Drone × LRTK for Wide-Area Surveys! Latest Point Cloud Utilization Techniques for Land and House Surveyors

Introduction

In recent years, advances in drones (unmanned aerial vehicles) and high-precision GNSS positioning technologies have dramatically evolved surveying methods. For professionals involved in surveying, including land and house surveyors, using these cutting-edge technologies for wide-area field surveys has become faster, more precise, and safer and more efficient than conventional approaches. In particular, combining point cloud data (collections of numerous measured points) obtained from aerial photogrammetry with centimeter-level correction technologies such as RTK and LRTK makes it possible to accurately capture the terrain and structures of large tracts of land in a short time.

This article explains the characteristics and benefits of acquiring point cloud data through drone aerial photography, provides an overview of GNSS RTK and LRTK technologies that enable high-precision positioning, and describes concrete practical applications for land and house surveyors. It also covers deliverables that can be generated from point cloud data and their practical value, the efficiency and safety improvements gained by adopting the latest technologies, and concludes with how simple surveying using LRTK can assist wide-area surveys and improve point cloud accuracy. Consider this a guide to understanding the latest surveying technologies and applying them in your daily work.

Acquiring Point Cloud Data by Drone Aerial Photography and Its Characteristics

In photogrammetry using drones, terrain and structures are photographed from the air as numerous images, and specialized software analyzes these images to generate high-density 3D point cloud data. Because data can be collected from the air over areas, wide-area site conditions that would take a long time to survey by ground crews can be captured in a short period. For example, in surveys of forests or large planned development sites, drone aerial photography can acquire point clouds of the entire terrain, allowing heights and distances at arbitrary locations to be measured later at a desk. This can dramatically improve the efficiency of large-scale field surveys that previously took days to weeks.

Point cloud data obtained from drone photogrammetry has the following features and advantages:

• Rapid data acquisition: Since a wide area can be photographed from the air at once, on-site condition data for large lands can be acquired in a short time. Surveys can be conducted safely by remote operation even in dense forests, steep slopes, or disaster sites where people cannot enter. Tasks that previously required several days can sometimes be completed in a few hours to half a day, directly shortening overall project schedules.

• High-precision measurement: Drones are equipped with high-resolution cameras and positioning devices, and coordinates of each point can be derived from the images with centimeter-level precision. Structure from Motion (SfM) analysis using many photos can generate detailed 3D models and precise orthophotos that faithfully reproduce the terrain. Because data with accuracy comparable to conventional ground surveys can be obtained, these results can be used as highly reliable surveying deliverables.

• Improved cost efficiency: A single flight can cover a wide area, greatly reducing the need for personnel deployment and the installation of many control points. On large sites, completing the survey with a small crew in a short time can significantly reduce costs, including labor. Tasks that used to take weeks by manual methods—such as earthwork volume calculations and land surveys—can be shortened to days using a combination of drones and analysis software.

• Enhanced safety: With drone surveys, data can be collected remotely in hazardous areas such as cliffs, valley bottoms, or around buildings at risk of collapse—places where people entering would be dangerous. Even locations that are “needed to be measured but cannot be approached” can be fully captured, greatly improving on-site safety.

Drone-based point cloud surveying can be a major asset for land and house surveyors. However, note that drone battery life is limited; surveying extremely wide areas may require multiple flights or battery swaps. Additionally, regulatory constraints such as aviation laws may limit flight zones and times, and in some conditions a pilot license may be required. Nevertheless, with proper planning and technology, drone point cloud surveying can complement or replace traditional methods as a powerful option.

GNSS Positioning and High-Precision Corrections Using RTK and LRTK

To tie point cloud data acquired from drones or on the ground to accurate coordinate positions, high-precision position information from GNSS positioning (Global Navigation Satellite Systems) is essential. GNSS includes satellite positioning networks such as the U.S. GPS, Russia’s GLONASS, and Japan’s Quasi-Zenith Satellite System "Michibiki." Standalone GNSS positioning typically results in errors on the order of meters due to signal reflections and atmospheric effects. This is why smartphone or car navigation GPS can be off by about 5–10 meters, which is insufficient for defining land boundaries or for precision surveying.

What addresses this is RTK (Real Time Kinematic), a real-time positioning correction technology. RTK uses two GNSS receivers—a base station and a rover—where the base station at a known coordinate sends error information to the rover, correcting its position and dramatically improving positioning accuracy in real time. Concretely, the base station’s error estimates are shared via radio or the internet, and the rover (a drone or receiver) applies corrections to its measured position, reducing errors to a few centimeters (typically 2–3 cm horizontally and a few centimeters vertically). RTK achieves centimeter-level accuracy by using the carrier phase of satellite signals, aligning the integer number of wavelengths.

Recently, services that distribute correction information using the Geospatial Information Authority of Japan’s reference station network, and Japan’s Michibiki centimeter-level augmentation service (CLAS), have created environments where users can obtain RTK correction data without setting up their own base stations. One example is the latest high-precision positioning solution called LRTK. LRTK combines a compact high-precision GNSS receiver with a dedicated app/service to make RTK positioning easily available using just a smartphone. LRTK-compatible receivers attach to a smartphone and receive correction data via Bluetooth or the internet to provide real-time high-precision coordinates to the phone. They also support CLAS signals from Japan’s QZSS, enabling satellite-based corrections that can maintain centimeter accuracy even in areas without cellular coverage—such as mountainous regions.

By using RTK and LRTK, point cloud data acquired by drones and surveying data collected with smartphones can be linked to accurate geodetic coordinates. In other words, by giving the detailed point clouds obtained over wide areas a high-precision positional reference, survey results that conform to map coordinate systems can be produced. For land and house surveyors, these positioning correction technologies are powerful tools that markedly increase the reliability of boundary measurements and drawing creation.

Practical Examples of Drone Point Cloud Usefulness for Land and House Surveyors

Combining drone point cloud surveying with RTK/LRTK high-precision positioning has major impacts across the various tasks handled by land and house surveyors. Below are representative use cases.

Use in Existing-Condition Surveys

For existing-condition or topographic surveys conducted as a basis for development plans and land use studies, drone point clouds are highly effective. Because they can accurately capture wide-area terrain and existing structures, they dramatically streamline surveys that previously took days for planimetric and elevation measurements. Existing-condition drawings generated from the obtained 3D point clouds reflect terrain relief, vegetation, and building layouts in detail, providing more persuasive materials to planners and clients. Also, if you store the raw point cloud data, additional measurement items requested later can often be handled at the desk without re-surveying, reducing the need for follow-up fieldwork.

Assisting Boundary Surveys and Boundary Determination

Drone utilization also plays an auxiliary role in confirming boundary points and in boundary determination work. Legal procedures such as installing boundary markers and conducting joint inspections with adjacent landowners are still necessary, but aerial images and point cloud data from drones enable a bird’s-eye understanding of terrain, structures, and vegetation near boundaries. This makes it easy to create detailed orthophotos showing the relationship between boundary lines and surrounding features, helping stakeholders reach a common understanding of boundary positions. Overlaying measured boundary point coordinates onto point clouds allows three-dimensional verification of boundary straightness and elevation differences with adjacent land, improving the accuracy of boundary determination plans. Hard-to-access boundary marker areas can be observed from the air, reducing the burden of on-site checks for surveyors.

Use in Preparing Materials Before Earthwork/Development Design

It is critically important to prepare detailed terrain data before designing housing developments or other earthworks. By providing high-resolution point clouds and orthophotos captured by drone as existing-condition data, land and house surveyors enable designers and civil engineers to inspect a three-dimensional model of the site from the office. For instance, in earthwork planning, contour maps and longitudinal profiles generated from point clouds help determine how much cut-and-fill is required. Terrain features and drainage paths that previously relied on ground surveys and field inspection are comprehensively modeled in point cloud data, increasing the precision of design-phase considerations. Sharing these detailed materials in advance helps prevent rework in design and optimizes construction planning.

Deliverables Generated from Point Cloud Data and Their Practical Value

Point cloud data obtained by drone aerial photography or mobile surveying not only has intrinsic value as a 3D coordinate set but can also be processed and analyzed to produce a variety of deliverables. Representative outputs useful in the work of land and house surveyors and related fields include the following:

• Orthophotos: Composite images produced by stitching together many drone photos and applying geometric correction to produce a true overhead photographic map. Orthophotos correspond accurately to map coordinates at every point, enabling distance and area measurements. When overlaid with boundary lines or survey maps, orthophotos are extremely useful for understanding site conditions and preparing explanatory materials.

• DSM/DTM (Digital Surface Model / Digital Terrain Model): Elevation data extracted from point clouds representing surface heights. A DSM (Digital Surface Model) includes buildings and vegetation on the surface, whereas a DTM (Digital Terrain Model) removes those features to represent bare-earth terrain. These models enable assessment of elevation differences, slopes, and drainage, and are used for earthwork volume calculations, development planning, and flood simulations.

• Cross-sections and longitudinal profiles: By drawing an arbitrary line on point cloud data, cross-sectional shapes along that line can be generated. Creating cross-sections for roads, rivers, or planned development sites aids in evaluating cut-and-fill, designing retaining walls, and checking elevation relationships with surrounding land. If you have point clouds from multiple times, pre- and post-construction terrain changes can be compared with cross-sections for installation inspections.

• 3D models: Point clouds can be converted into polygon meshes and textured with photographs to create realistic three-dimensional models. Modeling buildings and structures supports drawing preparation for registration, cultural property records, and landscape simulations, among other uses. With the growing adoption of BIM/CIM, demand for using 3D data in design and construction processes is increasing.

These deliverables provide visual clarity and detailed information that traditional 2D drawings cannot. In the work of land and house surveyors, for example, presenting orthophotos during boundary explanations or using contour maps and cross-sections derived from point clouds as attachments for development permit applications are scenarios where point cloud–derived deliverables add value.

Efficiency Gains and Safety Improvements from the Latest Technologies in Surveying Work

The combination of drones × point cloud utilization and RTK/LRTK high-precision positioning brings significant benefits to land and house surveyors in terms of both efficiency and safety improvements.

On the efficiency side, shortening fieldwork time and shifting work to the office are key advantages. Because wide-area surveys can be completed quickly, the time surveyors spend traveling or installing control points is reduced. Analyzing point clouds in software makes it possible to derive necessary measurement items (distances, areas, elevation differences, etc.) later, so there is no need to stay on-site for extended periods to avoid "forgetting" to measure something. Since everything is recorded digitally, additional requests or design changes can often be addressed by reanalyzing the data rather than revisiting the site. Point clouds and orthophotos are also easy to share and review online with stakeholders, streamlining meetings and supporting business continuity through remote work.

Regarding safety improvements, the biggest point is reducing entry into hazardous areas, as mentioned earlier. In high places, on soft ground, or in disaster-stricken areas where people could be harmed, drones combined with high-precision positioning allow safe data collection from a distance. Reducing worker burden and lowering the risk of accidents or injuries is also a major benefit for corporate safety management. Furthermore, automation and digitization of data measurement reduce human errors and help standardize quality. For example, small discrepancies that occur when multiple people measure the same point can be eliminated when measurements are taken on a point cloud, yielding identical results regardless of the operator. This improves reproducibility and reliability of survey outputs, making quality assurance easier during inspections and delivery.

Conclusion: A New Era of Wide-Area Point Cloud Surveying Opened by LRTK

Wide-area point cloud surveying using drones and position correction technologies provided by high-precision GNSS are creating new possibilities for land and house surveyors. Among these, the emergence of LRTK, which enables centimeter-level positioning with a smartphone and a compact device, is a revolutionary solution that combines "ease of use" with "improved accuracy." By adopting LRTK, RTK-level surveying that used to require expensive specialized equipment and advanced expertise can be implemented more accessibly, greatly aiding precision control for wide-area drone surveys and simplifying cadastral surveys.

For example, georeferencing point clouds acquired by drones can be performed with high accuracy by using several known points measured with LRTK as references. Moreover, even on very large sites, LRTK can maintain centimeter-level accuracy by receiving satellite augmentation signals in areas without cell coverage, enabling consistent high-precision surveying anywhere. As a result, tasks that were previously constrained by difficult positioning environments—such as boundary surveys in mountainous regions or infrastructure inspections—can now be executed efficiently with high-precision data collection.

Going forward, ICT surveying technologies such as drones × LRTK will continue to advance and support the role of land and house surveyors. Actively incorporating the latest point cloud utilization techniques will not only improve operational efficiency and service quality but also enhance the ability to handle new projects and differentiate your services. By combining traditional surveying techniques with the latest technologies, you can create greater value in future surveying work.