Is GPS insufficient? Achieving full-fledged high-precision positioning with LRTK

Recently, opportunities to determine position with GPS built into smartphones and car navigation systems have increased. GPS, which makes it easy to know your current location, is convenient, but its positioning accuracy is generally on the order of several meters. For precise stakeout and surveying tasks required on civil engineering and construction sites, this level of accuracy is often insufficient. Is GPS insufficient? This article explains the limits of conventional GPS-only positioning, the need for high-precision positioning, and how the latest technology, LRTK, can be used to achieve centimeter-class full-fledged high-precision positioning. Please read on for tips to streamline surveying operations on-site. At the end of the article we answer questions in FAQ format to help deepen your understanding of simplified surveying using LRTK.

Table of Contents

• Limits of GPS standalone positioning

• Scenes that require high-precision positioning

• What is real-time correction positioning (RTK method)?

• What is LRTK that enables high-precision positioning

• Features and benefits of LRTK

• Main use cases of LRTK

• Comparison with conventional positioning methods

• Simplified surveying with LRTK

• FAQ

Limits of GPS standalone positioning

Standalone positioning using commonly used GPS (Global Positioning System) typically incurs errors of about 5–10 m (16.4–32.8 ft). This is because signals from GPS satellites are affected by the atmosphere and the ionosphere, and various factors such as clock errors and orbital errors cause deviations in positioning. If you only need to understand your location on a map, an error of several meters may not be a problem. However, for tasks such as quality control in civil engineering work or confirming land boundaries, where centimeter-level accuracy is required, standalone GPS accuracy is not sufficient. Many people have experienced checking position information obtained from a smartphone’s GPS on an actual site and finding it “off by several meters from where I thought it was.” As shown here, standalone GPS positioning has limitations, and more precise positioning requires additional correction technologies.

Scenes that require high-precision positioning

On construction and surveying sites, even slight positional deviations can lead to major problems. For example, if stakeout for foundation work is off by several tens of centimeters, it can affect the accuracy of the entire structure. Also, if errors are large when calculating earthwork volumes during as-built surveys, the management of construction progress and quantities can be skewed. Land boundary stake placement and land surveying cannot indicate exact boundaries with errors of several meters. Thus, high-precision positioning is indispensable to ensure safe and reliable construction and accurate surveying results. In recent years, initiatives to improve construction quality and efficiency using ICT, such as *i-Construction* advocated by the Ministry of Land, Infrastructure, Transport and Tourism, have been progressing, raising expectations for tools that can easily obtain high-precision positional information.

What is real-time correction positioning (RTK method)?

Real-time error correction is the key to achieving centimeter-level accuracy with GNSS positioning including GPS. A representative technique is the RTK method (Real-Time Kinematic). In RTK, observation information is exchanged between a reference station with known accurate coordinates and a receiver on the moving side (rover) to correct satellite positioning errors in real time. This can reduce position errors that are normally on the order of several meters down to a few centimeters or less. RTK usage styles include setting up your own reference station, or receiving correction data from a network of multiple reference stations installed regionally, known as network RTK. In Japan, the quasi-zenith satellite system “Michibiki” provides a centimeter-class augmentation service (CLAS), and using this service allows you to receive high-precision correction information even in environments where Internet communication is difficult. RTK positioning uses carrier-phase measurements of satellite signals and requires an initialization period (resolving integer ambiguity) of several tens of seconds, but once a solution called a Fix solution is obtained, stable centimeter-level positioning is possible thereafter.

What is LRTK that enables high-precision positioning

The recently introduced LRTK is a next-generation solution designed to make RTK-style positioning easier to use. Small GNSS receiver devices that can be used in combination with smartphones are at the center of LRTK. By attaching a pocket-sized receiver to a smartphone and launching a dedicated app, you can perform real-time correction-based high-precision positioning without complicated equipment layouts or advanced settings. In short, LRTK was developed as a “surveying instrument that anyone can use in their pocket.” It revolutionizes RTK surveying, which traditionally required fixed reference stations, large surveying instruments, and dedicated surveying controllers, enabling it with the simple configuration of just a smartphone plus a small receiver. When you power on a dedicated terminal, it automatically starts receiving correction information and reaches a centimeter-class Fix solution in about 20–30 seconds. After that, you can instantly record coordinates (latitude, longitude, and height) of any point simply by tapping a button in the app. Because it can be operated intuitively without specialized knowledge, on-site staff of any level will be able to handle full-fledged high-precision positioning.

Features and benefits of LRTK

Summarizing the points where LRTK outperforms conventional surveying methods:

• Centimeter-class high accuracy: LRTK devices support RTK-GNSS and achieve positioning errors within a few centimeters. This is overwhelmingly higher accuracy compared to standalone GPS; in experiments the difference between measurements of the same point taken with a high-performance GNSS surveying instrument and LRTK was only on the order of a few millimeters. By averaging multiple observations as needed, per-point errors can even be reduced down to the millimeter level.

• Easy setup: No complicated equipment installation is required. Without preparing your own reference station or installing large antennas, simply attach the LRTK terminal to your smartphone and power it on; it will automatically receive correction information. High-precision positioning can begin in about 20–30 seconds, and you record the desired point by pressing a button—no need to worry about specialized configuration tasks.

• Compact, lightweight, and highly portable: The receiver body is compact enough to fit in the palm of your hand and weighs about 125 g. It can be attached to a smartphone and carried in one hand, allowing you to easily obtain measurement points while walking around the site. It runs for long periods on its internal battery and is waterproof, dustproof, and shock-resistant, so it can be used with confidence in harsh outdoor environments.

• Stable surveying by one person: By using the dedicated pole (monopod) and smartphone holder included in the starter kit, one person can stabilize the terminal vertically for measurements. There is no need to carry heavy tripods or have an assistant hold a prism as in the past. In narrow sites or when surveying at heights or on slopes, the mobility of LRTK enhances efficiency.

• Real-time data utilization: A system is in place for saving and sharing acquired measurement data to the cloud at the same time as positioning. Results measured on site can be shared instantly with the office for checks or instructions for additional measurements. Also, LRTK offers extensions that integrate smartphone cameras and AR functions to tag photos with accurate position information or perform simple 3D scanning to model terrain.

• License-free and low cost: LRTK communication uses Bluetooth and Internet connections, so no dedicated radio license is required. Anyone can start without legal hurdles. Initial costs are kept far lower than conventional high-precision positioning equipment (which can cost several million yen), making adoption affordable even for small sites. Correction information can be used without additional fees if you utilize the CLAS signal from Michibiki, so running costs are minimal.

Main use cases of LRTK

With LRTK enabling “easy high-precision positioning,” various new approaches emerge for on-site tasks. Main use cases include:

• As-built measurement on construction sites: As-built (volume) management traditionally performed by experienced surveyors using total stations can be quickly measured by site staff using LRTK. For example, you can measure the height and slope of excavations and embankments on the spot and immediately confirm construction accuracy. If measurement data is shared to the cloud in real time, construction managers at a remote site office can check it immediately.

• Boundary measurement and land surveys: Coordinates of boundary points and survey marks can be accurately obtained on site and shared immediately. Tasks such as measuring boundary lengths with adjacent land and comparing them with drawing values, or navigating to positions for new boundary stake placement, can be done efficiently with LRTK. Work that previously required expensive surveying equipment can be completed with just a smartphone and LRTK, reducing costs and shortening work time.

• Disaster site situation recording: In disaster sites affected by earthquakes or heavy rain, rapid and accurate recording and sharing of damage information is required. With an LRTK starter kit you can tag photos taken with a smartphone with centimeter-precision location information and upload them to the cloud for real-time sharing with relevant organizations. Even in areas where communication infrastructure is cut off, LRTK can receive correction information directly from Michibiki’s CLAS signal, making it powerful for understanding isolated sites.

• Improving accuracy of drone surveying and photogrammetry: LRTK is also effective for aerial photogrammetry and mapping. Accurate measurement of ground control points (GCPs) is essential to generate precise 3D models from photos taken by drones. Using LRTK, many GCPs can be measured in a short time, significantly enhancing the accuracy of photogrammetric stitching. There are also use cases where personnel equipped with a helmet-mounted smartphone + LRTK walk through hazardous areas to acquire surrounding point cloud data. Combining aerial data from drones with detailed ground surveys enables safe and highly accurate situation assessment.

Comparison with conventional positioning methods

The new positioning style enabled by LRTK has many advantages over conventional methods. Here we compare them in terms of equipment configuration, accuracy, cost, and personnel requirements.

• Differences in equipment and effort: Conventional RTK surveying required carrying and installing a full set of fixed reference station equipment (receiver, antenna, tripod), a rover receiver plus a dedicated controller, and radio devices connecting them—several large pieces of equipment. Preparation before starting surveying also took time and effort. In contrast, LRTK uses a simple setup of a smartphone and a palm-sized receiver, allowing measurements to begin quickly at any time. Without heavy tripods or fixed equipment to carry, surveying while moving or working in confined spaces becomes far more efficient.

• Positioning accuracy and stability: For public surveying and scenes requiring millimeter-level accuracy, large high-performance GNSS receivers or total stations are still indispensable. However, for accuracy required in typical construction management and surveying tasks, LRTK is sufficient. If operated properly, both horizontal and vertical accuracies within a few centimeters can be obtained, and in some cases the difference from total station surveys is on the order of a few millimeters. Considering the advantages of real-time data sharing and ease of operation by anyone, LRTK can often surpass conventional methods in improving overall on-site productivity.

• Cost and introduction hurdles: Equipping conventional precision surveying devices could require initial investments on the order of several million yen, and there were high hurdles such as learning to operate the equipment and obtaining radio station licenses. The LRTK starter kit is offered at a price point that is much easier to introduce (please inquire for pricing). You can start centimeter-class positioning without investing hundreds of thousands to millions of yen. Operating costs are also low: if you use Michibiki’s CLAS for corrections there is no additional fee, and network RTK can use existing cellular communication to keep costs down. No radio license is required because Bluetooth and existing networks are used—if you have a smartphone and the device, you can start centimeter-level positioning today.

• Required personnel and skills: Previously, surveying was typically carried out by teams of two or more (instrument operator and staff), and certified personnel (such as surveyors) needed to be present. After introducing LRTK, many measurement tasks can be completed by a single worker without special qualifications (note: official public survey results submitted for public works should be conducted under the supervision of a qualified surveyor). If each on-site worker can position with a smartphone and LRTK, delays due to waiting for surveying can be eliminated and a “measure when needed” workflow becomes possible. The one-person-one-device style can be a trump card for maintaining both productivity and accuracy in sites with severe labor shortages.

Simplified surveying with LRTK

With the advent of LRTK, the conventional notion that “high-precision surveying is only handled by specialists” is changing dramatically. Attach a dedicated receiver to your smartphone, power it on, and it will automatically start receiving correction information—then just press the button at the location you want to measure. The removal of time-consuming surveying preparations means centimeter-class positioning is possible anytime, anywhere, which is revolutionary.

Moreover, LRTK is compact and easy to carry, and is resistant to water, dust, and shocks, so it can be casually brought to any site. Measurement data is saved to the cloud and shared instantly, smoothing information transmission between the field and the office. For these reasons, LRTK is a powerful tool to support the DX (digital transformation) of on-site operations. Its price is also far more accessible than conventional high-precision equipment, making it ideal as a first high-precision positioning tool. Users familiar with smartphone operation can master it quickly, so even surveying novices can become field assets.

By introducing LRTK—the “surveying instrument that measures immediately with a smartphone”—on-site surveying operations can be dramatically streamlined. Surveying, which used to be left entirely to specialists, becomes more familiar, and high-precision measurements become possible even with small teams. Why not evolve your site to the next stage with simplified surveying using LRTK?

FAQ

Q1. Can LRTK really achieve accuracy of a few centimeters? A1. Yes. In environments where satellites can be properly received, LRTK provides positioning accuracy within a few centimeters both horizontally and vertically. In experiments, when comparing measurements of the same point taken with high-performance GNSS surveying instruments, the error between LRTK results and those instruments was within a few millimeters to about 1 cm. This meets the accuracy generally required on construction sites, confirming that centimeter-level precision is truly achievable.

Q2. Is special equipment like a reference station required? A2. No. LRTK achieves high-precision positioning by receiving correction data distributed over networks or by directly receiving the Michibiki CLAS signal. Users do not need to set up their own base station; a smartphone and an LRTK terminal are sufficient with no additional hardware required. Because the dedicated terminal automatically obtains correction information, there is no need for radio station licenses or complicated apparatus as in the past.

Q3. Can it position in places without cellular reception? A3. Yes. LRTK terminals support the Michibiki centimeter-class augmentation service (CLAS), so positioning can continue by directly receiving correction information from satellites even in mountain areas or disaster sites where cellular communication is out of range. As long as Michibiki satellites are visible overhead, centimeter-level positioning is possible without Internet connectivity. However, if satellite signals themselves are obstructed by buildings or cliffs, reception may be difficult, so maintaining a suitable positioning environment is necessary.

Q4. Are specialized knowledge or qualifications required to operate it? A4. No, it is designed to be used without special knowledge. You can perform measurements simply by following the smartphone app screen and pressing buttons, so people unfamiliar with equipment handling can start using it immediately. Also, no radio operator license is required to use LRTK. Note, however, that if measurement results are to be used officially as public surveying outcomes, they must be conducted under the supervision of qualified surveyors; for typical on-site work, unqualified personnel can use LRTK without issue.

Q5. Can one person perform surveying tasks? A5. Yes. LRTK is designed for single-person use. By using the dedicated pole and smartphone holder, you can securely fix the receiver and smartphone and perform stable surveying alone. You simply move to the desired location, set the terminal, and press the record button in the app, so there is no need for an assistant as before. Field sites that have actually introduced LRTK have succeeded in reducing personnel and improving surveying efficiency.

Q6. What is included in the LRTK starter kit? A6. The LRTK starter kit includes the LRTK main high-precision GNSS receiver and various accessories to support on-site surveying. Specifically, it contains a dedicated monopod (telescoping pole) for mounting the receiver, replacement metal tips, a smartphone holder that attaches to the pole, a spirit level with a bubble for confirming the pole’s verticality, and a shoulder bag to store the equipment. These accessories are not mandatory but help stabilize the equipment to ensure accuracy and support one-person surveying.

Q7. How much does introduction and operation cost? A7. LRTK is priced to be much more accessible than conventional professional surveying equipment (please contact us for pricing details). The ability to start centimeter-class positioning without investments on the scale of several million yen is a major advantage. Regarding operating costs, using Michibiki’s CLAS for corrections incurs no additional fee, so maintenance costs are limited to communication expenses. Even when using network RTK services, existing cellular communication can be used to keep costs low.