Easy Introduction to Improve On-site Work Efficiency! Recommended RTK Receivers

Table of Contents

• Background: Why earthwork volume calculation and point cloud data utilization are drawing attention

• The importance of positioning technology that determines point cloud accuracy

• What is RTK? Basics and types of receivers

• Why RTK receivers are effective for earthwork volume calculation and as-built management

• Characteristics of RTK receivers that are easy to introduce (compact, smartphone-linked, all-in-one, etc.)

• Case studies of sites that introduced them (labor saving, same-day results, improved accuracy, etc.)

• Implementation steps and selection points (excluding price information)

• Practical workflow for obtaining point cloud control points via smartphone surveying using LRTK

• Use cases on site (stake setting, photogrammetry, AR navigation, volume calculation)

• Conclusion: Prospects for efficiency and high-precision management with RTK receivers

• FAQ: Frequently asked questions about RTK receivers, positioning accuracy, point cloud data integration, etc.

Background: Why earthwork volume calculation and point cloud data utilization are drawing attention

In construction and surveying fields, earthwork volume calculation and the use of 3D point cloud data have been attracting significant attention in recent years. This trend is driven by the spread of ICT technologies promoted by initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction,” and the need to improve productivity in response to a shortage of experienced workers. Traditionally, progress management and earthwork volume calculation for earthworks required cross-section surveys on site and manual calculations, which consumed considerable time and effort. However, with the advent of drone photogrammetry and 3D laser scanners, terrain can now be recorded in detail as point cloud data and volumes can be calculated digitally. In addition, by using LiDAR scanners built into smartphones and tablets, anyone can easily perform 3D scanning on site. As a result, it is becoming the “new normal” to precisely capture terrain changes before and after construction and carry out earthwork volume calculations and as-built (finished geometry) verification.

Point cloud utilization has become a game changer particularly for earthwork volume calculation. Previously, people measured heights at fixed intervals to create cross-sections and calculated volumes using the average-end area method. This approach required a lot of work and risked missing local terrain changes. By contrast, using point clouds from drone photos or laser scanners allows the ground surface to be recorded in detail and volumes to be calculated accurately from those differences. Once point cloud data are obtained, recalculating volumes for different areas can be done without additional surveying. In fact, in a case at a major construction company, earthwork surveying and calculation that had taken four people seven days was completed by two people in one day after switching to drone photography and point cloud processing. The accuracy of volume calculations using point clouds has been confirmed on site to be comparable to conventional methods (errors around 1%). Thus, the introduction of point cloud data significantly reduces work time and manpower while capturing as-built quantities with sufficient accuracy, increasing its importance.

The importance of positioning technology that determines point cloud accuracy

Accurate use of point cloud data depends critically on the positioning technology used during surveying. No matter how dense a point cloud is, if it is not placed in the correct site coordinate system, comparisons with design drawings and volume calculations will produce errors. For example, drone photogrammetry can generate high-precision point clouds from captured images, but if the position information (geotags) assigned to each point is inaccurate, the data cannot provide the precision required for as-built management. Therefore, conventionally, GNSS surveying was used to set control points, and a georeference (coordinate alignment) process was performed to correct point cloud data to that reference.

Typical smartphones or consumer GPS devices provide position accuracy on the order of several meters at best, which is unsuitable for precision civil surveying. On the other hand, among satellite positioning technologies, the RTK method (Real-Time Kinematic) can obtain position coordinates with errors on the order of centimeters. In other words, by providing point clouds with position information obtained via RTK, the entire point cloud dataset can be placed in a high-precision coordinate system. This enables advanced digital construction management, such as accurately detecting discrepancies between design 3D data and point clouds in as-built management, and strictly comparing multiple survey datasets to understand increases or decreases in earthwork volume. To maximize point cloud accuracy, it is essential to combine high-precision positioning technologies such as RTK, and its importance has been increasingly recognized in recent years.

What is RTK? Basics and types of receivers

RTK (Real-Time Kinematic) is a positioning technique that uses signals from GNSS satellites, including GPS, to correct positioning errors in real time and achieve centimeter-class accuracy. The basic mechanism involves a base station placed at a known location and a rover that measures while moving; both receive satellite signals simultaneously, and the error information computed at the base station is sent to the rover to realize high-precision relative positioning. Standalone GPS positioning can have meter-level errors due to atmospheric effects and satellite orbit errors, but RTK corrects these to reduce errors to within a few centimeters.

There are several types of RTK receivers. Traditionally, high-performance fixed antennas combined with dedicated controllers were used as base station/rover sets. However, network RTK—using the Geospatial Information Authority’s reference point network or private correction services over the internet—has become widespread, and cases where a standalone rover receiver can perform positioning have increased. Advances in technology have also led to the miniaturization and cost reduction of receivers, with handheld and smartphone-integrated RTK receivers appearing. For example, where large fixed equipment, long antennas, and UHF radios were once required, today there are products that achieve RTK positioning simply by attaching a palm-sized antenna to a smartphone. Receivers range from high-precision dual-frequency units to single-frequency L1 units that reduce cost; choosing according to on-site usability and required accuracy is important.

In Japan, as a means of obtaining correction signals, the Quasi-Zenith Satellite System “Michibiki” provides a Centimeter-Level Augmentation Service (CLAS). RTK receivers compatible with CLAS can perform RTK positioning using signals from Michibiki satellites even in sites where internet connectivity is difficult, such as mountainous areas. As environments where positioning is possible without deploying a base station become more established, the barrier to RTK adoption has fallen significantly compared to the past.

Why RTK receivers are effective for earthwork volume calculation and as-built management

Introducing RTK receivers dramatically improves the efficiency and accuracy of earthwork volume calculation and as-built management in civil engineering. There are several reasons for this.

First, improved measurement accuracy. RTK enables centimeter-level positioning that is impossible with handheld GPS, providing high reliability to the acquired point cloud and survey point data. For example, if ground elevations before and after excavation or embankment are measured with RTK, volumes calculated from those differences are highly accurate. Volumes that were previously approximated using cross-sectional methods can be calculated directly from high-density point clouds obtained with RTK, yielding results with minimal discrepancies during on-site verification.

Next, improved work efficiency. With RTK receivers, a single worker can survey many points in a short time. Historically, as-built height measurements required levels or total stations and at least two people; RTK GNSS allows a single operator to cover wide areas without needing an assistant or a rod holder. Because positioning results are available in real time, ground elevations and structure locations can be checked on the spot, making it possible to immediately identify discrepancies from the design. This enables same-day checks such as “Are all embankments at the design height?” or “Is the roadbed shape correct?” and to issue instructions for additional filling or grading as needed.

Furthermore, digital data integration is a major advantage. Point data obtained with RTK receivers are recorded in a unified coordinate system for plan and elevation, allowing direct import into CAD drawings or CIM models. Survey data from multiple days can be compared against the same reference, enabling quantity-based progress management and creating as-built heat maps for quality assessment. Recently, combining RTK positioning with tablet devices allows point cloud data acquired on site to be shared with the office via the cloud instantly, so all stakeholders can make decisions based on the same up-to-date data. Adopting RTK receivers thus not only ensures quality through accurate measurement but speeds up the entire process from surveying to analysis and sharing, serving as a key driver for on-site DX (digital transformation).

Characteristics of RTK receivers that are easy to introduce (compact, smartphone-linked, all-in-one, etc.)

Modern RTK receivers incorporate numerous features to make on-site implementation easier. Below are particularly notable characteristics.

• Compact and lightweight design: Recent RTK receivers are very compact, with some fitting in a pocket. They can weigh around 100g and come with dustproof and waterproof ratings, making them easy to carry and rugged for field use. Because there is no need to carry a traditional fixed antenna or large battery pack, the physical burden of work is greatly reduced.

• Smartphone linkage: Increasingly, RTK receivers can connect to smartphones or tablets via Bluetooth or cable and be operated through dedicated apps. This allows positioning tasks to be completed using a familiar smartphone screen without an expensive dedicated controller. With a simple “start positioning” button in the app, coordinates are automatically acquired and plotted on a map, making the intuitive UI accessible even to beginners. Using the smartphone’s communication capabilities to connect to correction services over the internet (Ntrip, etc.) enables many users to begin RTK positioning without dealing with complicated settings.

• All-in-one functionality: “All-in-one” refers to end-to-end handling from positioning to data management. Modern RTK receivers and compatible apps can automatically convert acquired coordinate data into a specified coordinate system (e.g., the plane rectangular coordinate system, ◯ zone) and elevation system (geoid height, etc.) and record it. Users can add names, notes, and link photos to each point for consolidated on-site data management. Many devices also integrate with cloud services, allowing field data to be uploaded to a server immediately for internal sharing. Such all-in-one workflows eliminate post-survey data organization and transcription errors and shorten the time from surveying to reporting.

• Easy setup: To lower adoption barriers, many RTK receivers feature simplified initial setup and on-site installation. Examples include built-in batteries for long operation without power cables, one-touch mounts for quick attachment to smartphones, and attachments that allow a monopod to serve as a leveling staff. These features shorten the time from arrival on site to starting positioning and make it easy for anyone to begin measurements immediately.

Examples of the latest RTK receivers with these features (such as smartphone-integrated “LRTK” series) are attracting attention from field personnel as “easy-to-introduce, easy-to-use RTK.” Because they can be used without special skills, personnel other than survey specialists can utilize high-precision positioning in daily operations.

Case studies of sites that introduced them (labor saving, same-day results, improved accuracy, etc.)

Sites that have introduced RTK receivers report various benefits. Below are some representative cases and effects.

• Labor saving and improved safety: In a municipal disaster recovery site, a smartphone-linked RTK receiver was used to survey a collapsed slope. A single worker was able to measure the unstable slope from a safe, distant location and obtain the necessary point cloud data, minimizing personnel and avoiding hazardous entry. Tasks that previously required a survey team of multiple people were completed by one person, improving safety by reducing site entries. In another case, reducing the manpower needed for control point surveying enabled parallel execution of other tasks, shortening the overall construction period.

• Same-day deliverables: In a case combining drone photogrammetry and RTK receivers, aerial photos taken in the morning were processed into point clouds and volumes in the afternoon, allowing same-day reporting to the site representative. Because coordinates obtained with RTK were accurate, no additional positional adjustments were required for point cloud models generated from photos, enabling fast volume calculations. Receiving deliverables the same day allowed timely on-site decisions, such as “We are short by ◯ m³ from today’s excavation plan, so increase tomorrow’s filling,” enabling quick schedule adjustments.

• Improved accuracy and quality assurance: In road construction as-built management, introducing RTK improved checks of paving thickness and roadbed elevation. By comparing point clouds with design 3D models and creating color-coded heat maps of elevation differences across the finished surface, localized areas of insufficient thickness that would have been missed were discovered. Such detection was made possible by RTK’s high-precision alignment, allowing immediate on-site correction to meet quality standards. Thus, the use of RTK receivers has been praised on site not only for shortening survey time but also for raising construction quality through more reliable measurement data.

• Data sharing and remote supervision: One construction company uses RTK receivers and the cloud to share survey data instantly. When field staff upload as-built point clouds collected with tablets and RTK receivers to the cloud, supervisors and clients in the office can view the data almost in real time. This enables partial implementation of remote construction management, where as-built checks and instructions can be given without being physically present. For managers overseeing multiple distant sites, the ability to accurately understand site conditions while reducing travel time is a major advantage, and utilization is expected to expand.

Implementation steps and selection points (excluding price information)

When introducing RTK receivers to a site, keep in mind the following steps for smooth utilization and points to consider when selecting models and services.

• Clarify implementation objectives: First, organize what you want to improve with an RTK receiver. Different objectives—streamlining earthwork volume calculation, improving as-built measurement accuracy, machine guidance, or stake setting—require different functions and accuracies. Clarifying objectives helps determine the required positioning precision (e.g., horizontal position ±2 cm, elevation ±5 cm) and the equipment configuration (standalone rover or base station+rover set).

• Check the operating environment: Next, confirm the site environment. If mobile communication is available, network RTK (Ntrip services) is convenient. In mountainous or underground areas with poor communication, you may need to set up your own base station or choose a device compatible with Michibiki CLAS signals. Consider the size of the work area and presence of obstacles; GNSS reception can be unstable in urban high-rise areas or forests, so using other surveying instruments in combination may be necessary.

• Select equipment: Compare RTK receivers that match your objectives and environment. Key considerations are positioning accuracy and reliability (multi-GNSS support, dual-frequency support, tilt compensation), operability (smartphone compatibility, Japanese support, intuitive UI), robustness (waterproof/dustproof ratings, shock resistance), and battery life (can it last a full workday). In actual field use, features such as rain operability, thermal design to avoid overheating in direct sun, and verified cold-weather performance are important. While price ranges vary, choose a model that fits your operations rather than focusing solely on cost.

• Training and trial: After purchasing or renting equipment, conduct internal training and trials before full deployment. Use manufacturer or dealer training sessions and online manuals to learn basic operations: start/stop positioning, data saving, and coordinate system settings. Initially test in company premises or safe locations, verify errors against known points, and understand device performance. Trial runs on small sites help identify data flows and precautions.

• Incorporate into workflow: Integrate RTK-acquired data into your workflow. For earthwork volume calculations, define procedures for importing data into point cloud or volume calculation software. For as-built management, map RTK outputs to existing record formats (e.g., copy coordinates into designated spreadsheets to automatically compute elevation differences). Ensure data backup and set up cloud storage or internal servers for sharing.

• Start operations and follow-up: Once RTK receivers are deployed on site, perform regular follow-up. For a while, compare positioning results with conventional methods to confirm sufficient accuracy. Continuously seek efficiency improvements by gathering feedback from field staff. If you can demonstrate internal success metrics after adoption (e.g., percent reduction in schedule, labor cost savings), these will support broader rollout or additional investment.

These are the basic implementation steps; when in doubt during selection, request hands-on demos or collect other companies’ examples. Opportunities to try RTK equipment at construction DX exhibitions and seminars are increasingly available and useful.

Practical workflow for obtaining point cloud control points via smartphone surveying using LRTK

Here we present a specific workflow for obtaining point cloud control points using the smartphone RTK receiver “LRTK.” LRTK is a smartphone-integrated RTK system; by attaching a dedicated receiver to a smartphone, anyone can achieve centimeter-level positioning. Using LRTK, control point surveying for drone-acquired point clouds can be conducted with just a smartphone, quickly producing high-precision point cloud data.

STEP 1: Prepare for the site Prepare the LRTK receiver and a smartphone or tablet with the LRTK-compatible app installed. Upon arrival, dock the smartphone and receiver and power on. LRTK runs on a built-in battery, so complicated wiring is unnecessary.

STEP 2: Connect to correction information Configure RTK positioning in the smartphone app. If communication conditions are good, set Ntrip account information in the app to receive correction data. If the site is in a mountainous area with poor connectivity, switch the LRTK to the Michibiki CLAS mode to receive augmentation signals from the satellite. The app displays the current positioning mode (float or fixed), and when it shows “Fix” within tens of seconds, centimeter-level positioning has begun.

STEP 3: Measure control points Measure control points that serve as references for point cloud data. Pre-place markers (artificial targets) on the ground, set the LRTK receiver on them, and record positions. Tapping “Start Positioning” in the app records latitude, longitude, and elevation at that moment. To increase accuracy, use the app’s averaging function to average data over 5–10 seconds to determine the coordinate value. Save point names and notes for each control point to facilitate later data processing.

STEP 4: Save and share data Measured control point data are saved on the smartphone and can also be uploaded to the cloud with a single button press. Using the LRTK cloud service allows office PCs to check coordinates measured on site immediately. After measuring all control points, review the data in the app and recheck locations on a map if needed—for example, confirming you did not record the wrong point or ensuring the number of recorded points matches the number placed.

STEP 5: Use in point cloud processing Import the acquired control point coordinates into the point cloud processing software for drone photogrammetry. Specifically, designate these control points as GCPs (Ground Control Points) when analyzing aerial images to align the model coordinates. Coordinates obtained with LRTK are already converted into high-precision geodetic or plane rectangular coordinates, so they match without offsets in the software. This results in a point cloud tied to accurate coordinate systems such as those of the Geospatial Information Authority, producing high-quality 3D models ready for as-built management and quantity calculations.

This is the workflow for control point surveying using LRTK. Tasks that formerly required a GNSS receiver plus controller can now be completed with just a smartphone, eliminating transcription errors and reducing effort. Even technicians with limited surveying experience can operate intuitively, significantly reducing on-site burden and speeding up work.

Use cases on site (stake setting, photogrammetry, AR navigation, volume calculation)

The introduction of RTK receivers has created new applications across various on-site scenarios. Below are major use cases and how they can improve efficiency and sophistication.

• Stake setting and layout work: Stake setting (position marking) and layout marking for structures require accurate coordinates. RTK receivers allow design coordinates to be reproduced on site. Practically, operators move while viewing the difference between current and target coordinates on the smartphone screen and place stakes or paint markings when the positions match. Traditionally, a surveyor used a total station and one person guided with a prism, but RTK enables a single person to set multiple points quickly. RTK is especially effective on open development sites and long road alignments, reducing stake errors and rework.

• Photogrammetry (drone and ground photography): High-precision positional information attached to images is important for drone photogrammetry and ground photography. RTK can be used in two ways: either integrated with RTK-equipped drones or cameras to record corrected coordinates at the time of shooting, or by surveying multiple control points with RTK within the shooting area to correct models during image processing. Either approach dramatically improves the accuracy of resulting point cloud models, enabling reliable 3D models for volume calculation and as-built verification in a short time. Increasingly, site supervisors perform simple photogrammetry themselves using tablets and RTK, making frequent 3D point cloud acquisition a routine part of daily operations.

• AR navigation and visualization: RTK’s centimeter accuracy opens new possibilities when combined with AR (augmented reality). For example, if design positions of underground pipes or cables are available, those positions can be overlaid on the camera view of a smartphone or tablet to visualize otherwise invisible infrastructure on site. Because RTK determines the device’s position and orientation in real space with high accuracy, the mismatch between digital data and reality is minimized and AR guidance becomes practical. You can place a virtual flag at a stake point in AR and guide workers intuitively to the target. In as-built management, color-coded heat maps of differences from design can be displayed on actual structures via AR, enabling immediate visual confirmation of defects. RTK receivers provide the positional accuracy foundational to such AR-based site management.

• Volume calculation and as-built quantity management: For earthworks and land development, managing fill and excavation volumes is crucial for scheduling and cost control. RTK receivers greatly streamline volume measurement and calculation that previously took days. For example, walking around a spoil heap with an RTK-equipped smartphone to create a point cloud and then instantly calculating its volume is now possible. The resulting numbers can be checked on site, answering questions like “How many truckloads remain?” or “We’ve excavated ○○ m³ more than planned,” enabling timely adjustments to haul plans and daily quantity reporting to clients. Accumulated measurement data can also serve as 3D evidence to substantiate as-built quantities at project completion. High-precision volume calculations enabled by RTK receivers directly contribute to improving and accelerating field construction management.

Conclusion: Prospects for efficiency and high-precision management with RTK receivers

Introducing RTK receivers is a trump card for dramatically increasing productivity and improving management accuracy at construction and surveying sites. High-precision measurements that previously relied on specialized departments or outsourcing are becoming tasks that field staff can perform routinely. As a result, workflows that digitally record every as-built datum on site and reflect it in immediate decision-making are becoming reality. RTK receivers, especially the new generation that links with smartphones, are moving toward “one person, one device” ubiquity, and in the future each worker may carry their own surveying tool to fully understand every corner of the site.

This trend will transform the construction PDCA cycle. For example, reviewing previous day’s point clouds every morning and revising construction plans accordingly reduces rework and material waste. Increased surveying frequency and coverage allow early detection and on-the-spot correction of construction errors or defects, preventing quality issues from propagating. From a safety perspective, remote measurements of hazardous areas and guidance for heavy equipment operation can reduce accident risk.

As 3D data utilization expands, site “visualization” and DX are expected to accelerate further. The fusion of high-precision GNSS technologies and digital tools will update construction management with unprecedented efficiency and accuracy. Consider evaluating the benefits of introducing RTK receivers now—new prospects for balancing on-site efficiency and high-precision management are well within reach.

FAQ: Frequently asked questions about RTK receivers, positioning accuracy, point cloud data integration, etc.

Q1: What is the difference between an RTK receiver and an ordinary GPS? A1: Ordinary GPS typically has meter-level errors, whereas RTK receivers use correction information from a base station to achieve centimeter-level positioning. The major difference is that RTK cancels errors in real time, providing accurate coordinates on the spot. For example, an ordinary GPS may give slightly different positions each time you measure the same point, but RTK consistently yields nearly identical values, making it suitable for as-built management and comparison with design drawings.

Q2: Is a base station always required for RTK positioning? A2: It is not always necessary to set up a physical base station. Using network RTK services (VRS or Ntrip distribution from reference points) allows a standalone rover receiver to perform positioning. In Japan, Michibiki CLAS is another option; compatible receivers can obtain correction information without an internet connection. However, deploying your own base station can provide optimized accuracy for your construction area, so base station + rover operation is used in some large-scale sites.

Q3: How reliable is RTK positioning accuracy on construction sites? A3: Properly operated RTK typically achieves horizontal errors around 2–3 cm and elevation errors within about 5 cm. In open environments with few obstructions, even higher accuracy is possible, and static measurements averaged over time can achieve sub-centimeter accuracy in some cases. However, accuracy degrades under overpasses, tree cover, or other GNSS-disturbing environments, so supplemental use of total stations may be necessary. In general, RTK receivers provide sufficient accuracy for as-built management and volume calculations, while millimeter-level precision for structural measurements may require laser scanners or combined approaches.

Q4: How do you align point cloud data obtained with an RTK receiver to design data? A4: Using RTK provides accurate coordinates to point cloud data, so you can generally overlay them directly onto design coordinates. For example, if design data are in the public plane rectangular coordinate system, RTK-acquired point clouds will have matching values and can be compared without special transformations. If survey coordinate systems differ, you can perform georeferencing by translating and rotating the point cloud using known points. Compared to pre-RTK workflows, aligning point clouds to design data has become much easier.

Q5: Do you need special certifications or licenses to introduce RTK receivers? A5: No special license is required to operate an RTK receiver itself—anyone can use it. However, if you operate your own base station using radio equipment, a radio station license may be required depending on the wireless equipment used (many commercial RTK devices use license-exempt low-power radios or Bluetooth, so licensing is not necessary). Using network RTK services requires a contract with a provider. Manufacturers and dealers offer training, so take advantage of those opportunities when introducing equipment for the first time.

Q6: Can a smartphone’s GNSS achieve RTK-like high-precision positioning? A6: Recent smartphones include high-performance GNSS chips, and some can obtain raw observation data for RTK processing. However, smartphone antennas are small with limited reception sensitivity, so achieving stable centimeter-level accuracy solely with a phone is currently difficult. Connecting a dedicated RTK receiver (antenna) to the smartphone captures satellite signals robustly and enables high-precision positioning. Thus, the combination of a smartphone plus an external RTK receiver best balances convenience and accuracy. Smartphone-integrated devices like LRTK maintain smartphone usability while providing survey-grade accuracy, and their use is spreading across many sites.