Centimeter-level accuracy (cm level accuracy (half-inch accuracy)) without a base station! Revolutionizing land and building surveyors’ surveying style with LRTK

The surveying field for land and building surveyors is now on the cusp of a major transformation. Until now, high-precision surveying invariably required RTK positioning with a base station. However, a newly introduced technology, LRTK (RTK positioning technology that does not require a base station), is ushering in an era in which centimeter-level positioning can be obtained in real time without preparing a dedicated base station at the site. The previously fanciful idea of “centimeter-level accuracy without a base station” is becoming a reality. This promises unprecedented flexibility and efficiency in surveying workflows for land and building surveyors.

In this article, we first review the mechanism and constraints of conventional RTK surveying, then explain the mechanism of LRTK and how it achieves centimeter accuracy through satellite augmentation. We will also delve into how eliminating the need for a base station makes field response more flexible and rapid. Next, we present examples of LRTK applications across various surveyor tasks such as boundary determination, as‑is surveys, restoration of parcel boundaries, and public–private consultations, and consider improvements in safety and future potential enabled by a new, small-team, short-duration surveying style. Finally, we touch on the benefits of introducing simple surveys using LRTK. Let’s take a look at the full picture of this new surveying revolution.

Mechanism and constraints of conventional RTK surveying that requires a base station

In conventional RTK (Real Time Kinematic) surveying, two GNSS receivers — a base station and a rover — were required for error correction, and correction information had to be transmitted from the base station to the rover in real time. The base station is installed at a known coordinate point, errors in the signals received from satellites are calculated, and correction data are distributed to the rover via radio communication or the Internet. The rover uses this correction information to correct its solution in real time, reducing errors that would be several meters (several ft) with standalone positioning to a few centimeters (a few in). Such RTK technology has made precise placement of boundary points and the like possible.

However, the conventional method also has several challenges. The main constraints include:

• High equipment cost: High-precision GNSS receivers must be procured as a pair for the base station and rover, making the initial investment large. Conventional integrated RTK-capable GNSS equipment can cost several million yen per unit, and it was a burden for surveying offices to own multiple units. Using commercial correction services also incurs running costs such as annual subscription fees.

• Dependence on communication environment: Real-time corrections require data transmission from the base station to the rover, using UHF low-power radios or cellular networks. In mountainous areas or locations with poor radio coverage, communications can be unstable, and inability to receive correction information risks degraded positioning accuracy. Network RTK solutions (such as VRS) also require constant mobile connection, so they do not function in underground or forested areas outside cellular coverage. Moreover, when the base station and rover are too far apart, correction effectiveness diminishes, necessitating relocation of the base station when surveying wide areas.

• Large-scale transport and setup of equipment: Equipment for a base station — tripods, mounting platforms, batteries, and communications devices — entails considerable preparation and setup effort. Transporting heavy equipment to distant sites is burdensome, and installing and managing it alone is difficult. Leaving a base station deployed for long periods also raises concerns about theft and equipment monitoring.

Centimeter accuracy of LRTK realized by satellite augmentation signals

So how does LRTK achieve centimeter accuracy without a base station? LRTK receives wide-area error correction information via satellites and performs correction processing within the receiver to enable high-precision positioning. Specifically, in addition to signals from GPS and multiple GNSS constellations, the receiver simultaneously obtains satellite augmentation signals (data that augment satellite positioning). A dedicated high-performance chip then performs real-time computations to correct satellite orbit and clock errors, ionospheric and tropospheric delays, and other factors, dramatically improving positioning accuracy.

A representative augmentation signal available for LRTK use in Japan is the Quasi-Zenith Satellite System “Michibiki” centimeter-class positioning augmentation service (CLAS). LRTK-capable GNSS receivers can receive Michibiki’s L6-band signal to achieve centimeter-level positioning across the country. CLAS generates wide-area common error information based on observation data from networks such as the Geospatial Information Authority of Japan’s continuous GPS reference stations, and this information is broadcast from satellites. In other words, users can obtain RTK-equivalent accuracy in real time simply by receiving correction data from the Michibiki satellites, without individually setting up base stations. LRTK measurement accuracy is reported to be approximately ±1–2 cm (±0.4–0.8 in) horizontally and about ±3 cm (±1.2 in) vertically, which is comparable to Class 1 GNSS surveys based on national reference points.

With this system, centimeter-level positioning can be performed even at sites outside cellular coverage such as mountainous areas or agricultural land on urban outskirts, by directly obtaining augmentation information from overhead satellites. LRTK receivers are equipped with high-sensitivity, multi-GNSS, multi-frequency antennas that can track satellites near the horizon, stabilizing accuracy. By leveraging the latest high-precision positioning algorithms (known as PPP‑RTK), it is possible to obtain stable position information with errors of only a few centimeters from a single receiver.

Flexible field response and mobility enabled by eliminating the base station

One of the first benefits of LRTK adoption is the high portability of equipment in the field. There is no need to carry heavy tripods or large batteries for a base station; surveys can be completed with a palm-sized GNSS receiver and a tablet or smartphone. This allows surveyors to move nimbly between points even in forest boundary areas or on residential land with many level changes. Transporting equipment by public transit or for distant site visits becomes much less burdensome, making it easier for female or elderly surveyors to handle. Eliminating bulky equipment also removes constraints on set-up space in narrow urban lots.

Moreover, not needing to set up a base station dramatically increases on-site responsiveness. Surveying can begin immediately upon arrival without complex setup, enabling efficient work even for short-duration tasks. If additional points need to be measured unexpectedly, equipment can be taken out and measurements started on the spot, allowing flexible response to changing conditions. Without concerns about base station placement or securing communications links, the ability to capture the point you want exactly when you want it—the lighter “footwork”—is a unique strength. In this way, LRTK significantly enhances surveyors’ field responsiveness and expands the freedom of survey planning.

Examples of LRTK applications in land and building surveyor work

High-precision positioning using LRTK is useful across many tasks surveyors regularly undertake. Specific application scenes include:

• Boundary determination: For installing or checking boundary markers, LRTK enables quick and accurate measurement of boundary point coordinates. Even in situations that previously required carefully setting up a base station, LRTK allows immediate measurement after equipment setup, streamlining field surveys. A single person can measure multiple boundary points in sequence, making small-team boundary inspections easier. Because points can be recorded directly in geodetic coordinates, it is also easy to compare with cadastral maps and existing coordinates to understand boundary locations. Boundary markers hidden by vegetation or buried under pavement can also be located using coordinate information with accuracy of several centimeters (several in).

• As‑is surveys: LRTK excels in detailed surveys for producing as‑is site plans. A single operator can nimbly measure many fine survey points—building perimeters, road shapes, terrain break points—without splitting tasks, collecting necessary data in a short time. Previously, total stations required a team with a tripod operator and a prism handler, but LRTK allows one person to acquire point data. Coordinates obtained are plotted in real time on a tablet map, allowing on-site checks for omissions or missed points; since observation data are already digital, no manual data entry is needed after returning to the office, enabling immediate drafting and report preparation.

• Restoration of parcel boundaries: Even if boundary markers have been lost for some reason, LRTK can rapidly assist in restoring parcel boundaries. Nearby known points (for example, adjacent boundary markers or building corners) can be measured on-site and calculations performed immediately to derive the position of lost points from their coordinate relationships. Because absolute coordinates from satellite positioning are available, long traverses or extensive surveys are not required to estimate original boundary positions with high accuracy. This is particularly efficient in forested areas or other locations with poor sightlines, where LRTK can quickly obtain surrounding reference points to restore parcel boundary points. If boundary coordinates were recorded in the past, they can be instantly verified in the field with LRTK, facilitating consistency checks with official data.

• Public–private consultations: In boundary confirmation or joint inspections between private and public landowners, LRTK is a valuable tool. Surveyors can measure points near boundaries on-site and immediately share results with stakeholders, conveying boundary positions that are difficult to grasp from documents or drawings alone through concrete numbers and visuals. For example, by preloading existing boundary line data onto a tablet, measured points can be compared on-screen and the boundary line displayed for group confirmation. In some cases, AR overlays of boundary lines via a smartphone or tablet camera can make the boundary appear projected on the ground, helping stakeholders intuitively understand positional relationships. The ability to present accurate survey data on site contributes greatly to smooth public–private consultations and consensus building. Objective data-based explanations resolve misunderstandings on the spot and help prevent unnecessary boundary disputes.

New surveying style completed by small teams in short time and improved safety

As LRTK becomes more widespread, team composition and work time are changing dramatically. Tasks that previously required two to three people can increasingly be completed by a single person with LRTK and a mobile device. Reducing personnel not only increases operational efficiency but also makes scheduling easier and allows more nimble handling of projects. On-site work time is also trending shorter; for instance, simple boundary checks or quick as‑is surveys can now yield results in far less time than before.

Safety benefits should not be overlooked. Compared with traditional styles that deployed many people carrying equipment along roadways, compact equipment and short-duration surveys reduce risks such as traffic accidents or heat stroke. Reducing heavy equipment handling and long installation times at hazardous spots lowers physical strain on workers. Fewer occasions requiring tripod setup in narrow alleys or night-time installation and removal in poor visibility also improve third-party safety. LRTK’s streamlined surveying methods contribute not only to efficiency but to enhanced on-site safety.

The expanding future of surveying technology: possibilities brought by LRTK

The new surveying style opened up by LRTK is expected to evolve further. For example, combining high-precision GNSS positioning with drone photogrammetry or mobile LiDAR makes rapid 3D surveying of vast land areas more realistic. In practice, efforts are underway to combine small GNSS receivers with 360° cameras or laser scanners to capture the entire site for drafting. If technologies like LRTK become commonplace, each surveyor could operate as a high-precision “mobile surveying station,” dramatically improving survey speed and quality.

As positioning satellites and augmentation signals are further improved, positioning environments in urban canyons and mountainous areas are also expected to get better. If centimeter-level positioning becomes routinely available, the nature of boundaries and surveying itself may change. Workflows such as sharing survey data obtained on site in the cloud and having remote stakeholders simultaneously review and make decisions may also become standard. In the industrywide DX (digital transformation) movement promoted by initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s i‑Construction, high-precision positioning tools like LRTK will play an important role. Advances in high-precision positioning technologies, including LRTK, will further raise the operational efficiency and service quality of land and building surveyors.

Conclusion

LRTK, which achieves centimeter-level accuracy without a base station, has the potential to transform surveying styles for land and building surveyors. By eliminating heavy equipment and complicated procedures, it offers not only cost reduction and time savings, but also multi-faceted benefits such as greater flexibility and improved safety. Using this easy-to-deploy accuracy tool can dramatically improve workflow efficiency from boundary determination to various surveys, directly enhancing service quality for clients.

Now that high-precision positioning is no longer limited to specialized equipment, surveyors who proactively adopt new technologies can provide higher value services. A new surveying revolution that frees practitioners from base station constraints has already begun. By combining the experience and knowledge cultivated over the years with LRTK-enabled smart simple survey styles, why not apply these advances to future surveying operations? This new step will greatly expand the possibilities of your practice.