Dramatically Improving Surveying Accuracy and Efficiency: Latest Technologies and On-site Know-how

Surveying tasks performed at structural foundation construction sites (such as laying out reference lines and marking pile centers) are crucial processes that determine the overall quality and progress of the work. Because even a slight deviation can cause rework in later stages or defects in the structure, millimeter-level precision is required. However, conventional surveying tends to require experienced personnel and considerable labor, so improving efficiency has been a long-standing issue. This article explains the latest surveying technologies and on-site know-how that dramatically improve accuracy and efficiency in surveying. We focus especially on mobile surveying technology that combines smartphones with GNSS (RTK), and compare its labor-saving, responsiveness, and accuracy-maintaining advantages with traditional total station–centric workflows. We also touch on integration with ICT construction machinery, cloud-based data sharing, and points to watch during implementation, offering practical tips for bringing the latest technologies to the field. At the end of the article, we present a case study using a smartphone RTK system (simple RTK LRTK) in foundation work, encouraging readers to adopt this new approach naturally as a way to reduce on-site burdens while ensuring accuracy.

Importance of surveying tasks and current challenges

In foundation construction for buildings, surveying is an indispensable step. Accurately transferring positions and elevations from design drawings to the actual site ensures the correct placement of structural elements. Surveying work includes tasks such as installing pile centers (pile center points) for buildings or piers with no centimeter-level deviation, accurately marking the construction reference lines that outline a building, and precisely setting foundation elevation levels. These tasks have a direct impact on construction quality and therefore require high precision, and are normally carried out with great care by specialized surveyors.

However, there are several challenges in current surveying practices. First, the labor and personnel burden is large. To ensure accuracy, meticulous measurements and multiple confirmations are needed, and it is not uncommon for experienced technicians to work in teams. Second, there is poor responsiveness. When design changes or site conditions require “re-establishing a reference line here” or “adding pile centers,” traditional surveying methods make immediate response difficult, often causing time lags due to scheduling external survey crews and preparing equipment. Third, data recording and management tend to be analog-centered. Recording dimensions and angles by hand on site and later transferring them to drawings in the office introduces risks of mistakes and time loss. Methods that allow a small team to survey quickly and accurately have therefore been sought.

Traditional total station surveying and inefficiencies

A widely used conventional surveying method is using a total station (TS). A total station is a precision instrument that optically measures angles and distances; a pole with a prism is held by another worker and targeted to define the position of the target point. In foundation work, a TS is typically set up on pre-established control points (points with known coordinates), and backward intersection is used to set the position and orientation, guiding pile drivers to the coordinates from the design drawings. For example, when marking a pile center, the TS operator gives angle and distance instructions while an assistant marks the pile position. When laying out reference lines, TS measurements are used at both end points and string lines or chalk are used to indicate the line by connecting them.

While total stations enable high-precision surveying, there are several inefficiencies. First, at least two or more people are required, creating a personnel scheduling burden. One person operates the TS while another carries the prism and moves to the target point, so multiple workers are always tied up. Especially for wide-area surveys, cooperative communication slows the work. Next, setup time for equipment is required. The TS must be mounted on a tripod and precisely leveled, and each time it is set up it must be aligned with control points or adjusted against two known points (angle correction). As measurement points increase, re-setting and re-aiming for back-sighting occur, reducing efficiency. There are also line-of-sight constraints. TS surveying requires a direct line of sight from the instrument to each prism target. If obstacles (material piles, heavy machinery, temporary structures, etc.) block the view, measurements cannot be made, so workers must move to positions where measurement is possible or divide measurements and calculate relative positions, increasing labor. In terms of data management, field measurements are often only marked on stakes or the ground, with electronic records limited to the TS unit or handwritten notes. This makes it cumbersome to verify measured coordinates later or reuse them with other equipment. Overall, TS surveying is reliable in terms of accuracy, but it is labor- and time-intensive and lacks flexibility in some situations.

Mobile surveying with smartphone + GNSS (RTK)

To address these issues, the recently introduced smartphone + GNSS (RTK) mobile surveying technology has attracted significant attention. By combining a smartphone with GNSS, you can easily achieve centimeter-level positioning accuracy and streamline surveying tasks. RTK (Real Time Kinematic) is a technique in which a base station at a known point and a rover both perform satellite positioning simultaneously; the base station transmits correction information to the rover to correct its position in real time. As a result, typical GPS standalone errors of several meters can be reduced to a few centimeters. Previously, expensive, dedicated GNSS surveying equipment and radio devices were required, but today RTK positioning is possible with a commercial smartphone paired with a small GNSS receiver.

Smartphone RTK positioning is notable for its mobility and ease of use. Smartphones are everyday tools that everyone carries; by attaching a GNSS receiver, high-precision surveying can be conducted anywhere, anytime. Heavy tripods and mounting are unnecessary: turn on the device, launch the app, and positioning starts immediately. Positioning results are shown on the phone screen as numerical values and guides, designed to be intuitively understood even without specialized surveying knowledge. For example, the app can display “0.05 m east and 0.02 m north from the current location” in real time, so the user only needs to move until the display shows near zero. Smartphones also have communication capabilities and can receive base station correction data via the internet, supporting network RTK. This means that without installing a dedicated base station on site, correction data can be obtained from sources such as the Geospatial Information Authority of Japan’s (GSI) Continuously Operating Reference Stations (VRS method). Japan’s QZSS “Michibiki” provides a centimeter-level augmentation service (CLAS), and compatible receivers can obtain high-accuracy corrections via satellite even outside internet coverage. With these mechanisms, smartphone RTK’s ability to deliver centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)) while being portable by one person and enabling instant high-precision positioning is revolutionary and has the potential to significantly change surveying workflows.

How the simple RTK system “LRTK” works and its benefits

So what do you actually need to use smartphone RTK on site? A representative example is the simple RTK system “LRTK”. LRTK is an integrated solution developed by a startup originating from Tokyo Institute of Technology, combining a compact RTK-GNSS receiver with a smartphone app and cloud service. By attaching a dedicated ultra-compact GNSS receiver to a personal iPhone or iPad, the smartphone itself becomes a centimeter-precision surveying instrument. The receiver weighs about 125 g and is thin—just over 1 cm (0.4 in)—roughly the size of a phone case, and can be carried in a pocket. It runs on an internal battery and connects wirelessly to the smartphone. The equipment is simple: a dedicated phone case and a snap-on receiver. An optional monopod (pole) is available to stabilize the phone for more stable positioning when needed.

An example of the compact GNSS receiver “LRTK” integrated with a smartphone. By mounting it on the back of an iPhone, centimeter-level positioning becomes possible. Launch the dedicated app and a single person can perform high-precision surveying while collected data is immediately shared to the cloud.

One major benefit of LRTK is that its positioning accuracy rivals existing high-end surveying instruments. For single-point real-time positioning, horizontal errors are about 1–2 cm (0.4–0.8 in) and vertical errors are about 3 cm (1.2 in). Moreover, by using the app’s averaging function to take multiple measurements, errors can be reduced to the millimeter range. This approaches the accuracy of total stations for pile positioning and is sufficient for on-site surveying needs. The ease of operation is also notable: the smartphone screen clearly shows the current reception status (number of satellites tracked and whether correction data is applied), and whether an RTK “FIX” (integer solution) has been achieved can be checked at a glance. If satellite reception worsens and accuracy degrades, the app displays a warning for safety.

LRTK is not just a positioning device but is designed as an integrated tool supporting a wide range of field tasks. The dedicated app includes 11 functions such as recording survey points (coordinates), continuous measurement for terrain scanning, checking against design data, photo capture and memo storage, and AR (augmented reality) overlays of virtual models. For example, using the iPhone’s built-in LiDAR scanner, you can capture point cloud data of a location and immediately generate a 3D model. Captured point clouds and survey data can be stored offline on the phone and uploaded to LRTK Cloud with one tap when online. On the cloud, surveyed point coordinates, photos, and point cloud models can be reviewed on 2D/3D maps, with tools for distance/angle measurement, cross-section extraction, and volume calculation. This greatly reduces the tedious task of bringing field data back to the office for drawing work. Sharing data via the cloud lets stakeholders grasp progress and survey results in real time without being physically present. In this way, LRTK is engineered to let a single smartphone complete the entire sequence of surveying tasks, and its reasonable price point encourages adoption as a “one-per-person” site tool.

A single-user surveying scenario using LRTK. The phone and receiver are mounted on an optional monopod (pole), and the worker measures pile positions. The app allows height offset corrections and shows positioning status on screen, enabling accurate marking. Tasks that traditionally required two people, such as marking pile centers, can be performed quickly by one person as shown.

Marking pile centers and laying out reference lines with smartphone RTK

Using smartphone RTK (e.g., LRTK) dramatically streamlines traditionally labor-intensive tasks such as marking pile centers and laying out reference lines. Let’s look at specific procedures and benefits.

First, applying it to pile center marking in pile-driving work. Typically, design drawings provide the center coordinates for each pile. Traditionally, these were computed from control points using offsets and marked on site with tape measures or TS. With smartphone RTK, you pre-load pile coordinate data into the app or read it via the cloud. The worker walks to an approximate pile location holding the phone and fine-tunes while following the app’s display showing distance and direction to the target coordinate. For example, the app may show “0.05 m east, 0.02 m north” (0.05 m (0.16 ft), 0.02 m (0.07 ft)), and the worker simply moves until the display is near zero. Once at the target, the worker marks the pile center with a screw or spray marking. This simple procedure allows anyone to easily set pile centers. There are tips for accuracy—holding the phone as vertical as possible and waiting a few seconds for stable reception—but even so, it’s far faster than setting up a TS and coordinating with a survey team. The larger the number of piles, the greater the efficiency gain: for example, what used to take 2–3 people half a day for 50 pile centers can in practice be done by one person in a few hours with smartphone RTK.

Next, applying it to laying out construction reference lines. A reference line is the baseline used to place buildings and structures on site, corresponding to an axis in a plane rectangular coordinate system. Traditionally, TS was used to determine end points of the reference line, and a string was stretched between them to indicate a straight line. With smartphone RTK, placing multiple points along a straight line is easy. For example, register the start and end coordinates of the reference line in the app and measure them sequentially on site. Mark the start and end points, and connect them to form the reference line. Alternatively, predefine several intermediate points at suitable intervals along the line and measure them in order. GNSS positioning gives each point independently, so theoretically slight deviations may occur when connecting points, but with high-precision RTK these errors are typically below a few centimeters and are acceptable as construction reference lines. If a perfectly precise straight line is essential, you can run a string along the measured points and adjust, but at least the coordinate acquisition part is instantaneous, offering a huge efficiency advantage. Smartphone RTK is not constrained by ground-level line of sight, so even on sites with scattered obstacles you can measure each required point individually, effectively ensuring “line of sight” via satellite even when the ground line is not visible.

Thus, smartphone RTK enables dramatic labor savings for pile center and reference line surveying. Tasks that once relied on the judgement and skill of experienced surveyors can now be performed by following digital guidance, reducing human error and preventing rework. In practice, many sites adopt a hybrid approach: critical points are double-checked with TS or levels as before, while numerous other points are quickly handled by smartphone RTK. This is far more efficient than doing everything the traditional way while still maintaining accuracy.

Comparing accuracy and efficiency with total station surveying

Here we compare the traditional total station method and smartphone RTK surveying in terms of accuracy and efficiency.

• Personnel: Total station surveying typically required teams of two (sometimes three). Conversely, smartphone RTK surveying is fundamentally a one-person operation. There is no need to coordinate multiple people’s schedules, making surveying feasible even at small crew sites.

• Setup time: TS required setup, back-sighting, and test measurements each time, while smartphone RTK requires only a few tens of seconds from power-on to position fix. No complex instrument adjustments are needed, so you can start surveying whenever needed.

• Survey speed: TS involves a cycle of aiming, reading, and instructing for each point. Smartphone RTK allows the worker to move continuously while surveying. For multiple pile points, movement losses are minimal, and using continuous measurement features you can collect points every few seconds, enabling substantial time savings.

• Line-of-sight constraints: TS requires a visible path from the instrument to the target, but smartphone RTK needs only visibility to satellites overhead. Even in sites with ground-level obstacles like material stacks or temporary fences, you can approach and measure each point. However, be mindful that RTK requires sufficient sky visibility; in narrow sites surrounded by tall buildings, inside tunnels, or indoors satellites may not be available and RTK will not function—TS or conventional methods are still needed in such cases. In short, this technology performs best outdoors with an open sky.

• Survey accuracy: TS used by skilled operators can achieve millimeter-level horizontal and vertical accuracy. Smartphone RTK, as noted earlier, typically achieves horizontal ±1–2 cm (±0.4–0.8 in) and vertical ±3 cm (±1.2 in). Although TS may appear superior, in many foundation work scenarios this level of error is practically acceptable (pile position tolerances are generally on the order of ±a few centimeters). Moreover, smartphone RTK reduces human errors—such as mistakes in tape measurements or calculation errors—so practical reliability of accuracy can be high. The important point is that both methods can ensure sufficient accuracy when used correctly.

• Data utilization: TS surveying required dedicated data recorders or manual input to use coordinate data. Smartphone RTK acquires and stores digital coordinate data simultaneously. You can upload measured data to the cloud on the spot for cross-checking with drawings or for as-built verification. This eliminates the need to later transcribe field notebooks into CAD, reducing omissions and transcription errors.

• Equipment cost: Total stations and Class 1 GNSS instruments cost several million yen, limiting the number of units and causing wait times on site. Smartphone RTK has relatively lower initial cost; if you already have smartphones, adding small receivers is sufficient, so deploying multiple units is easier. As a result, it is realistic for many roles—from machine operators to survey staff—to have one unit each, enabling immediate use when needed.

As shown, smartphone RTK surveying has advantages across many aspects compared to traditional methods. Nevertheless, it is important to choose the right tool for the job. For example, for extremely precise vertical layout (where millimeter precision is required) use laser levels or optical instruments for final verification; for indoor piping layout, TS or simple measuring tools may be preferable. Still, many common foundation surveying tasks can be adequately accomplished with smartphone RTK, and experience shows it greatly improves overall site efficiency.

Site benefits from labor reduction, responsiveness, and maintained accuracy

The benefits of smartphone RTK introduction can be summarized in three keywords: “labor reduction”, “responsiveness”, and “accuracy maintenance”.

• Labor reduction: As noted, tasks that previously required 2–3 people can be completed by one person, freeing up personnel. Even on sites where surveyors juggle multiple duties, supervisors can quickly perform surveys during spare time, eliminating delays caused by waiting for personnel. Outsourced surveying frequency can be reduced, lowering costs. Labor reduction is not just cutting heads—it means making limited human resources more effective.

• Responsiveness: Smartphone RTK can be taken out and used immediately, enabling rapid responses to site changes. For sudden design changes, you can input new coordinates from drawings and mark them on site instantly. It is powerful in situations requiring “measure right now,” such as final checks before inspection or restoring lost control points during construction. Site supervisors can quickly perform surveys between site visits, increasing overall agility.

• Accuracy maintenance: Efficiency gains are meaningless if accuracy degrades; smartphone RTK maintains accuracy through RTK centimeter-level positioning. Digital guidance reduces human error, stabilizing as-built quality. For example, early prevention of pile center or level errors reduces rework in later stages. The ability to improve efficiency while ensuring quality is the greatest advantage of adopting this technology.

These benefits lead to dramatic productivity gains and enhanced confidence in quality control on-site. In an industry facing labor reform pressures, smartphone RTK surveying is a timely solution for achieving efficient, high-quality construction with fewer personnel.

Improving construction efficiency through integration with ICT construction machinery and data sharing

Smartphone RTK surveying is not limited to standalone measurement tasks; combined with the growing use of ICT construction machinery and cloud systems, it delivers even greater impact. Under the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, information-based construction using 3D design data and GNSS-equipped machinery (machine guidance / machine control) is expanding. If excavators or bulldozers on site are equipped with GNSS receivers and linked to design data, operators can follow monitor guidance from the cab to perform excavation and embankment tasks. This can eliminate the need for conventional batter boards (string reference frames), improving both efficiency and accuracy.

Smartphone RTK surveying supports this digital construction workflow. For example, if you survey existing terrain with smartphone RTK beforehand and capture point cloud data, you can overlay it with 3D design data to calculate cut-and-fill volumes and simulate finished accuracy. During construction, reference points and lines measured with smartphone RTK can be imported into machine systems so the entire site operates on a unified coordinate system. If coordinate data from surveying is shared via the cloud with machine operators and other teams, everyone has a common understanding of “what is where and when.” For example, when foundation excavation positions are marked with smartphone RTK and shared to the cloud, a backhoe operator can confirm them on a tablet.

It also aids quality control after construction. Measuring key points of a finished foundation with smartphone RTK and uploading them to the cloud allows the office to immediately compare them with design values. Using point cloud scanning to capture a complete 3D model of the foundation can contribute to as-built documentation. These data are useful for digital deliverables. During supervision and inspection, comparing a 3D model on a tablet makes it easier to share details that might be overlooked on paper. Survey data stored in the cloud also becomes an asset for future maintenance or expansion work.

In short, accurate positional information derived from smartphone RTK becomes the data foundation of the site, and when combined with ICT construction machinery and other digital tools, contributes to efficiency across the construction process. Extending point data into lines and areas and using it in real time among stakeholders enables smooth construction management with less waste and waiting time.

Points and precautions for on-site introduction

While smartphone RTK is innovative, several points to watch are necessary for smooth on-site introduction and effective use. Here are key tips for handling control points, verifying accuracy, and responding to inspections.

• Control points and coordinate system settings: Even when using smartphone RTK, securing control points (points with known coordinates) remains essential. If using network RTK, positioning is performed in a public geodetic system (world geodetic system) based on GSI reference stations. Confirm there is no mismatch with the coordinate system used in the design drawings. For works designed in Japan’s public surveying coordinates (e.g., JGD2011 / plane rectangular coordinate system), set the smartphone RTK output to the corresponding system to use results directly. For sites using a local arbitrary coordinate system, care is needed: if a local origin and orientation were set, you must transform world geodetic coordinates obtained by smartphone RTK into the local system. Practically, measure several known points on site with smartphone RTK and compute average translation and rotation corrections to remove offsets. Fortunately, many apps including LRTK have coordinate transformation functions, allowing you to input known point coordinates and automatically display corrected local coordinates. If establishing your own base station, always calibrate it against nearby public reference points (CORS or triangulation points). Control points are the lifeline of the project, so treat them carefully and perform periodic verification surveys even after adopting smartphone RTK.

• Accuracy verification and field checks: When introducing new equipment, make a habit of verifying accuracy internally. For example, compare points measured by smartphone RTK with points measured by conventional methods, or measure the actual distance between two known points to check errors. Initially, use traditional batter boards and levels for critical reference lines and heights while comparing results. Although differences are usually negligible, discovering a systematic discrepancy early can reveal coordinate system setup errors. Also monitor satellite reception during on-site use: being in the shadow of a building reduces satellite count and degrades accuracy, so raising the receiver higher or waiting in a clear area can help. Apps like LRTK show satellite geometry (GDOP), so identify when accuracy stabilizes. The motto is: “don’t let speed compromise caution.” Ultimately, do not blindly trust machine output—double-check with human judgement.

• Inspection response and ensuring trustworthiness: Consider how to respond to client or inspector checks. ICT construction is increasingly required in public works, and submitting point clouds or coordinates obtained by smartphone RTK as inspection materials is becoming more common. However, some regions or inspectors may still require traditional in-person verification. In such cases, explain that smartphone RTK was used and, if necessary, re-measure critical points with a total station. Even if RTK-GNSS is theoretically accurate enough, earning trust in practical operations is important. Keep measurement logs and records, such as “This pile was set using smartphone RTK on [date], and was verified by TS on [date], with error within [x mm],” to build credibility. LRTK Cloud’s archived point data and photos are excellent evidence; prepare to print or submit them when requested. Gradually, inspectors are becoming accustomed to digital as-built verification. To avoid questions like “Is the accuracy OK?”, maintain rigorous quality control of deliverables and steadily increase confidence in new technologies.

Case study: effects of smartphone RTK surveying

Finally, here is a real-world case study of smartphone RTK introduced on a foundation construction site. On a medium-scale bridge foundation project with dozens of foundation piles, LRTK was trialed to improve work efficiency. Normally, a surveying team of 2–3 people would take more than half a day to locate pile centers and set foundation positions. The construction manager decided to personally adopt smartphone RTK surveying and perform pile center marking.

The manager uploaded the full list of pile design coordinates to LRTK Cloud the day before. The next day, he launched the LRTK app on site, loaded the pile coordinate data from the cloud, and began surveying. Holding the phone mounted on a monopod, he walked near each pile location and followed the on-screen guidance to fine-tune the position. At each pile point, the app displayed guidance such as “target point: ○ cm,” and he marked the ground with colored spray at the position where the display was nearly zero. He sequentially marked nearly 50 pile centers and completed the task in about 3 hours. The same work using the conventional method would be estimated at around 15 person-hours, whereas this was effectively one person working 3 hours. After the work, selected piles were re-checked with a total station, and all were within 1 cm (0.4 in) of the TS results—an excellent outcome. This demonstrated a work method that balanced efficiency and accuracy.

Moreover, the site benefited from smartphone RTK’s data-sharing effect. The marked pile coordinates were saved to the cloud in real time, enabling office engineers to immediately view all pile positions on the web and cross-check them with the design. Although they were prepared to request corrections if inconsistencies were found, all positions were within expected ranges. During pile-driving, pile head as-built measurements were taken with LRTK and shared to the cloud, allowing remote monitoring of construction accuracy from the office. The site supervisor commented, “Even inexperienced workers could mark pile centers accurately by following the phone guidance. On-site burden was greatly reduced, and as-built verification became much faster.” Smartphone RTK surveying is proving effective in practical construction and is gaining attention as a powerful means to achieve both labor savings and accuracy.

Conclusion: Innovate the site with the latest surveying technology

Smartphone and RTK–based surveying technology promises real transformation for foundation construction sites. The ability to survey at unprecedented speed and convenience while maintaining high accuracy is a considerable advantage for future site operations. This technology supports labor reduction and responsiveness without compromising quality, making it a strong ally for contractors facing labor shortages and schedule pressures.

From 2025 onward, industry shifts such as the mainstreaming of ICT construction in public works will mark a major turning point in digitalization. In this context, adopting smartphone RTK surveying will be a key to improving site productivity and competitiveness. Don’t be bound by the old notion that “surveying must be done with TS and craftsman skill”—try incorporating new technologies on site. You may feel uneasy at first, but with proper operation you will soon experience their convenience and effectiveness. Embrace the latest technologies and on-site know-how to drive surveying innovation, and realize safer, more efficient foundation construction. The future of the site is just around the corner—pick up the new tool of smartphone RTK and start building the next-generation site today.