RTK GPS Comparison: High Precision Made Easy! The Low-Cost Power of LRTK

Table of Contents

• What is RTK GPS?

• Traditional RTK positioning methods and challenges

• What is LRTK?

• Features and benefits of LRTK

• What you can do with LRTK

• Comparison of LRTK and traditional systems

• Use cases for LRTK

• Summary

• FAQ

What is RTK GPS?

RTK (Real Time Kinematic) GPS is a technology that enables centimeter-level high-precision positioning by correcting satellite positioning errors in real time. Ordinary GPS (GNSS) positioning makes it difficult to achieve the accuracy required for construction and surveying. Typical smartphone-integrated GPS can have errors of about 5–10 m, which is sufficient for map-based location checks but unsuitable for precise positioning or elevation measurements. By contrast, the RTK method can pinpoint position with extremely high accuracy within a few centimeters. Achieving high-precision positioning enables more efficient and accurate location setting in surveying and civil engineering work than conventional methods.

The basic principle of RTK positioning is relative positioning using two receivers. One unit is set up at a known point as a base station, and error information from satellites is exchanged with a second unit, the rover. The base station sends the error data it acquires to the rover, and the rover applies corrections so that positioning errors that would be several meters on their own can be reduced to a few centimeters. In other words, RTK is a technology that dramatically improves GPS accuracy through real-time differential corrections.

Traditional RTK positioning methods and challenges

To achieve high-precision RTK positioning, dedicated high-performance GNSS equipment has traditionally been used. For example, surveying RTK-GNSS receivers typically require a pair of units—one for the base station and one for the rover—each set up on site and communicating correction information via radio or network. While this method enables high-precision position measurement, there have been several operational challenges.

First, the initial cost is very high. Dedicated RTK-GPS surveying equipment generally costs several million yen, making it difficult for small- to medium-sized businesses or individuals to adopt easily. The equipment often comes with many accessories such as batteries, tripods, and dedicated controllers, making it bulky and heavy, and cumbersome to transport and set up at job sites. Many devices are difficult to handle without surveying experience, so specialized knowledge and training have often been required.

Furthermore, traditional RTK positioning has been dependent on communication environments. It can only be used within the range of radio communication between the base station and rover, and when using network-based RTK services (such as VRS), stable mobile communications (mobile internet) at the site are essential. In mountainous or out-of-coverage areas, RTK may not be usable, and in disaster sites where infrastructure is disrupted, high-precision positioning may be impossible.

Thus, the major hurdles of conventional RTK positioning systems have been that “expensive, large-scale equipment is required to obtain high precision” and that “they cannot be used depending on site and environment.”

What is LRTK?

LRTK was developed to solve these issues and to provide high-precision positioning easily. LRTK is a new RTK positioning solution that combines a smartphone with a compact high-precision GNSS receiver. It was developed to make RTK positioning, which used to be large and expensive, more compact and low-cost.

Specifically, LRTK consists of a lightweight, compact GNSS receiving device that attaches to a smartphone (currently mainly iPhone) and dedicated surveying apps and cloud services. By leveraging the mobility of smartphones and familiar user interfaces, GNSS receiver-acquired high-precision positioning data can be used in real time within a smartphone app. In short, the concept of LRTK is “turning your smartphone into a high-precision positioning device,” enabling centimeter-level positioning without special equipment or complicated operations.

The name LRTK also implies “Low-cost RTK,” and true to its name, it is a solution that greatly reduces initial deployment costs compared to traditional systems. The technology was developed by a venture originating from the Tokyo Institute of Technology and has recently begun to attract attention in construction and surveying fields.

Features and benefits of LRTK

LRTK offers various features and advantages not found in traditional RTK systems. The main points are as follows.

• Small, lightweight, and portable: The LRTK GNSS receiver (LRTK Phone device) weighs about 165 g and is only about 1 cm (0.4 in) thick. It is nearly the same size as a smartphone and can be attached to the back of an iPhone using a dedicated case. Compared to conventional large surveying equipment, it is overwhelmingly compact and easy to carry to job sites.

• High-precision positioning performance: LRTK can achieve accuracy of ±1–2 cm (±0.4–0.8 in) horizontally and about ±3 cm (±1.2 in) vertically. Single short-duration fixes typically stay within about 1.2 cm (12 mm) (0.5 in; 12 mm (0.47 in)) of error, and averaging measurements over several dozen seconds can improve accuracy to about 8 mm (0.31 in). That level of accuracy rivals first-class GNSS surveying equipment used by the Geospatial Information Authority of Japan, and direct comparisons at the same point have reported differences of only a few millimeters. In other words, LRTK has been confirmed to achieve the centimeter-level precision that previously required equipment costing several million yen.

• Usable anywhere without communication: LRTK supports the centimeter-class positioning augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System “Michibiki.” This means that the communication with a base station or the Internet-based correction information previously required is unnecessary. Even in remote mountainous areas or out-of-coverage locations, LRTK can receive correction data directly from satellites and perform high-precision positioning. It is effective even when mobile networks are down during disasters, and local governments have begun to use LRTK in disaster response.

• Easy operation with no specialized knowledge required: LRTK software, provided as a smartphone app, is designed with an intuitive UI so that it can be used without specialized surveying knowledge. While conventional surveying equipment required skilled operation and setup, LRTK allows users to obtain required coordinates simply by pressing a “Start Positioning” button on the smartphone screen. Management and sharing of positioning data are automated through cloud integration, making it easy for anyone to start high-precision positioning immediately.

• Battery-powered and extensible: Despite its small size, the device’s internal battery supports about 6 hours of continuous positioning, and it also supports power via USB Type-C. It can be used while charging from a commercially available mobile battery, providing confidence during long fieldwork. In addition, mounting it on a monopod or a pole with a tip spike allows more accurate observation of survey points. It can also be attached to an iPad for use on a larger screen, enabling flexible operation according to the application.

• Low cost: One of the biggest advantages is the low introduction cost. The LRTK system is significantly cheaper than conventional surveying equipment; by simplifying dedicated hardware as much as possible and keeping the configuration minimal, costs are reduced. Without expensive equipment, users can still enjoy the benefits of high-precision positioning, making it easier for small sites and budget-limited projects to adopt.

• Multifunctional integrated system: LRTK is not just a device for measuring positions. Through smartphone apps and cloud services, the high-precision position information obtained can be applied to various uses. Examples described later under “What you can do with LRTK” include combining iPhone’s built-in LiDAR scanner to acquire high-precision 3D point cloud data or projecting designs and models into real space using AR—LRTK can handle these as an all-in-one solution.

Note: where the text refers to centimeter-level accuracy, this is described as centimeter-level accuracy (cm level accuracy (half-inch accuracy)).

What you can do with LRTK

By leveraging LRTK’s high-precision positioning capabilities, many tasks that previously required additional equipment or extra effort can now be completed with just a smartphone. Main functions and uses achievable with LRTK and dedicated apps include the following.

• 3D point cloud scanning: Utilizing iPhone LiDAR capabilities, you can scan surrounding structures and terrain in 3D to obtain point cloud data. By combining LRTK’s high-precision GPS information, geospatial coordinates (latitude, longitude, elevation) can be attached to the acquired point cloud, making it easy to create 3D data that directly aligns with surveying or design coordinate systems.

• AR overlay of design data: Preprepared 3D models or drawings can be displayed on-site using AR. Normally, accurate AR alignment requires marker placement or manual adjustments, but by using LRTK’s absolute coordinates, models can be overlaid exactly in the intended location without additional alignment. For stakeout (layout) work, digital drawing coordinates can be visualized in AR to intuitively guide on-site marking of stake positions.

• High-precision photo records: Photos taken with a smartphone camera can be tagged and saved with precise positioning coordinates and azimuth at the time of shooting. This makes it easy to compare photos taken from the same point and angle over time for periodic inspections of structures. Photos with location data are uploaded to the cloud, allowing office-based personnel to accurately grasp on-site conditions.

• Earthwork volume calculations and heatmaps: For embankment and excavation volume calculations in earthworks, LRTK and a smartphone can perform these tasks easily. Volumes can be calculated from point clouds obtained by 3D scanning, and changes can be visualized as color-coded heatmaps to intuitively understand progress and deviations from design. Earthwork management that previously required specialized software and analysis can now be done easily on site.

• Track logs and area measurements: Walking a site with an LRTK-equipped smartphone records a high-precision track log. You can walk the survey area to measure the boundary and then compute area or generate maps directly. Whereas conventional methods required GPS loggers or multiple point measurements by surveyors, LRTK allows a single person to complete area measurements by moving around.

• Indoor positioning: Even inside buildings where GPS signals cannot reach, LRTK can combine sensors with AR technology to enable relative high-precision positioning. For example, if reference points are set inside a building, positions can be recorded within that coordinate system. It is designed to flexibly handle environments where normal GNSS cannot be used, such as underground floors or tunnels.

In addition, LRTK offers features beyond simple GPS reception, such as “object positioning” where targets in inaccessible or hazardous locations are positioned by image processing, and cloud-based sharing and viewing of point cloud and measurement data. LRTK acts as an integrated platform; with a single smartphone and LRTK device, you can cover surveying, measurement, recording, and sharing across a wide range of tasks.

Comparison of LRTK and traditional systems

Here we summarize key comparisons between LRTK, traditional RTK-GNSS equipment, and typical smartphone-integrated GPS.

• Positioning accuracy: Smartphone GPS is low-accuracy with errors around 5–10 m, while both LRTK and traditional high-precision GNSS equipment achieve approximately ±1–2 cm (±0.4–0.8 in) horizontally and about ±3 cm (±1.2 in) vertically. In terms of accuracy, LRTK rivals dedicated equipment and is practically comparable.

• Equipment and portability: Traditional RTK surveying systems require large setups including receivers, tripods or poles, batteries, and controllers. LRTK requires only a smartphone and a palm-sized receiver and is pocketable. While a smartphone alone is the most compact, LRTK offers almost the same level of convenience for positioning tasks.

• Ease of operation: Conventional equipment often requires a skilled surveyor to set up and operate and may require two people for some tasks. LRTK is designed as a smartphone app that anyone can use, enabling one person to perform surveying while moving around a site. Smartphone GPS is convenient but lacks sufficient accuracy for professional use, making LRTK overwhelmingly superior for operational tasks.

• Dependence on communication environment: Traditional RTK relies on radio links with a base station or Internet-based correction services, and positioning can fail if communications are interrupted. LRTK receives augmentation signals directly from Michibiki satellites, allowing positioning in areas without mobile coverage. Smartphone GPS also works without communication but lacks the requisite accuracy for surveying.

• Functional extensibility: Conventional GNSS receivers typically output positioning data only and do not provide point cloud acquisition or AR display functions. Because LRTK is a smartphone-linked system, it supports a wide variety of functional extensions. While smartphone GPS can use many apps, its low accuracy makes it unsuitable for accurate point cloud scanning or surveying.

• Introduction cost: High-performance GNSS surveying equipment is very expensive and imposes a large initial burden. LRTK can be introduced at a dramatically lower cost and reduces maintenance expenses. It also does not require statutory inspections or calibrations for equipment, lowering operational costs. Smartphone GPS requires no additional cost beyond owning the device, but its accuracy is insufficient for professional use and thus is not a viable comparison.

As shown above, LRTK maintains the accuracy and reliability of traditional RTK-GPS equipment while dramatically improving portability, ease of use, and cost. It has reached a level where it can be sufficiently utilized in sites that require high-precision positioning without relying on specialized equipment.

Use cases for LRTK

The capabilities of LRTK have already been demonstrated in various field applications. Here are some examples.

• Surveying and stakeout at construction sites: Traditionally, construction surveying used total stations (optical surveying instruments) or expensive GNSS surveying equipment with two or more people marking stakeout positions. After introducing LRTK, a single person can walk the site with a smartphone and view stake positions in AR to intuitively identify points. This enables efficient and accurate stakeout work even at sites facing labor shortages.

• Disaster response and infrastructure inspection: In situations where it is difficult to bring conventional surveying equipment—such as landslide sites caused by heavy rain or earthquakes—LRTK allows lightweight teams to visit sites and conduct immediate surveying. For example, a municipal government (Fukui City) adopted an iPhone and LRTK-based surveying system for disaster recovery to assess damaged sites and manage repair progress. Because positioning can be performed using satellite augmentation signals even when mobile networks are down, LRTK is expected to be a valuable tool for initial emergency responses.

• Forest surveys and environmental monitoring: In forests and mountainous areas, satellite signal reception is often unstable due to tree cover, and even high-performance GNSS can have large errors. However, LRTK has been reported to achieve high-precision positioning in environments where typical GPS devices produced meter-level errors. With multi-band GNSS support and advanced filtering techniques, LRTK can maintain cm-level positioning even under tree cover. This expands its use for plot surveys in forests and recording locations for environmental sensors.

• Infrastructure maintenance and management: LRTK is also being applied to bridge and road maintenance. For example, in bridge pier monitoring, periodic coordinate-tagged photos taken with LRTK allow detection of displacements or anomalies at the centimeter scale over time. Traditionally, visual inspections and tape measurements were the norm, but adding high-precision positional data improves diagnostic accuracy and efficiency.

These cases show that LRTK embodies the concept of “simple surveying” across a wide range of scenes beyond construction and surveying, including disaster response and environmental fields. Being a high-precision yet easy-to-use tool is accelerating digital transformation (DX) on job sites.

Summary

When comparing RTK GPS solutions, LRTK is truly an innovative solution that delivers “high precision made easy.” LRTK secures accuracy comparable to conventional RTK positioning equipment while achieving dramatic improvements in portability, cost, and ease of use, and is likely to be adopted increasingly across sites.

For those who need high-precision positioning but could not afford traditional equipment, or those seeking to improve operational efficiency with the latest surveying technology, LRTK is a compelling option. Step into the world of simple surveying with just a smartphone and enjoy unprecedented speed and accuracy in position measurement. Why not experience the capabilities of the next-generation positioning system, LRTK?

FAQ

Q. What does RTK GPS stand for? How is it different from ordinary GPS? A. RTK stands for “Real Time Kinematic,” and it is also called real-time differential positioning. Ordinary GPS positioning receives satellite signals alone and can have errors of several meters, but RTK uses correction information from a base station to reduce errors to a few centimeters. RTK GPS is therefore a GPS technology that achieves markedly higher precision through corrections.

Q. What do I need to use LRTK? A. Basically, you need a smartphone such as an iPhone, an LRTK dedicated GNSS receiving device, and the LRTK app. Attach the device to the iPhone and launch the app to perform high-precision positioning on site. Positioning data can also be integrated with cloud services and viewed or downloaded from a PC.

Q. How accurate is LRTK? Is it comparable to high-end surveying equipment? A. LRTK achieves centimeter-level accuracy (cm level accuracy (half-inch accuracy)), with horizontal accuracy of about 1–2 cm (0.4–0.8 in) and vertical accuracy within about 3 cm (1.2 in). This accuracy is comparable to high-performance GNSS equipment used for first-class geodetic surveys. In field comparisons at the same point, differences between LRTK and first-class GNSS receivers have been on the order of a few millimeters. Therefore, in terms of positioning accuracy, LRTK is comparable to traditional professional equipment.

Q. Does positioning require a communication environment? Can it be used in remote mountains or disaster sites? A. LRTK can be used where smartphone communication is unavailable. It can receive the CLAS augmentation signal distributed from Japan’s Quasi-Zenith Satellite “Michibiki” directly and use it for corrections, so high-precision positioning is possible in mountainous areas or disaster sites where mobile networks are unavailable. However, since it requires reception of satellite signals, fully obstructed indoor or tunnel environments require separate measures (such as indoor positioning mode).

Q. How long does the LRTK battery last? A. The LRTK device itself operates on its internal battery for about 6 hours. For long operations, it is possible to use USB-C power from a mobile battery while operating. The system is designed so fieldwork can be continued for more than half a day, including the smartphone.

Q. Can anyone use LRTK? Do I need a surveyor’s license or special training? A. LRTK is operable via an intuitive smartphone app, so basic positioning and measurement can be performed without specialized surveying qualifications or advanced training. Of course, surveying knowledge expands the range of applications, but operation is not as difficult as with conventional equipment that requires experienced operators. Also, LRTK is not considered “fundamental surveying” under the Survey Act for which special device certification is required (although it achieves first-class-equivalent accuracy, it has not obtained official first-class device certification to keep costs low). Therefore, for general field surveying and construction management, anyone can adopt and use LRTK with ease.