Pile-Driving Coordinate Guidance Made This Easy! Improve Construction Accuracy with LRTK CLAS-Compatible Receivers

Table of Contents

• What is CLAS? Differences from RTK and benefits

• Required accuracy for pile-driving and traditional challenges (TS, tape measures, limits of optical instruments)

• Basic configuration and workflow of coordinate guidance using CLAS-compatible receivers

• Pile-driving coordinate guidance steps with LRTK (equipment setup, selecting points, AR guidance)

• Using public coordinates vs. local coordinates, and cautions

• Site case studies and results (accuracy, time savings, reduced manpower, etc.)

• Site management integrating point clouds and photogrammetry (pile position verification, as-built control)

• Natural introduction of smartphone surveying with LRTK (on-site and cloud use)

• FAQ: questions about CLAS, LRTK, and coordinate guidance

What is CLAS? Differences from RTK and benefits

First, CLAS is the “centimeter-class positioning augmentation service” provided by Japan’s Quasi-Zenith Satellite System (QZSS, “Michibiki”). It creates correction data based on error information from the Geospatial Information Authority of Japan’s continuous reference station network and transmits this directly via satellite, improving GNSS positioning accuracy to within a few centimeters. With a dedicated CLAS-compatible receiver, correction data can be received via satellite without a communication line or a local base station, enabling high-precision positioning anywhere in Japan. A major appeal of CLAS is that this correction signal is free, and the service is reliable even in mountainous areas outside mobile coverage or at disaster sites.

On the other hand, conventional RTK positioning (Real Time Kinematic) uses a pair of GNSS receivers—a base and a rover—and computes position by applying the real-time difference between the satellite signals received at both. Traditionally, this required setting up your own base station on site or receiving base station data over a communication network (VRS, etc.). In other words, high-precision positioning required radios, internet connections, and sometimes paid correction services. The main difference between CLAS and RTK is how correction information is obtained. CLAS-compatible equipment receives corrections directly from satellites, so it can operate standalone without distance limitations to a base station. RTK accuracy is more stable closer to the base station, whereas CLAS provides near-uniform accuracy nationwide. Also, because CLAS does not rely on communications infrastructure, it can be used where network connectivity is difficult and remains effective at disaster scenes where communications are down. Overall, CLAS can be described as a “wide-area, easy RTK” that provides centimeter-class accuracy while significantly reducing costly equipment and complex preparation.

Required accuracy for pile-driving and traditional challenges (TS, tape measures, limits of optical instruments)

Pile-driving tasks on civil and construction sites (such as installing survey stakes or locating foundation piles) are critical processes that affect the quality of the entire structure. If piles are not placed at the exact coordinate positions specified in the design drawings, subsequent work may be misaligned, leading to defects or construction errors. Therefore, pile-driving requires high accuracy where even errors of a few centimeters are unacceptable. However, traditional pile location layout has relied heavily on manual surveyor work.

Traditionally, surveyors used drawings to determine coordinates on site and marked locations on the ground with tape measures or total stations (TS), then marked stakes or spray paint. This approach has several challenges. First, it is time-consuming and labor-intensive. Crews often worked in pairs to set batter boards, re-measured repeatedly, and required careful preparation. There is also a high potential for human error—mistakes in identifying survey points or in marking can force rework. Optical TS surveys require line-of-sight, making work difficult in complex terrain or where obstacles exist. For example, in mountainous areas or in conditions with poor visibility such as at night or in fog, the limitations of visual guidance make it hard to ensure accuracy. Many projects also depend on specialized survey teams, resulting in high personnel costs and workflows affected by weather and time of day. In short, traditional pile-layout surveying demanded tremendous effort to achieve accuracy and was inefficient.

Basic configuration and workflow of coordinate guidance using CLAS-compatible receivers

A solution to these issues is GNSS coordinate guidance for pile-driving. By combining a CLAS-compatible high-precision GNSS receiver (for example, the LRTK series) with a smartphone, anyone can easily be guided to the target coordinates for pile installation. The basic configuration is a compact CLAS-capable RTK GNSS receiver and a smartphone or tablet with a dedicated app installed. The receiver collects multiple satellite signals including augmentation signals in the millimeter-wave band (L6 band) and computes a high-precision current position. The receiver pairs with the smartphone via Bluetooth or cable, sending real-time positioning data (current coordinates) to the app.

On site, power on the receiver and acquire satellites in an open sky. If CLAS satellite augmentation is available, centimeter-class positioning becomes possible within a few minutes. Next, load the design coordinate data for the project into the smartphone and select the pile positions (survey points) you want to guide to in the app. The app displays your “current position” and the “target pile position,” and updates the direction arrow and distance in real time. The worker follows the guidance on the smartphone and moves until the receiver they carry matches the target coordinates. By using the smartphone’s camera, an AR display can overlay a marker for the target point on the live camera view, making it intuitive to identify “this is where the pile should be driven.”

The workflow for coordinate guidance is simply “high-precision measurement of current position” → “comparison with target coordinates” → “movement guided by the app.” What used to be a manual transfer of coordinates from drawings to the field becomes a digital, automated process via the GNSS receiver and app. This enables less experienced workers to place piles accurately without pre-marking by a surveyor. CLAS-compatible receivers make coordinate guidance usable immediately on site by simply preparing the equipment and selecting point data, so the basic setup is accessible even to those without surveying expertise.

Pile-driving coordinate guidance steps with LRTK (equipment setup, selecting points, AR guidance)

Now, let’s look step-by-step at how to perform pile-driving coordinate guidance using an LRTK device and a smartphone.

• Equipment preparation and setup: Upon arrival at the site, attach the LRTK receiver to its mount (for example, the top of a dedicated pole or above the smartphone). Power on the receiver and establish a Bluetooth connection with the smartphone or tablet. Launch the LRTK app and confirm that GNSS positioning data is being received from the receiver (check satellite fix status and accuracy indicators and ensure a Fix solution is obtained).

• Loading and selecting survey point data: Import the design coordinate data prepared in advance into the app. This is typically a list of pile coordinates from construction drawings, loaded as a CSV or similar format. Select the pile point number you want to guide to from the list to set that coordinate as the target. Confirm site coordinate system settings if necessary (public coordinate zone or local coordinate offsets).

• AR-guided alignment: After selecting a point, the screen shows the “bearing to target” and “distance,” so hold the smartphone and move in the indicated direction. While moving, the app’s arrow and distance readout update in real time, decreasing as you approach the target. Turning on AR mode projects markers or flags representing the target point onto the camera view—appearing, for example, like a red pin on the ground—so you can visually identify the pile location. Because GNSS tracks your position with high precision, the AR marker aligns with the actual location and remains stable as you move.

• Marking and installing the pile: When the displayed distance is nearly zero and the AR marker appears at your feet, that is the design coordinate pile location. Confirm there is no offset, mark the ground (place the pile temporarily or spray paint), and install the pile with machinery or a hammer. If the receiver remains attached during installation, you can measure the pile head coordinates immediately after driving to verify no displacement occurred.

• Recording and moving to the next point: After installing the pile, mark the survey point as complete in the app. If necessary, measure and save the coordinates of the installed pile and take photos for records. These data can be uploaded to the cloud automatically, enabling immediate sharing without returning to the office. After finishing one pile, select the next point and repeat the steps. Repeating this flow allows a single person to complete sequential pile-driving tasks—one of the major advantages of LRTK-based coordinate guidance.

*(※Fix解: This refers to a GNSS solution with centimeter-level errors. Single-point positioning or Float solutions (with accuracy on the order of tens of centimeters) are not sufficient for pile-guidance, so you must wait until a Fix solution is obtained.)*

Using public coordinates vs. local coordinates, and cautions

When using GNSS it is important to be mindful of the site’s coordinate system. In Japan, surveying and design commonly use public coordinate systems (such as the plane rectangular coordinate system based on JGD2011), but some sites adopt a custom local coordinate system (with an arbitrary origin and orientation). CLAS-capable receivers generally output Earth-referenced coordinates like WGS84 or JGD2011, which may not match the coordinates on the site drawings without transformation. Therefore, a process called localization (site calibration) is needed to align coordinates.

Specifically, measure known control points on site (points with verified coordinates) with GNSS, compare those measured values to the design coordinates, and calculate the necessary translation and rotation. Apply these correction parameters in the app or receiver so all GNSS-derived points are transformed to the local coordinate system. For example, if you base alignment on public control points from the Geospatial Information Authority of Japan, you can match the public coordinate system (the relevant zone). If you use known points defined in a previous project’s local coordinate system, you can align to that local system.

A key caution is to always follow the coordinate system specified in the design documents or by the client. For sites using public coordinates, set the LRTK app to the appropriate plane rectangular coordinate zone or output latitude/longitude and convert later. For local coordinate systems, you should observe at least one known point (preferably multiple) on site and perform localization, otherwise coordinates will be offset. Pay special attention to vertical positioning as well: GNSS provides ellipsoidal height, which differs from the site TBM (benchmark) heights. Perform geoid height conversions or adjust using known site elevations as needed to manage vertical errors. Properly handling coordinate systems allows CLAS-capable GNSS positioning to be used directly in the site’s coordinate system, ensuring smooth data consistency for later phases.

Site case studies and results (accuracy, time savings, reduced manpower, etc.)

Sites that implemented high-precision LRTK coordinate guidance systems report not only improved accuracy but also significant gains in efficiency and cost savings. Below are the main effects and examples.

• Dramatic improvement in construction accuracy: GNSS guidance drastically reduces human error, enabling piles to be driven within a few centimeters of target coordinates. Even in cases where machine operators previously relied on marks set by survey teams and intuition, following terminal guidance ensures precise positioning. This reduces variation in pile locations and has enabled some teams to achieve zero rework, improving quality control. Accurate pile-driving prevents foundation misalignment and contributes to the overall quality of the structure.

• Significant time savings: Introducing GNSS coordinate guidance has dramatically shortened pile layout time in many cases. For example, in one comparison, using a GNSS + AR pile-driving system reduced work time to about one-sixth of that required by traditional optical surveying methods. Simplifying point layout procedures and improving movement efficiency greatly increases the number of piles that can be handled per day. In one road construction project, stake setting that used to take half a day was completed in under an hour, directly shortening the construction schedule. Time savings translate into reduced construction costs and more buffer in the schedule, boosting overall site productivity.

• Reduced manpower, labor savings, and improved safety: Tasks that previously required two to three people can be completed by one person using LRTK. Eliminating the need for survey assistants or checkers significantly reduces labor costs and allows reallocation of personnel to other tasks. Fewer people on site during machinery operation also lowers exposure to hazards, improving safety management. For example, on a bridge site where surveyors had to enter narrow scaffolding to mark locations, GNSS guidance replaced that risky work and allowed safe and speedy pile foundation layout. Workers report being “freed from the heavy labor of setting batter boards and tape measures” and that work in extreme weather becomes quicker, reducing physical burden. These labor savings have improved working conditions on many sites.

• Broader applicability (useful across many site types): Pile-guidance via coordinate guidance is being adopted across roadworks, bridge construction, water and sewer projects, and site development. In road projects, high-precision pile installation along the centerline and marking of property boundaries eliminated the need for traditional batter boards. In bridge works, GNSS guidance improved placement of pier locations in mountainous, low-visibility conditions. For long pipeline installations, consistent interval marking was completed efficiently by a single operator, allowing large-area surveying in a short time. Thus, accuracy and efficiency can be balanced across diverse jobs, and with the Ministry of Land, Infrastructure, Transport and Tourism promoting i-Construction (ICT-enabled construction), adoption is expanding from major contractors to small and medium-sized firms.

Site management integrating point clouds and photogrammetry (pile position verification, as-built control)

LRTK-based pile guidance offers added value through the immediate use of surveying data. Position information obtained with a GNSS receiver and smartphone can be directly associated with photos and point cloud data for site management.

For example, if you photograph a pile immediately after installation with a smartphone, the photo can be tagged with high-precision coordinates and timestamps. Plotting these photos on a cloud map later makes it easy to see “which pile was installed where.” This is powerful for pile position verification and preparing as-built documentation. Compared to paper field books, digital photos with coordinates reduce errors and are easy to share, providing convincing evidence for inspections.

Modern smartphones and tablets increasingly include simple photogrammetry or LiDAR-based 3D point-cloud scanning capabilities. Combined with LRTK, these point clouds can be assigned absolute coordinates (public coordinates) in real time. For example, scanning terrain or structures with an iPad LiDAR and fusing that data with the high-precision position and attitude information provided by LRTK yields an accurately georeferenced site point cloud. These 3D point clouds can be used directly for as-built control: after pile installation, capturing surrounding ground and structures allows digital verification of pile positions and elevations against design. You can measure distances between piles, inclinations, and relationships to nearby features on the point cloud to check deviations from design—advanced quality control that can be performed on site immediately.

Additionally, uploading point clouds and photos to cloud services enables real-time sharing with the office or subcontractors. On-site personnel can install piles while office staff prepare as-built inspections in parallel. A smartphone + LRTK workflow centered on positioning and measurement optimizes site management by seamlessly connecting “construction” and “as-built verification,” which were previously separate processes.

Natural introduction of smartphone surveying with LRTK (on-site and cloud use)

For sites new to ICT equipment, concerns about “can we use it effectively?” are common. Smartphone-linked GNSS receivers like LRTK dispel this worry with their ease of use and familiar interface. Because the platform is a smartphone people already use daily, site personnel can operate it intuitively and start without deep expertise. On LRTK adoption sites, feedback includes “surveying felt like using a smartphone app” and “newcomers didn’t get confused because aligning coordinates felt like a game.”

Starting with a concrete use case like pile guidance makes acceptance on site easier and leads to smooth expansion into broader smartphone surveying. After using LRTK for pile-driving, crews often try using the same equipment for topographic surveys or photo records of as-built conditions—the range of use naturally grows. Once accustomed to the system, teams find many applications: using the device as an electronic field book for point surveys, simple depth or height checks, installing control points for drone photogrammetry, and more—realizing that smartphone + GNSS is a versatile surveying tool for many site scenarios.

LRTK also integrates with cloud services (LRTK Cloud), allowing immediate upload of survey data, photos, and point clouds from the field. Teams can share data, view maps in a browser, and streamline data management and reporting. The tedious process of returning with a USB drive and importing into a PC is replaced by unified real-time cloud management. This lowers the barrier to “site DX,” shifting management away from paper and manual tasks to digital workflows.

The effects of introducing smartphone surveying with LRTK go beyond single-task efficiency gains. LRTK serves as a catalyst for site-wide digitalization and labor savings, contributing to productivity improvements and work-style reform. Even a small initial success—“we could do pile-driving with a smartphone”—builds confidence and interest, leading next to “we can do surveying with a smartphone” or “we can visualize the site with the cloud.” Because of its low barrier to entry, LRTK is truly a key tool that naturally drives DX on the jobsite.

FAQ: questions about CLAS, LRTK, and coordinate guidance

Q: What do I need to use CLAS? How does it differ from traditional RTK? A: To use CLAS you need a CLAS-compatible GNSS receiver (such as LRTK) and an environment where satellite signals can be received. Internet or base stations are not required; a dedicated receiver can receive correction signals directly from satellites. Traditional RTK required base station data, whereas CLAS enables standalone centimeter-class positioning across the country—this is the main difference.

Q: How accurate is the LRTK receiver? Is it reliable? A: High-precision GNSS receivers like LRTK achieve planar positions within a few centimeters, and vertical errors on the order of a few centimeters to several tens of centimeters (under good conditions, horizontal accuracy is about 2–3 cm (0.8–1.2 in)). When a CLAS or RTK Fix solution is obtained, positioning is very stable and sufficient for pile-driving and as-built measurements in civil works. Note that accuracy may temporarily degrade where satellite signals are obstructed, so maintaining a clear sky view is desirable. Regular checks against known points help ensure reliability.

Q: Can someone new to GNSS guidance use it? Is expert knowledge required? A: Yes. Smartphone apps are designed to be intuitive so people without surveying experience can use them. You just follow the arrows and distance shown on the app, so beginners rarely get lost. A short introduction or training session is usually enough for both young and experienced workers to operate the system. The system automates complex coordinate calculations and settings, so those unfamiliar with surveying can start with confidence.

Q: How do I use a local coordinate system? A: The LRTK app supports public coordinate systems (plane rectangular coordinate zones) and WGS84 latitude/longitude. If your site uses a custom local coordinate system, observe at least one known point (with known local coordinates) on site and use the app’s localization feature to apply corrections. Typically you input the difference between the measured and theoretical values for the known point to correct subsequent positioning. The procedure is simple and documented in the manual; it usually only requires entering a few numbers in the app.

Q: Is CLAS satellite augmentation available outside Japan? A: CLAS targets Japan and its surrounding regions and is available almost nationwide within Japan, but it is not available overseas. For high-precision positioning abroad, use local satellite augmentation services (SBAS or other PPP services) or internet-based RTK services. The LRTK receiver supports multi-frequency multi-GNSS and can perform RTK abroad if connected to an NTRIP service.

Q: Can it be used in harsh environments like rain or cold regions? A: LRTK receivers have dustproof and waterproof performance and can operate in light rain (many models are rated around IP65–IP67). Operating temperature ranges are wide, and they have been used from snowy mountains in winter to extreme heat in summer. Batteries have been tested for cold environments and reports indicate operation around -20℃. However, as electronic devices, take precautions when exposed to heavy rain for extended periods. Harsh environments can also degrade satellite reception, so operate with attention to weather conditions.

Q: Beyond pile-driving, what other applications are there? A: LRTK is useful for many positioning and surveying tasks beyond pile guidance: elevation surveys for pavement and as-built checks, recording locations of buried utilities, placing ground control for drone photogrammetry, machine guidance for earthworks, point surveys for as-built drawings, and even agricultural field parcel surveys or tree-planting location guidance in forestry. The convenience of obtaining high-precision positions with a smartphone has increased cases where teams handle surveying themselves instead of outsourcing. In short, any task that requires setting out positions or measuring can potentially use LRTK.