High-precision Drone Point Cloud Generation in the Cloud! How LRTK Is Changing Surveying Conventions

Table of Contents

• The spread of drone surveying and the use of point cloud data

• RTK-GNSS positioning is the key to higher precision

• Advantages of cloud-based point cloud generation

• What is LRTK? A new surveying method using smartphone × cloud

• Possibilities opened by simple surveying with LRTK

• FAQ

The spread of drone surveying and the use of point cloud data

In recent years, drone surveying has rapidly spread across construction and civil engineering sites. The method of flying an unmanned aerial vehicle (UAV) from the sky to capture terrain and structures provides data and has major advantages over traditional ground surveying: it can cover wide areas in a short time while offering higher safety and efficiency. In fact, there are reports where surveying a vast site that would have taken several days using a total station and teams on foot was completed in less than half a day with drone aerial photography. Also notable is that drones can safely capture conditions from above in areas people cannot enter, such as steep slopes or disaster sites.

Data captured by drones can be used to produce a variety of deliverables through post-processing. For example, orthophotos—images stitched from aerial photos that provide distortion-free, map-like views from directly above—are useful for overall site overviews and progress management. Further, point cloud data generated by analyzing drone photos (photogrammetry) is 3D data that precisely reproduces terrain and building surfaces as a collection of countless points. Using these point clouds, you can understand ground elevation distributions, accurately calculate earthwork volumes, and create cross-sections or 3D models, enabling a wide range of analyses. Drones are thus powerful tools for digitizing entire sites, and initiatives promoted by the Ministry of Land, Infrastructure, Transport and Tourism, such as "i-Construction", are driving the increasing importance of 3D data utilization in the construction industry.

However, although drones enable broad-area data acquisition, ensuring the accuracy of that data has become a challenge. No matter how easy it is to digitize, if position or dimensional errors are large, the data cannot be used as official survey results. This has led to the emergence of technologies and services that enable high-precision positioning. The representative example is RTK-GNSS positioning described next, which is enabling drone surveying to evolve into not just fast but also accurate surveying.

RTK-GNSS positioning is the key to higher precision

A key technology attracting attention recently for achieving high-precision drone survey data is RTK-GNSS (Real-Time Kinematic GNSS). RTK is a technique that performs satellite positioning simultaneously at a base station (a GNSS receiver installed at a reference point) and a rover (a GNSS on the drone), and real-time corrects the positional difference between them to dramatically improve positioning accuracy. Whereas normal GPS positioning can have errors on the order of several meters (several ft), RTK can reduce errors to within a few centimeters (a few in). Equipping a drone with a high-precision RTK-capable GNSS allows the vehicle to receive correction information during flight and record its exact position. As a result, the positional accuracy of captured images and acquired data is greatly improved, and point clouds and orthophotos generated in post-processing align with map coordinate systems at high precision.

There are many benefits to high-precision drone surveying using RTK. First, photogrammetric accuracy improves, allowing a drastic reduction in the number of ground control points (GCPs) placed on the ground. Traditionally, to create precise 3D models from drone photos, multiple reference points needed to be surveyed in advance and appear in the photos so the model could be corrected in post-processing. However, with RTK-capable drones, the positional information recorded for each photo itself can be accurate to within a few centimeters (centimeter-level accuracy (half-inch accuracy)), so in some cases you can meet required accuracy with zero ground control points. Field reports say that introducing RTK drones eliminated the labor of placing GCPs and significantly shortened survey preparation time. Despite this simplification, the resulting point clouds and photos are highly precise, streamlining as-built checks, quantity calculations, and progress management.

Second, overall survey efficiency improves and costs are reduced. RTK drones not only reduce laborious preparation but also fly precisely via automated flight, reducing the need for re-shoots or re-flights. In favorable weather, the planned area can be photographed in a short time in a single flight, allowing survey personnel to move immediately to their next tasks after data acquisition. There are cases where field surveys that used to take half a day were completed in about an hour, producing significant savings in labor and equipment costs. Additionally, because the drone-mounted GPS yields high-precision positions in real time, operators can immediately re-fly to capture an additional point if needed. Overall, upgrading to fast and precise surveying is likely to dramatically improve on-site productivity.

Third, the reliability of acquired data is improved. Point clouds and orthophotos with errors suppressed by RTK corrections have quality that can be confidently used for public inspections and drawing creation. For example, if as-built management maintains accuracy within a few centimeters (within a few in), explanations to clients become smoother, and additional ground surveys may sometimes be avoided. High-accuracy data can also withstand comparison and verification against design data in later processes, enabling faster decision-making based on survey results. RTK is thus a technology that transforms drone surveying into surveying that is not just fast but also accurate and reliable.

To use RTK positioning on site, a GNSS receiver to serve as the base station and a means to deliver its correction information to the rover are required. You can set up your own base station, but in Japan it is common to use network RTK services (VRS and similar) provided by carriers like NTT or the Geospatial Information Authority of Japan to obtain correction data over the Internet. Recently, even in mountainous areas outside cellular coverage, it has become possible to perform RTK positioning using the centimeter-class augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite “Michibiki.” With the development of such infrastructure, environments that can stably provide cm-level positioning anywhere on site are becoming established.

Advantages of cloud-based point cloud generation

Generating point clouds and 3D models from the high-resolution photos captured by drones requires processing called photogrammetry. This process aligns large numbers of images by feature matching and reconstructs 3D shapes, requiring very advanced computation. Traditionally, this meant installing specialized software on a high-performance PC and processing for hours to days. Obtaining point clouds or detailed 3D models for large construction sites could require high-spec PCs in-house and staff experienced in analysis, which can be costly.

As a solution to these challenges, cloud-based point cloud generation services have attracted attention in recent years. With cloud photogrammetry services, you simply upload many photos taken on site via the Internet, and servers automatically generate point clouds and models. Users do not need their own high-performance machines; they can request processing and view results from a regular PC or tablet via a browser. Because the cloud provides the latest algorithms and large-scale computing resources, processing time tends to be shorter and very dense point clouds can be generated efficiently.

The advantages of cloud-based point cloud processing do not end there. Generated point clouds and 3D models are stored in the cloud, making it easy to share data with stakeholders inside and outside the company. For example, if a field representative flies a drone in the afternoon and immediately runs cloud processing, engineers in a distant office can view the completed point cloud and orthophotos by evening. This allows internal tasks such as volume calculations and drawing creation to begin on the same day without waiting for someone to copy data to a USB drive. With data in the cloud, real-time collaboration becomes possible and the speed of information transfer between the field and office dramatically improves.

Storing data in the cloud also simplifies past survey data management. Upload histories are kept by date and site name, so if you want to review last year’s point cloud, you can log in to the cloud and retrieve it easily. Compared to paper records or local PC storage, the risk of loss or data corruption is reduced. Some services also offer functions to perform simple point cloud analyses, create cross-sections, or add comments directly in the cloud. Even without specialized software on hand, data use can be completed in a browser, significantly changing work flows.

Overall, the combination of cloud and drone point cloud generation is an ideal solution for handling high-precision, large-scale 3D data. From on-site data capture to processing and sharing, the workflow becomes smoothly integrated, greatly speeding up delivery of survey results that used to take days. Lowered barriers from cloud utilization mean that companies increasingly handle surveying tasks in-house that they previously outsourced to specialists. The next chapter introduces an innovative solution that makes cloud point cloud generation even more accessible: LRTK.

What is LRTK? A new surveying method using smartphone × cloud

As described above, combining drones, RTK, and cloud processing enables efficient acquisition of high-precision 3D survey data. However, when trying to operate this in the field, you might worry, “Do I need an expensive RTK-equipped drone or dedicated equipment?” LRTK was developed to lower such hurdles at once and make high-precision surveying easily accessible to anyone. LRTK is an integrated solution developed by a startup from Tokyo Institute of Technology, consisting of a small RTK-GNSS receiver, a smartphone app, and a cloud service. In short, it transforms a smartphone into a high-precision surveying instrument and manages and utilizes the acquired data in the cloud—realizing a new surveying style.

The small receiver at the heart of LRTK is pocket-sized at about 150 g and houses a multi-band, high-performance GNSS module. It is designed to attach to a smartphone or tablet with a single touch. Attaching this to your phone upgrades the phone’s GPS—which normally has errors of several meters (several ft)—to centimeter-level accuracy. The device is a dedicated case-type unit with no wiring, runs on an internal battery, and requires no complicated setup. The moment you attach the LRTK device to your phone, the smartphone that was used only for map apps becomes a “universal surveying instrument,” ready to be used on site.

So what specific surveying and measurement tasks can LRTK perform? First is high-precision position measurement. By tapping a button on the smartphone screen at the point to be measured, you can instantly record the latitude, longitude, and height of your current location. RTK corrections keep errors to within a few centimeters (centimeter-level accuracy (half-inch accuracy)), allowing anyone with a tap to obtain accuracy comparable to reference point surveys that previously required specialized instruments and skilled personnel. The app also has functions to automatically average positioning data to improve accuracy; by standing still and measuring for several tens of seconds, you can obtain stable coordinates on the order of millimeters. This potential enables advanced surveying tasks such as establishing construction reference points and displacement monitoring.

Another notable capability is digital measurements such as point cloud capture. LRTK works with the smartphone camera and various sensors to record site conditions as 3D data. For example, if you walk around a site with a smartphone and capture photos, a high-precision 3D point cloud model can be generated from the movement trajectory and images. Point cloud measurements that once required expensive laser scanners can now be easily achieved with just LRTK and a smartphone. Distances, areas, and volumes can be measured from the acquired point clouds, and as-built checks can be performed by overlaying CAD design data—smoothly handled in the cloud. LRTK also supports a “LRTK drone” workflow: you can upload drone aerial photos to the cloud for point cloud generation. Even if you only have a consumer drone without RTK, if the LRTK device has collected GNSS data at ground reference points on site, you can correct photo geotags afterward to generate high-precision point clouds. The ability to achieve high-precision survey results with inexpensive airframes by combining them with LRTK is a major advantage.

It is also important that LRTK is integrated with a cloud service. Coordinate and point cloud data acquired on site can be uploaded to the LRTK cloud with one button from the smartphone. From the moment data is uploaded, it can be shared with other team members, and office PCs can immediately view and start analyzing the data. For example, if you send a point cloud captured with LRTK from the field to the cloud, office staff can view it in real time and begin necessary measurements or drafting. Real-time coordination between the field and office eliminates wasted waiting time and greatly improves work speed. Data stored in the cloud is organized by date and project, making it a valuable survey archive for future reference.

In this way, LRTK—by combining a small device, smartphone, and cloud—opens the world of high-precision surveying, once limited to specialists, to general engineers. Its presence can truly be said to be changing the “conventional wisdom of surveying” on the jobsite.

Possibilities opened by simple surveying with LRTK

Finally, let us touch on the new possibilities brought by LRTK’s “simple surveying.” Simple surveying with LRTK is the concept of enabling anyone to carry out centimeter-accurate surveys routinely without complicated equipment operation or specialized knowledge. With LRTK’s compact RTK-GNSS terminal and smartphone app, heavy tripods and complex settings are unnecessary. For example, a young engineer whose specialty is construction management can take a smartphone with LRTK from their pocket, complete survey preparation in minutes, and quickly measure and record coordinates for the required points. There are reports that terrain surveys which previously required a team and a full day were completed in minutes with a smartphone scan using LRTK, eliciting surprise from field teams.

Realizing simple surveying means that small measurement tasks previously outsourced to specialized surveyors can be handled in-house, and routine progress checks and as-built inspections can be performed frequently with high accuracy. For instance, if someone on site wants to know the approximate distance from here to there immediately, LRTK can measure it on the spot and share the results. In disaster response, LRTK can be powerful for emergency measurement of damaged areas and quick provision of data to stakeholders. In urban surveys where drones cannot be flown, walking surveys with LRTK to collect point clouds are an alternative method, broadening possible use cases. Tasks once thought to require specialists, time, and cost are becoming “work anyone can do anytime, anywhere” with LRTK.

As a solution that enables cloud-based high-precision drone point cloud generation, LRTK’s simplicity strongly supports on-site digital transformation (DX). Lowering the surveying barrier makes it easier to frequently digitize site conditions and feed data back into construction and quality management, which in turn directly improves overall site productivity and quality assurance. If your workplace has the mindset “we leave surveying to the specialist department” or “we don’t handle detailed 3D data at our site,” consider trying LRTK’s new simple surveying. You will likely feel how surveying conventions can truly change.

FAQ

Q1. Do I need specialized knowledge to generate point clouds from drone photos? A. As long as you understand the basic procedures, you can generate point clouds without deep specialist knowledge. Tools such as cloud photogrammetry services and solutions like LRTK allow you to upload photos and press a button to automatically generate point clouds. There are practical tips—for example, ensuring full coverage of the site without gaps and obtaining an appropriate overlap rate between images—but AI-supported apps that assist in flight and shooting plans have appeared, making it easier for beginners to get started.

Q2. Can high-precision surveying be done with a drone that is not RTK-capable? A. Yes. For non-RTK drones, post-processing kinematic (PPK) methods are commonly used to improve accuracy. For example, you can operate a GNSS receiver (such as an LRTK device) on the ground during the drone flight to record observation data and later correct the drone photo geotags. You can also place several known ground control points and align the model to those points after point cloud generation to improve accuracy. Using LRTK makes it easy to acquire reference point data in a simple way, which helps verify and correct point clouds obtained from non-RTK drones.

Q3. Are data volume and security OK when processing point clouds in the cloud? A. Drone photos and point cloud files can be large, so you should choose a cloud service plan that supports large data volumes. However, recent improvements in network environments and cloud-side optimizations mean that large data uploads and processing are relatively smooth. Regarding security, many services implement encryption in transit, access control settings, and data center security measures. In most cases, the security level is comparable to managing your own servers. If you are concerned, check the service provider’s security policy and track record.

Q4. What types of sites is LRTK used at? A. LRTK is being used across a wide range of sites: construction and civil engineering site management and as-built surveying, infrastructure inspections, disaster situation assessment, and agricultural field management. For example, at a dam construction site, weekly 3D terrain models were created with LRTK and drones to manage excavation volumes and visualize progress. Local governments have reported cases where staff used LRTK to create 3D records of damaged areas during disasters and used them to quickly formulate recovery plans. Because LRTK is compact, portable, and does not require specialized skills, it is valued for its “mobility to measure immediately when needed” regardless of the site.

Q5. How can I introduce LRTK? A. If you are interested in adopting LRTK, you can contact the vendor or request materials from the official website. You can receive information about detailed specifications, pricing, use cases, and support for implementation. Demonstrations are often held at exhibitions and seminars nationwide, so trying it hands-on is a good option. Some vendors offer trial loans before purchase, allowing you to evaluate whether it fits your operations before making a formal decision. LRTK proposes a new surveying style, so please consider it positively.