How much can RTK reduce working time? Estimating effects by surveying and construction process

Table of contents

• Existing condition survey

• As‑built measurement

• Setting out (layout marking)

• Pile‑driving guidance

• Boundary surveying

• Volume calculation

• Photo records (construction photos)

• Simple surveying with LRTK

• FAQ

Introduction

Surveying and various measurements at construction sites require a lot of time and manpower. From existing condition surveys to as‑built inspections, setting out and guiding pile driving, and even confirming site boundaries, calculating earthwork volumes, and photographing construction records, these essential workflows have traditionally involved labor‑intensive tasks. In recent years, however, the construction industry has accelerated DX (digital transformation), and with initiatives such as i‑Construction, ICT technologies are beginning to be used in on‑site surveying and construction processes. Among these, RTK (Real‑Time Kinematic) positioning has attracted attention as a technology that dramatically improves surveying efficiency (shortening work time and reducing labor) and measurement accuracy.

RTK is a high‑precision satellite positioning technique that uses a base station and a rover to correct GNSS satellite signal errors in real time, allowing immediate acquisition of position coordinates with errors suppressed to several centimeters (several inches). Traditional surveying with total stations or levels required line‑of‑sight between points and multiple personnel, but with RTK positioning, absolute coordinates from satellites can be used so a single person can perform stakeout and measurements. Also, establishing control points can be simplified by using network RTK, greatly reducing the time needed for preparation.

So, how much can working time actually be reduced by introducing RTK? In one case study, ICT construction (RTK surveying and drone use, etc.) reduced the days required for initial road construction surveying from an average of 17.7 days to 2.7 days, reporting about a 70% reduction. If surveying processes are made this efficient, it directly shortens overall construction schedules and reduces labor costs.

This article estimates the efficiency gains RTK brings to each surveying and construction process. For major tasks—existing condition surveys, as‑built measurements, setting out (layout marking), pile‑driving guidance, boundary surveying, earthwork volume calculation, and photo records—we consider how much work time can be reduced by RTK and explore potential operational improvements. At the end, we also introduce a new, simple RTK solution using smartphones called “LRTK.”

Existing condition survey: efficiency gains from RTK

First, let’s look at the efficiency gains in preconstruction existing condition surveys (topographic surveys). Traditionally, two people work as a team with a total station on a tripod while another person holds a prism and measures each survey point one by one. On sites of several hectares, the number of survey points is large, and relocating equipment and securing lines of sight can be time‑consuming, often taking a full day.

This changes drastically when RTK positioning is introduced. After setting up a base station (or using network RTK), a worker can simply walk around with a rover receiver and observe terrain points one after another. For example, for a topographic survey of about 50 points, the work that traditionally took two people about half a day can, with RTK, be completed by one person continuously measuring within just a few hours in some reported cases. Of course, there is variation depending on the site’s GNSS reception environment and satellite availability, but under favorable conditions the time required for existing condition surveys can be reduced to a fraction of the previous time. This not only compresses the surveying time itself but also means tasks that previously required multiple personnel can be done by one person, reducing labor costs and the burden of scheduling.

Because RTK obtains coordinates in real time, data can be shared to the cloud immediately on site, and if points are missing they can be measured on the spot. This prevents “return trips” due to missed measurements and further improves overall work efficiency.

As‑built measurement: speeding up as‑built control

Next, the effect of RTK on as‑built measurements (as‑built surveys) after construction. As‑built control—verifying that completed structures such as road subgrade heights and installed components match design shapes and dimensions—is essential for quality assurance. Traditionally, surveying teams enter the site at each construction stage to measure heights and positions based on batter boards and benchmarks, which took time for inspection. For example, confirming the height of embankments required surveying staff to pick up points at fixed intervals and later generate drawings and compute differences in the office.

With RTK, as‑built inspections are also greatly streamlined. Construction personnel themselves can use smartphone‑mounted RTK receivers to measure key heights and coordinates immediately after construction and check deviations from design values on the spot, so inspections that used to take half a day can be completed in a very short time, enabling immediate decisions on rework. Point recording is also automated, reducing missed measurements and recording errors and eliminating the need for remeasurement. Furthermore, centimeter‑level accuracy (half‑inch accuracy) from RTK reduces human error, suppressing variation due to operator skill. In other words, consistent accuracy can be obtained regardless of who measures, allowing site supervisors and foremen to check as‑built conditions themselves and proceed to the next process without waiting for specialized surveyors. RTK positioning that balances quality control and efficiency brings large time savings and reduces rework in as‑built control.

Setting out (layout marking): labor savings in layout work

RTK also demonstrates strong benefits in setting out (layout marking) the positions of structures. Traditionally, dimensions are taken from drawings, reference centerlines and height controls are established on site, and multiple workers install batter boards with timber stakes and string lines to indicate the building outline. On tight sites or roadworks, this is hard physical labor and often requires repeated checks to ensure accuracy.

Using RTK can greatly reduce the labor for layout marking. If design data are loaded into a dedicated app on a smartphone equipped with an RTK receiver, a construction engineer can walk the site alone and mark the design coordinate positions. It is also possible for heavy equipment operators to confirm pile centers themselves using high‑precision GNSS, and layout work that used to require 2–3 people and more than half a day can in many cases be completed by one person in a short time. Fewer personnel also makes coordination with surrounding equipment operation easier and reduces hazardous work at openings or heights. Layout marking with RTK shortens work time and contributes to improved safety.

Pile‑driving guidance: efficient positioning of machinery

RTK has a major effect on guiding pile driving for bridge or building foundation piles. Traditionally, surveyors go to site to mark the intersection positions from drawings on the ground and direct heavy equipment operators. To prevent pile position errors, machines had to be stopped and locations checked repeatedly, and guiding a single pile could be time‑consuming.

With RTK, these pile center‑setting procedures are greatly simplified. By using a smartphone or tablet with a GNSS receiver, design pile center coordinates can be checked immediately on site, allowing workers to mark the correct location themselves and guide the piling rig. Combined with AR (augmented reality), it is also possible to overlay design positions on a smartphone screen while guiding. This significantly shortens the time required to check and correct pile positions and reduces machine idle time. If piles are set accurately from the first attempt, the risk of schedule delays due to rework is also reduced. RTK‑based pile guidance improves both construction accuracy and work speed.

Boundary surveying: shortening witness sessions

RTK is effective for boundary surveys conducted for public projects, land acquisition, and boundary confirmation with private landowners. Boundary confirmation involving neighbors or municipal officers should be completed smoothly on site. Traditionally, temporary benchmarks were established based on known point coordinates, and total stations were used to measure angles and distances to calculate boundary stake positions. Multiple remeasurements and calculations were often required, leading to long拘束 times for stakeholders.

With RTK surveying, once reference coordinates are established, a receiver can be held over each boundary point and a coordinate recorded with the push of a button, allowing multiple boundary points to be measured quickly. For stakeout, inputting precomputed boundary coordinates into a device and using navigation features can guide a single person to accurately reestablish boundary markers. Even in forests or undulating terrain where lines of sight cannot be secured, each point can be measured individually as long as satellites can be received, eliminating the need to clear lines of sight as with traditional methods. RTK boundary surveying shortens the time required for witness sessions and reduces the burden on both staff and attendees.

Because measurement point data are electronically recorded on site and saved to the cloud, coordinate calculations and drafting tasks are automated. As a result, the efficiency of the entire boundary confirmation workflow, up to the preparation of documents for municipal submission, improves dramatically.

Volume calculation: speeding earthwork computations with point clouds

Calculating volumes for embankments and excavations is also greatly streamlined with RTK. Earthworks require periodic measurement of remaining soil and backfill volumes for progress control and transport planning. Traditionally, surveying teams measured cross sections at fixed intervals and performed volume calculations back at the office. Creating cross‑section drawings and numerical calculations took time, resulting in a lag before results were available and delaying progress tracking.

With RTK, combined with drone aerial photography or 3D scanning, high‑density point cloud data can be acquired in a short time and volumes calculated immediately. For example, linking smartphone‑mounted LiDAR (laser scanner) with RTK positioning can generate a 3D model of the current terrain simply by walking and scanning the surroundings. Acquired point cloud data are automatically analyzed in the cloud, and embankment and excavation volumes are obtained instantly. Volume calculations that used to take more than half a day can be completed the same day, and measurement frequency can be increased, enabling daily visualization of construction progress.

Using RTK‑GNSS‑equipped drones also allows efficient aerial surveying of wide sites with minimal ground control points (GCPs), reducing effort for earthwork management at large reclamation sites. RTK accelerates volume calculation and significantly shortens the PDCA cycle for earthwork management.

Photo records (construction photos): streamlining data management

RTK‑enabled digitalization also benefits photographing and managing construction records. Before and after photos and photos of key processes must be taken numerous times and organized in a ledger by process, and this organization can be surprisingly time‑consuming. Traditionally, after photographing with a camera, locations and directions were noted for each photo, then photos pasted into a ledger and captions added in the office.

Current RTK‑based solutions automatically add location (geotag) and orientation information to photos and manage them mapped to plans or drawings. For example, photo data taken with smartphones or 360° cameras can be plotted on a cloud map immediately, saving the effort of later searching for “which location a photo corresponds to.” When integrated with photo ledger software, positioning data, shooting angle, and shooting location are automatically recorded and organized, reducing late‑night photo organization by site supervisors. By letting site workers focus on photographing and leaving data organization to digital systems, the time spent on photo record tasks can be drastically reduced. In addition, high‑precision RTK position data result in fewer mismatches when correlating photos with drawings or point clouds later, improving the reliability of construction records.

Simple surveying with LRTK: starting high‑precision positioning with a smartphone

Finally, we introduce LRTK, a solution gaining attention for enabling easy use of RTK technologies on site. LRTK is a surveying system consisting of an ultra‑compact RTK‑GNSS receiver that can be attached to a smartphone and a dedicated app, turning a handheld smartphone into a high‑precision surveying instrument. Its major feature is that without preparing dedicated heavy equipment, a smartphone alone can handle control point surveys, as‑built checks, and layout marking. For example, attaching an LRTK device to a smartphone and receiving network RTK correction information allows you to begin centimeter‑level surveying (half‑inch accuracy) as soon as you arrive on site. No complex equipment operation or cable connections are required, making it intuitive for anyone to use. Moreover, models that support Michibiki (QZSS) CLAS augmentation signals can continue high‑precision positioning even in areas without mobile communications, enabling stable surveying in previously difficult forested or mountainous sites.

The advantage of LRTK is not just miniaturization. By combining a smartphone camera and AR (augmented reality), surveying and construction management can be performed more intuitively. Using RTK‑derived self‑positioning as a reference, lines and structural models from design drawings can be overlaid on the real world, making it immediately clear through the screen “what to place here.” Even complex drawing interpretation or installing batter boards is unnecessary: simply pointing a smartphone lets you verify precise stakeout positions, allowing inexperienced workers to locate positions without error. Smartphone RTK solutions like LRTK democratize high‑precision positioning for more site staff and realize “simple surveying” that can be performed with fewer people.

To maximize the time‑saving effects introduced above, tools must be easy for everyone to use. In that regard, the LRTK series is a cutting‑edge solution compatible with i‑Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism and could become a trump card for on‑site DX from surveying to construction management. If you are considering RTK for labor saving and efficiency improvements, consider adopting smart surveying with LRTK.

FAQ

Q: How accurate is RTK positioning? Is it comparable to a total station? A: Generally, RTK‑GNSS can achieve about 1–3 cm (0.4–1.2 in) horizontal accuracy and about 3 cm (1.2 in) vertical accuracy in open environments. While it does not offer the millimeter‑level exactness of optical total stations, it provides sufficient accuracy for many civil surveying and construction management tasks. Considering the ability to measure wide areas at once and the advantage that global positioning does not accumulate errors between control points, RTK delivers practically comparable results. However, accuracy can degrade due to multipath (signal reflections) or signal blockage near tall buildings or trees, so selecting an open site for RTK surveying is advisable.

Q: Do you need special skills or certification to use RTK surveying? Can one person handle it? A: No special national licenses are required specifically to operate RTK surveying. With basic knowledge of equipment operation and positioning principles, people other than licensed surveyors can operate it. Unlike traditional total stations, RTK does not require an assistant to hold a prism, and in principle one‑person operation is possible. On‑site positioning apps provide guidance, so advanced skills such as instrument leveling or angle reading are not required. However, judging the accuracy of obtained coordinates and reflecting survey results in drawings does require some knowledge of surveying standards and coordinate systems. For official survey deliverables, it is still advisable to perform work under the supervision of a licensed surveyor as before.

Q: Can RTK surveying be done in areas without network connectivity, such as mountain regions? A: Yes. Network RTK correction information typically uses mobile communication networks, but in areas without mobile coverage you can use Michibiki’s QZSS CLAS augmentation signal. CLAS‑compatible RTK receivers can receive satellite‑based corrections and maintain centimeter‑level positioning even in communication‑dead mountain areas. However, in environments like dense forests where sky visibility is poor, satellite signals themselves may not be receivable and RTK solutions may not obtain a fix. In such cases, strategies like temporarily moving to an open area to survey and transferring positions relatively, or combining with traditional methods, may be necessary.

Q: RTK equipment seems costly to introduce—does it provide a good return on investment? A: Introducing RTK requires initial investment in receivers and possibly subscription services for correction data, but the efficiency gains often justify the cost. For example, if a survey that used to require two people for a day can be done by one person in a few hours, labor cost savings are significant. Recently, low‑cost smartphone‑compatible RTK receivers and monthly subscription correction services have become available, so high‑precision positioning can be used without the hundreds of thousands of yen investments of the past. Considering productivity improvements and labor reductions on site, the cost‑performance of RTK introduction is generally very high.

Q: Does RTK make total stations and levels unnecessary? A: RTK streamlines many surveying tasks, but traditional instruments still have their roles depending on the situation. For example, in tunnels or inside buildings where satellite signals cannot reach, total stations and levels remain indispensable. Also, for short‑range measurements requiring millimeter‑level control such as precise leveling or equipment installation surveys, optical instruments can be more reliable. Therefore, rather than completely replacing existing equipment, it is recommended to use RTK for outdoor wide‑area surveys and complement fine‑detail precision measurements with optical instruments. Using both appropriately improves overall surveying productivity and accuracy.