualize increases or decreases in earthwork and the degree of progress. This objective record is also useful for preparing reports.

• Earthwork and volume calculations: Automatically calculate excavation and fill volumes from point clouds to streamline quantity management. Tasks that used to be done manually can now yield accurate figures simply by specifying areas on the point cloud data.

• Infrastructure inspection: Photograph bridges, dams, slopes, and other infrastructure with a drone to generate high-resolution point cloud models. Cracks or displacements can be measured on a desktop, and year-to-year comparisons can reveal long-term changes.

• Disaster response and disaster prevention planning: Rapidly photograph landslide or flood sites by drone and generate point cloud models of affected areas. The volume of collapsed soil or the extent of inundation can be determined promptly, providing materials for initial response and recovery planning. In normal times, it is also useful for regular monitoring of hazardous locations.

As described above, LRTK drone point clouds are powerful across many applications, from construction and civil engineering sites to infrastructure maintenance and disaster prevention. Even where time or cost constraints previously prevented usage, it will now be easy to obtain 3D data and apply it to operations.

Simple 3D surveying with LRTK

With the utilization of drones and cloud processing, 3D surveying has become more familiar and simpler than ever. Using LRTK drone point clouds, anyone can obtain precise three-dimensional data without special equipment. Even those trying drone surveying for the first time can proceed smoothly with the intuitive smartphone app and automated processing.

The wave of 3D point cloud utilization is spreading steadily and will become an indispensable technology in future field digital transformation. For companies or departments that have not yet introduced it, it is not too late with LRTK. Because trials can be started at low cost and low risk, begin with small projects to experience the effects. You will likely be surprised at how different it is from traditional methods.

Leverage the latest technology to bring efficiency and higher precision to your field. Open up new possibilities in your work with LRTK’s simple 3D surveying.

Take your site to the next stage with LRTK.

FAQ

Q. What equipment is needed to use LRTK drone point clouds? A. Basically, you can start with a commercially available drone and a smartphone. Upload the images captured by the drone to the LRTK cloud via your smartphone to generate point clouds. Even when high-precision positioning is required, you do not need to purchase expensive dedicated equipment (LRTK’s GNSS receiver device can be used as needed, and integration with existing RTK drones is also possible).

Q. Can it be used without prior drone surveying experience? A. Yes, LRTK is designed to be easy to use even for beginners. Simply fly the drone following instructions in the dedicated app and send the captured data to the cloud, and point clouds will be generated automatically. Complex analysis is handled on the cloud side, so operators do not need specialized knowledge. With about five minutes of on-site operation guidance, anyone can start 3D surveying that same day.

Q. How accurate are the output point clouds? A. It depends on conditions, but by using RTK positioning you can generally expect accuracy within a few centimeters (a few in). Because LRTK’s RTK corrections improve the positional accuracy of each photo even without placing ground control points (GCPs), the resulting point cloud model also has high absolute accuracy. However, accuracy varies with flight altitude and satellite reception conditions, so for critical measurements it is important to fly under sufficient satellite coverage.

Q. How large an area can be surveyed? A. This depends on the drone’s performance and battery endurance, but even small drones can capture on the order of several tens of hectares in a single flight. For large sites, divide the area and fly multiple missions, then merge the data into a single point cloud model. The LRTK cloud supports large volumes of image data, so it can be used with confidence for wide-area surveying projects.

Q. How can the created point cloud data be used? A. You can view point clouds in a 3D viewer on the LRTK cloud, measure distances, areas, and volumes, and create cross-sections. Point cloud data (in LAS or PLY formats, for example) and orthophotos can be downloaded as needed and imported into CAD or GIS software for design and analysis. You can also issue shared links on the cloud to allow stakeholders to view the point cloud model via a browser for collaborative review. Because the acquired data can be reused for many purposes, a single survey can generate significant added value.

Q. How long does cloud processing take? A. It varies by data volume, but for a few hundred photos processing is often completed within a few hours. Analyses that used to take a full day on a PC can finish quickly in the cloud, so results may be viewable on the same day as capture. For very large projects, processing may take half a day to a day, but operators do not need to wait on site; they will be notified and can check results as soon as they are available.