LRTK Drone Point Clouds: Achieving Fast, High-Precision, Low-Cost 3D Surveying with Cloud Automated Processing

Table of Contents

• What is a drone point cloud?

• Photogrammetry using drones

• Challenges in drone point cloud processing

• Achieving rapid 3D surveying

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

• Benefits of low cost and labor savings

• Use cases for LRTK drone point clouds

• Easy 3D surveying with LRTK

• FAQ

What is a drone point cloud?

Recently, the term “point cloud data” has been heard more often in the construction and civil engineering industries. A point cloud, simply put, is a collection of many points in three-dimensional space, digital data that records the shape of objects and terrain as they are. Each point contains X, Y, and Z coordinates (positional information), and may also include color or return intensity information as needed. For example, when terrain or structures are measured with a laser scanner or camera, the surface shape is recorded as an assembly of countless points. When displayed on a computer, the cluster of points reproduces the object’s shape three-dimensionally, and can be handled as a detailed 3D model so realistic that it can look like a photograph.

So what is a “drone point cloud”? It is point cloud data obtained using a drone (unmanned aerial vehicle). Traditionally, ground surveys involved surveyors observing each point one by one to create topographic maps, but using drones makes it possible to photograph the entire ground surface from above at once, enabling detailed areal surveying. By generating three-dimensional point clouds from data obtained by cameras and sensors mounted on drones, wide areas of terrain and structures can be digitized in a short time. In recent years, such 3D measurement by drones has begun to spread, and its use is expanding not only in civil engineering and surveying sites but also in disaster prevention, infrastructure inspection, urban planning, and various other fields. The fusion of technologies cultivated in aerial photogrammetry with the latest digital technologies has made drone point clouds an increasingly familiar surveying method. Also, because drones can safely record conditions remotely in hazardous locations where people cannot enter, they contribute to improved safety.

Photogrammetry using drones

A common method for obtaining point cloud data with drones is photogrammetry. Photogrammetry is a technique that reconstructs the 3D shape of an object from multiple aerial photographs taken by a camera mounted on a drone, using overlapping photos. The drone acquires high-frequency images from the air via automated flight, and those image sets are processed later with analysis software to generate point clouds and orthophotos (composite images viewed from directly above). This processing matches common feature points that appear in multiple photos, estimates the camera positions and orientations, and calculates three-dimensional coordinates (a method also called Structure from Motion or SfM). As a result, detailed point cloud models of terrain and buildings are obtained, and each point is also assigned color information derived from the photos.

Generating point clouds via photogrammetry has a major advantage in that it can be done at a lower cost compared with methods using dedicated laser scanners. Even without expensive LiDAR equipment, sufficiently dense point clouds can be created using a commercially available aerial drone and camera. In addition, 3D models generated from photos also have textures (photographic surface information), resulting in visually clear and easily understandable point clouds and 3D maps. In the i-Construction initiative promoted by the Ministry of Land, Infrastructure, Transport and Tourism, drone photogrammetry is recognized as a labor-saving technology on-site, and its use in surveying and construction management tasks is already advancing.

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

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

Challenges in drone point cloud processing

Creating point cloud data from photos acquired by drones is revolutionary, but there were still several challenges in that data processing.

• High-performance PCs and dedicated software are required: To generate point clouds from drone photos, a high-performance computer with a GPU was required when the number of photos was large. Also, the specialized software for performing SfM (photo analysis software) was expensive, 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 to sometimes more than a day of computation. Even if images were captured on-site, results could not be confirmed there, and one had to wait for data processing to complete, making quick decision-making and same-day deliverables difficult.

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

• Difficulty in data management and sharing: Point cloud data and the generated 3D model files become very large. Traditionally, it was difficult to share processed point clouds within a company or import them into CAD software for use. The data size was too large to send by e-mail, and without dedicated viewer software, it was hard to share with stakeholders. As a result, there were cases where acquired point cloud data could not be fully utilized.

Achieving rapid 3D surveying

To solve the challenges above, drone point cloud services using cloud automated processing have emerged. LRTK drone point clouds leverage this cloud technology to speed up data processing and improve on-site work efficiency.

Whereas photo analysis used to be done on a PC for long hours after returning to the office, with LRTK you can instantly upload data from the field to the cloud via the Internet and trigger automated processing. Large volumes of image data are processed in parallel on powerful cloud servers, greatly reducing waiting times. For example, if you start point cloud generation via the cloud on the day of shooting, you may be able to obtain results within a few hours in the best cases and grasp the site situation. This enables same-day rapid deliverables and swift decisions on additional shooting or re-surveying if needed.

Also, cloud automated processing minimizes manual operations, reducing the burden on personnel. Without worrying about complex software settings or error handling, advanced analysis is completed simply by uploading the captured data. While processing is underway, on-site staff can proceed with other tasks, improving overall work efficiency. Using LRTK drone point clouds makes 3D surveying that used to take significant time remarkably faster, contributing to quick decision-making and shorter project delivery times. Furthermore, the cloud can process multiple projects concurrently, minimizing wait times.

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

Ensuring positioning accuracy in drone surveying is extremely important. As the name LRTK suggests, this service incorporates high-precision positioning based on RTK (Real-Time Kinematic) technology. RTK is a technique that reduces measurement errors to the centimeter level by adding correction information to satellite positioning such as GPS. LRTK uses RTK correction information via the cloud to provide high-precision position information to the photos acquired by the drone.

Specifically, using LRTK drone point clouds can greatly reduce the previously necessary work of installing GCPs. By precisely determining the camera position and shooting point coordinates using RTK, the resulting point cloud model is accurately positioned in the geographic coordinate system. The error that was on the order of several meters with standalone GPS can be improved to the order of several centimeters (several inches) by using RTK. This means that the acquired point cloud data will have minimal deviation when overlaid with existing drawings or GIS data. Reliable figures can be obtained for tasks such as creating survey maps and calculating earthwork volumes, so it can be used with confidence for design, construction planning, and as-built management. LRTK drone point clouds achieve public-survey-level high precision while providing a more accessible workflow than before.

Benefits of low cost and labor savings

One of the major advantages of introducing LRTK drone point clouds is cost reduction and labor savings. Traditionally, obtaining 3D survey data required large equipment investments and securing specialized personnel. For example, the purchase costs of laser scanners or RTK-capable drones, or licensing fees for photo processing software, were burdens on companies. Also, data processing and drawing production required experienced staff spending many hours, increasing labor costs.

However, by using LRTK’s cloud service, these initial investments and operational costs can be significantly reduced. With a commercially available aerial drone and a smartphone on hand, you can start the service without purchasing special surveying equipment. The analysis software is provided in the cloud, so there is no need to equip your company with expensive software. Since data processing is automated, there is no need to maintain specialized operators full-time; staff can obtain survey results while handling multiple roles with a small team. Also, by using a cloud service you always have access to the latest analysis technologies without the burden of updating software or maintaining hardware internally.

Moreover, because it is easy to use, you can perform surveys as needed, when needed. Surveys that were previously limited by cost can now be conducted frequently at low cost with LRTK. For example, it becomes realistic to record construction site progress weekly using drone point clouds. Labor savings allow field engineers to allocate time to other tasks, contributing to workstyle reform. In this way, LRTK drone point clouds realize affordable and low-effort 3D surveying, making them an easy-to-adopt solution 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.

• Surveying for civil engineering works: Rapidly surveying the current terrain of development sites or planned construction sites by drone to create 3D topographic maps for design. Also useful for as-built surveys after construction completion.

• Construction progress management: Regularly capturing construction sites by drone and comparing obtained point cloud data with previous data to visualize increases or decreases in earthwork and the degree of construction progress. Useful for creating objective records in reports.

• Earthwork and volume calculation: Automatically calculating excavation and fill volumes from point clouds to streamline quantity management. Tasks that were traditionally calculated manually can now yield accurate figures simply by specifying the area on the point cloud data.

• Infrastructure inspection: Capturing bridges, dams, slopes, and other infrastructure structures with drones to generate high-resolution point cloud models. Cracks and displacements can be measured on a desktop, and changes over time can be understood by comparing with past data.

• Disaster response and disaster prevention planning: Rapidly photographing landslide or flood sites by drone to generate point cloud models of the affected area. The volume of collapsed soil and inundation extent can be immediately grasped, serving as materials for initial response and restoration planning. During normal times, it also helps with regular monitoring of hazardous areas.

As described above, LRTK drone point clouds demonstrate their power across a wide range of applications, from construction and civil engineering to maintenance of social infrastructure and disaster prevention. Even in situations that were previously abandoned due to time or cost constraints, it will become easy to acquire 3D data and utilize it in operations.

Easy 3D surveying with LRTK

With the use of drones and cloud processing, 3D surveying has become more accessible and simple than ever. With LRTK drone point clouds, anyone can obtain precise three-dimensional data without specialized equipment. Even those attempting drone surveying for the first time can proceed smoothly with an intuitive smartphone app and automated processing.

The wave of 3D point cloud utilization is steadily spreading and will become an indispensable technology in future on-site digital transformation. Even companies or departments that have not yet introduced it, it is not too late to start with LRTK. Because it is low cost and low risk, you can begin with small-scale projects to experience its benefits. You will surely be surprised at the difference from conventional methods.

Harness the latest technology to bring efficiency and higher precision to your site. Open new possibilities in your work with LRTK’s easy 3D surveying.

Take your site to the next stage with LRTK.

FAQ

Q. What equipment is required to use LRTK drone point clouds? A. Basically, you can get started with a commercially available drone and a smartphone. Images captured by the drone can be uploaded to the LRTK cloud via a smartphone to generate point clouds. Even when high-precision positioning is required, there is no need to prepare expensive dedicated equipment (LRTK’s GNSS receiver devices or integration with existing RTK drones can be used as needed).

Q. Can it be used without prior drone surveying experience? A. Yes, LRTK is designed to be easy to use even for first-timers. Follow the instructions in the dedicated app to fly the drone and send the captured data to the cloud, and point clouds are generated automatically. Since difficult analysis is performed on the cloud side, operators do not need specialized knowledge. With about 5 minutes of on-site operation instruction, anyone can start 3D surveying that same day.

Q. What level of accuracy can be expected from the output point clouds? A. It depends on conditions, but by utilizing RTK positioning, accuracies on the order of several centimeters (several inches) can generally be expected. Even without installing ground control points (GCPs), LRTK’s RTK corrections improve the position of each photo, so the resulting point cloud model has high absolute accuracy. However, accuracy varies with flight altitude and satellite reception conditions, so for important measurements you should take care to fly with sufficient satellite coverage.

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

Q. How can the generated point cloud data be used? A. On the LRTK cloud, point clouds can be displayed in a 3D viewer to measure distances, areas, volumes, and create cross-sections. Point cloud data (LAS or PLY formats) and orthophotos can be downloaded for import into CAD or GIS software for design and analysis. You can also issue shareable links on the cloud to allow stakeholders to view the point cloud model via a browser and review it collaboratively. Acquired data can be reused for many purposes, generating significant added value from a single survey.

Q. How long does cloud processing take? A. It varies depending on the amount of data, but for example, processing is often completed within a few hours for a few hundred photos. Analyses that used to take a full day on a PC can be finished quickly in the cloud, so you may be able to check results on the same day you shoot. For very large projects, processing may take half a day to a day, but workers do not need to wait on-site; they will be notified as soon as results are ready for immediate review.