Table of Contents

• What is RTK? Overview of Real Time Kinematic positioning

• Importance and challenges of surveying in utility construction

• RTK surveying of buried pipes (high-precision mapping of pipe routes)

• RTK surveying of manholes (recording cover location and elevation)

• RTK surveying of utility poles (efficient capture of structure locations)

• Effects of RTK adoption: labor reduction, shortened work time, improved safety

• Introducing simplified surveying with LRTK

• FAQ

What is RTK? Overview of Real Time Kinematic positioning

RTK stands for Real Time Kinematic, a high-precision positioning method using GNSS (Global Navigation Satellite Systems). Standard GPS or GNSS positioning can produce position errors on the order of several meters due to satellite signal errors. RTK surveying, however, uses two receivers—a base station (a receiver with a known, accurate coordinate) and a rover (the device being positioned)—and computes and applies the real-time differences between the satellite signals received by each. By receiving correction information broadcast from the base station, the rover cancels out errors from the atmosphere, satellite orbits, and receiver clocks, resulting in centimeter-level positioning (half-inch-level).

In Japan, a network-type RTK based on the Geospatial Information Authority of Japan's electronic reference station network (GEONET) is widely available. If the rover connects to a correction data distribution service via a system called Ntrip over the internet, it can receive real-time corrections without the need to set up your own base station. Using such network RTK services, a stable solution called a “fixed solution” can typically be obtained in several tens of seconds to about 1 minute, after which position updates can be maintained continuously with an accuracy of about 1-2 cm (0.4-0.8 in). Recently, the Cabinet Office’s quasi-zenith satellite “Michibiki” has introduced a centimeter-level (half-inch-level) positioning augmentation service (CLAS), enabling compatible receivers to receive correction signals directly from satellites and maintain high-precision positioning even in mountainous areas outside mobile coverage. This makes RTK positioning possible nationwide without relying on communications infrastructure, proving especially useful in disaster response and remote-area surveying.

RTK-GNSS technology has long been used in civil engineering and construction for tasks such as land boundary surveys, as-built verification, and machine guidance for heavy equipment, and its high-precision positioning is indispensable for improving productivity on job sites.

Historically, performing RTK surveys required expensive dedicated GNSS equipment and radio sets, and operation demanded specialist knowledge. Advances in technology have led to approaches known as “smartphone RTK,” which combine a smartphone or tablet with a compact GNSS receiver to perform RTK. This has drastically reduced initial costs from the hundreds of thousands of dollars range, and the miniaturization and simplified operation make centimeter-level positioning accessible to non-specialists.

Importance and challenges of surveying in utility construction

In utility (lifeline) construction carried out for roadworks, residential land development, and similar projects, it is critically important to accurately capture and record the locations of buried pipes, installed manholes, and aboveground utility poles. If the positions of buried water, sewer, or gas pipes are unclear, future maintenance or other construction can be impeded. Inaccurate location information for infrastructure such as utility poles and manholes can hinder rapid situational awareness during disasters and the digital management of urban infrastructure. For these reasons, there is an increasing demand to record accurate coordinates after construction in as-built drawings and ledgers, making surveying an essential part of infrastructure construction.

For example, sewer projects increasingly require finished drawings to specify manhole and pipe coordinates in a geodetic reference frame. Insufficient records of buried locations can lead to accidents such as accidentally damaging a gas pipe during later excavation, so accurate surveying is also important for safety management.

Traditionally, site staking and recording have been performed using tape measures and total stations. Recording the route of a buried pipe required repeatedly measuring offsets (distance and angle) from known points and plotting them on drawings, or measuring a manhole center from multiple site control points and calculating coordinates—procedures that were time-consuming. Utility pole positions were often estimated from right-of-way surveys or relative positions to existing features, which could lead to discrepancies between the as-built condition and drawings. These methods are time-consuming when performed manually, and accuracy can vary with worker skill; human errors like incorrect notes in field books or transcription mistakes later on are risks. Under tight schedules, surveying is sometimes deferred and once the pipe is buried, the exact location can become unknown.

With the Ministry of Land, Infrastructure, Transport and Tourism promoting *i-Construction*, there is a push to digitize and streamline infrastructure construction. In utility construction, it is desirable to preserve the locations of buried items and structures in three-dimensional coordinates for future GIS management and maintenance. One effective way to achieve this is high-precision GNSS RTK surveying. The following sections explain specific methods for measuring and mapping the locations of utility assets such as pipes, manholes, and utility poles using RTK and discuss the advantages.

RTK surveying of buried pipes (high-precision mapping of pipe routes)

When installing buried pipes—water, sewer, gas, etc.—it is necessary to record the pipe route as-built. Using RTK, continuous survey points can be captured by following the ground surface directly above the pipe, allowing high-precision mapping of the pipe’s alignment. For example, in open-cut construction, if you survey points on the ground directly above the pipe at regular intervals before backfilling, accurate 3D positions can be recorded later by supplementing the pipe diameter and burial depth. Measuring carefully at key points such as pipe bends and joints allows faithful reproduction of the piping network on drawings. Coordinates obtained by RTK are based on public coordinate systems (plane rectangular coordinates or geodetic latitude/longitude), making it easy to overlay them with other future survey results or GIS data. Compared to sketching on paper, positional accuracy improves dramatically, yielding digital records that can be used as geospatial information over the long term.

RTK pipe route surveying can be performed efficiently by a single person. Carrying a pole with a receiver mounted on your shoulder and walking along the trench allows many points to be collected in a short time even over long excavation sections. Distance measurements that previously required two people to measure with a tape can now be obtained directly as position coordinates by a single operator with RTK, greatly reducing labor. Systems that use a smartphone or tablet plot acquired points on a map in real time, making it intuitive to check for missed or unmeasured points. Another major advantage is that data can be saved and shared as digital files immediately after work, allowing as-built data to be organized for each pipe installation right away.

RTK surveying of manholes (recording cover location and elevation)

Manhole (access hole) locations can also be recorded accurately with RTK. If you align the pole tip with the center of the manhole cover and measure, you can obtain the plan coordinates with errors within a few centimeters (within a few inches). Where previously positions were calculated relative to site control points, RTK allows recording as absolute coordinates independent of those control points, enabling precise understanding of relative plan and elevation relationships among multiple manholes. Manhole cover elevation (top-of-cover elevation) is especially important in sewer systems. By applying a geoid correction to the ellipsoidal height obtained by RTK positioning, you can estimate the manhole cover elevation. Such 3D coordinate data are useful later for checking pipeline gradients and performing flow simulations.

If you use a smartphone-linked RTK system when surveying manholes, it is easy to take a photo of the cover on site and record it to the cloud along with the coordinates. Photos automatically include high-precision latitude/longitude and orientation metadata, making them convenient for later database searches. Centralized management of location and related information for the many existing manholes can greatly improve efficiency and sophistication of maintenance operations.

RTK surveying of utility poles (efficient capture of structure locations)

RTK is also powerful for measuring the positions of aboveground structures such as utility poles and signal poles. Although utility poles are installed at fixed locations, their mapped accuracy is not always high, and accurate as-built capture may be required for road widening or power-line burial planning. Mount a receiver on a pole and measure near the base of the utility pole to instantly record its installation coordinates. For tasks that require surveying many poles in sequence, RTK allows you to proceed quickly because you do not need to set a tripod at each point. Simply walking between poles and holding the antenna up to capture points sequentially dramatically increases the number of poles a single person can cover in a day.

Another advantage of RTK surveying is the ability to record photos and notes simultaneously. For example, photographing a pole’s ID plate and linking it to the coordinate data allows integrated management. Field-collected digital aggregation of information that previously required separate notes reduces post-return office work and helps prevent missing records. For as-built surveys of scattered structures like utility pole locations, these digital surveying methods particularly improve efficiency.

Effects of RTK adoption: labor reduction, shortened work time, improved safety

As described above, using RTK surveying on utility construction sites brings a variety of benefits. First is labor reduction. If single-person RTK surveying is possible, surveying work that previously required two to three people can be handled by one person. Even on sites without a resident experienced surveyor, construction managers can perform surveying themselves, increasing flexibility in staffing and reducing labor costs. Second is reduced work time. With RTK, which provides high-precision coordinates in real time, long wait times per point are unnecessary. Setup time is minimized and continuous point capture while moving allows wide-area as-built measurements to be completed in a short time. Recorded data are immediately digitized on site, reducing office redrafting work. Third is improved safety. Faster surveying reduces time spent on roads or in deep excavations, lowering the risk of traffic accidents and falls. Fewer workers on site also reduces contact opportunities, which is beneficial for infection control measures.

In this way, adopting RTK dramatically increases the productivity and safety of surveying operations and serves as a foundation for digital transformation (DX) on construction sites. In utility construction, the ability to reliably record the locations of buried asset that cannot be reworked later is particularly valuable for future infrastructure asset management.

Furthermore, 3D survey data obtained by RTK can help build construction models for CIM (Construction Information Modeling) and support future BIM/CIM initiatives.

Introducing simplified surveying with LRTK

Even understanding the usefulness of RTK, some may feel that acquiring traditional surveying equipment is a high hurdle. Against this background, a solution called smartphone-based LRTK has emerged and is transforming the RTK world. LRTK is a next-generation surveying system composed of a palm-sized compact GNSS receiver, a mobile app, and cloud services. Using a dedicated receiver “LRTK Phone” that attaches to an iPhone or Android device with one touch, the app receives network RTK via Ntrip or CLAS signals from satellites to achieve centimeter-level (half-inch-level) positioning. The system allows the entire workflow—from starting positioning to recording points, taking photos, and cloud saving—to be completed with a single smartphone, making it truly an “all-purpose survey instrument.”

By introducing LRTK, as-built surveying of utilities that previously required specialized equipment can be greatly simplified. With only a receiver and a smartphone, surveying can start immediately on site, and because LRTK is offered at an affordable price point, equipping multiple units at a site becomes realistic. In practice, LRTK enables one-person-per-device simultaneous surveying of pipe installations and road structures, eliminating bottlenecks even on large projects. Acquired data are automatically uploaded to the cloud, so by the time you return to the office, the survey points that form the basis of as-built drawings and ledgers are already organized. Daily operations can routinely produce 3D records including point clouds and photos for each site without special burden—this is the appeal of simplified surveying with LRTK.

LRTK cloud services allow centralized management of points and photos, and data can be downloaded in CSV or SIMA formats for easy import into CAD drawings or GIS software.

LRTK, which incorporates the latest technology, is designed to be usable even by non-specialists and achieves high-precision positioning with intuitive operation. For junior to mid-level technicians involved in utility construction, it represents a powerful new tool to strengthen on-site capabilities. If you have challenges recording the locations of pipes or manholes, consider introducing simplified surveying with LRTK to your site.

FAQ

Q: What do I need to start RTK surveying on site? A: Basically, you need an RTK-capable GNSS receiver and a communication environment that can receive correction information. If you use network RTK, you need an internet-connected device (smartphone or tablet), a compatible app, and subscription to a correction data distribution service. With systems like LRTK, you can start positioning simply by attaching a dedicated receiver to your smartphone and launching the app.

Q: Is RTK surveying possible outside mobile phone coverage? A: Yes. Network RTK that uses GSI’s electronic reference stations requires communication, but some LRTK receivers support CLAS signals from the Michibiki quasi-zenith satellites, allowing them to receive correction information directly from satellites and maintain centimeter-level (half-inch-level) positioning in mountainous areas or remote islands outside mobile coverage. Data acquired offline are stored on the device and can be synchronized to the cloud later when you return to coverage.

Q: Can RTK surveying really achieve centimeter-level accuracy? A: Under favorable conditions, accuracy within a few centimeters (within a few inches) can be expected. In open-sky environments, horizontal positions of about 1-2 cm (0.4-0.8 in) and vertical errors of about 2-5 cm (0.8-2.0 in) have been confirmed. Accuracy depends on satellite reception conditions, so better results are obtained by measuring where there are no tall buildings or trees nearby and by remaining stationary during positioning. Once a stable fixed solution is obtained, accurate positions can continue to be recorded even while moving.

Q: Can non-specialist users handle the equipment? A: Yes. Modern RTK systems are easy to operate, and basic point recording does not require advanced knowledge. For example, LRTK lets you tap desired points on a smartphone map to record them, and advanced settings are automated so beginners can become proficient in a short time. Because tasks that used to require separate devices or manual work—measuring, recording, and taking photos—are integrated, novices can reliably and efficiently capture as-built data without omissions.

Q: Isn’t the initial cost high? A: Compared to traditional high-end surveying equipment, systems using compact RTK receivers and smartphone apps are much more affordable. Specific pricing for LRTK varies by inquiry, but it is structured so you can start with an initial cost comparable to a single conventional GPS receiver. Even when equipping multiple devices, total cost tends to be lower than with traditional equipment, making it a cost-effective solution.

Q: Which smartphones are supported? A: Recent iOS (iPhone/iPad) and Android smartphones are supported. Any device that can physically attach an LRTK receiver and connect via Bluetooth or USB should work. Recommended environments include the latest iPhone series and high-performance Android models.

Q: Is it easy to share survey data and integrate with other software? A: LRTK automatically saves positioning data to the cloud for team sharing. Points can be exported from the cloud in CSV or SIMA formats for direct import into existing CAD drawings or GIS software. Compared to managing paper ledgers, data storage and sharing become far more efficient and secure.