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Compact and Lightweight RTK Surveying GPS Device with Fast FIX

This article takes an average of 2 minutes and 30 seconds to read

Published March 14, 2025

In construction surveying and civil engineering, "positioning" technology that accurately measures location is indispensable. Among these, Real-Time Kinematic (RTK) positioning has seen a significant increase in importance in recent years, as it provides high precision with an error margin of just a few centimeters and immediate positioning information.

With advancements in technology, the cost of RTK surveying equipment has decreased, providing a boost to the promotion of DX (Digital Transformation) in the construction industry and supporting the i-Construction initiative.

On the other hand, traditional surveying methods had several challenges. For example, total station (TS) surveying is known for its millimeter-level precision but involves large equipment that is cumbersome to set up, and the positioning speed is limited as angles and distances need to be measured for each point. Additionally, GPS-only positioning tends to have errors of several meters, resulting in insufficient accuracy. Traditional GNSS surveying equipment (RTK-compatible receivers) was also expensive, heavy, and time-consuming for initial setup and fixing the position (FIX).

To address these challenges, compact and lightweight RTK surveying GPS devices that enable fast FIX (instant positioning) have emerged. With the latest RTK-GNSS receiver technology, some devices now feature a "Fast FIX" function, allowing for centimeter-level accuracy to be established in just a few seconds after powering on. Moreover, with their compact size and lightweight design, these devices dramatically reduce the burden of carrying and setting them up on-site. In this article, we will explain the mechanism and benefits of this innovative RTK surveying device that can be described as "a must-know!"

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RTK Surveying GPS Device Technology and Mechanism

RTK (Real-Time Kinematic) positioning is a positioning method where the base station (fixed station) and the moving station (rover) simultaneously receive signals from multiple satellites, and the position of the moving station is calculated in real-time based on the known position of the base station. By analyzing the correction information sent from the base station, the moving station’s receiver can reduce errors from about 2 meters in standalone GPS positioning to just a few centimeters. In this way, RTK is a type of relative positioning, achieving high accuracy by compensating for error factors.

RTK surveying GPS devices condense this RTK technology into compact devices, while also enabling "Fast FIX." As the name suggests, Fast FIX is a technology that allows for the instant initialization of positioning (obtaining the FIX solution). Traditional RTK receivers often required tens of seconds to minutes to obtain the FIX solution after satellite capture. However, the latest devices, with multi-band (L1/L2/L5, etc.) and multi-GNSS (supporting GPS, GLONASS, Galileo, Michibiki, etc.), have significantly improved the positioning environment, enabling the acquisition of the FIX solution within a few seconds.

For example, high-performance RTK receivers from overseas have reported achieving "centimeter-level accuracy in 5 seconds." With Fast FIX, continuous positioning while moving and instant point observations can be conducted smoothly, directly contributing to faster surveying operations.

Additionally, the compact and lightweight design is another significant technical advantage. Previously, large antennas and high-output batteries were required for high precision, but thanks to the increased integration of circuit boards and power-saving technologies, devices have been successfully miniaturized.

Specifically, through innovations like making the circuit boards thinner and designing an integrated antenna-battery structure, a device that can be integrated with a smartphone has been achieved. The miniaturization makes it easier to bring equipment to the site and significantly reduces the burden on surveyors when moving or setting up. Since surveying often involves working in difficult locations such as uneven terrain or high places, lightweight equipment provides significant benefits in both safety and work efficiency.

In summary, the latest RTK surveying GPS devices combine "high-precision positioning via RTK," "instant positioning via Fast FIX," and "portability via compact and lightweight design," making them a bundle of advanced technology. In the next chapter, we will look at the specific benefits these technologies bring to actual surveying tasks.

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Benefits of Introducing Compact and Lightweight RTK Surveying GPS Devices

By introducing compact and lightweight RTK surveying GPS devices, the following benefits emerge for on-site surveying tasks:

• Increased Surveying Speed: The Fast FIX function eliminates almost all waiting time for positioning initialization. With this feature, even immediately after powering on the moving station or resuming positioning, centimeter-level accuracy is achieved instantly, reducing the time spent on measurements at each point. For example, tasks that previously required waiting for several tens of seconds at each point can now be completed instantly by simply moving and pressing a button. As a result, the number of points that can be surveyed in a day increases significantly, leading to an overall reduction in project timelines.

• Improved Accuracy and Work Efficiency: Since the positioning accuracy with RTK itself is high, more precise data can be collected compared to traditional methods. With accuracy within a few centimeters, immediate positioning allows for the elimination of setup steps like benchmarks or the streamlining of as-built management, reducing rework in subsequent stages. Some products display and share surveying results in real-time on tablets or in the cloud, allowing for immediate data verification and instruction issuance on-site, thereby improving team-wide work efficiency. The small errors in positioning also reduce the need for re-measurements or additional surveying, striking a balance between quality assurance and efficiency.

• Cost Reduction and Workforce Optimization: The introduction of compact RTK devices offers economic benefits as well. First, there is a significant effect on workforce reduction, as surveying tasks that previously required a team of two can now be completed by one person, leading to savings in labor costs. In fact, reports indicate that using RTK positioning has led to "significant reductions in personnel and effort" compared to total station surveying. Additionally, the cost of the devices themselves has decreased in recent years, with affordable RTK-GNSS receivers now available. Products like the ultra-compact RTK device "LRTK Phone" are praised for being "extremely affordable," making it possible to minimize initial investment costs. As a result, even with limited budgets or manpower, high-precision surveying can be achieved, improving overall cost performance.

Thanks to these benefits, the introduction of compact RTK surveying devices is expected to have a significant impact on a wide range of sites, from large general contractors to small and medium-sized civil contractors, surveying companies, and infrastructure inspection service providers. The latest technology, which combines "faster work," "higher accuracy," and "reduced labor," can truly be called a revolution in on-site productivity.

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Comparison with Traditional Surveying Methods

Now, let's specifically compare this compact and lightweight RTK surveying GPS device with two representative traditional surveying methods: total station surveying and RTK surveying using GNSS devices. We will examine the features and differences of each method.

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A total station measures angles and distances by optically targeting the object, requiring a clear line of sight and a minimum of two people: an operator and a target holder. While it offers high precision, there are efficiency challenges when surveying large areas, as repositioning and additional personnel are required.

Workers measure positions using a GNSS antenna at the end of a pole and a controller in hand. In traditional RTK-GNSS surveying, the rover antenna (moving station) and data receiver are carried, and a separate base station is required to provide correction data via radio or network. GNSS surveying does not require line of sight, allowing one person to survey a large area. However, the equipment, including the antenna, battery, and communication devices, tends to be relatively large, and initial satellite acquisition and FIX solution can sometimes take time.

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Introduction to LRTK Products

Here, we will briefly introduce the LRTK series, which stands out among the many compact RTK surveying GPS devices.

The key feature is its pocket-sized device that integrates with a smartphone. Among them, the "LRTK Phone" is a unique product that attaches a dedicated receiver to an iPhone or iPad. With an ultra-compact body weighing just 125g and 13mm in thickness, it also includes a built-in battery. By simply attaching this device to a smartphone, your phone instantly transforms into an all-in-one surveying tool with centimeter-level accuracy.

The device is designed for easy attachment and detachment from the dedicated smartphone cover with just one touch, making it incredibly convenient to pull it out and start surveying whenever needed. It was developed with the goal of being a "one device per person" tool for the field, allowing you to carry it in your pocket at all times and use it instantly when needed.

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By installing the dedicated app "LRTK" on the smartphone and connecting via Bluetooth, the device can receive satellite correction data and control positioning. The integration with the smartphone eliminates the need for cables, making it highly portable and easy to handle on-site. Additionally, the device can be detached from the smartphone and mounted on a monopod or tripod to perform fixed-point positioning while remaining wirelessly connected to the smartphone. This flexibility allows it to be used adaptively according to on-site conditions.

In terms of accuracy, the LRTK supports network-based RTK (base station data via Ntrip), allowing for horizontal accuracy of ±2 cm and vertical accuracy of approximately ±3 cm by utilizing commercial VRS services and public reference point information. Furthermore, to enable use in areas with no mobile signal, such as mountainous regions, there are models that support CLAS (Centimeter-level Augmentation Service) provided by Japan's quasi-zenith satellite system, Michibiki. This allows for high-precision positioning even in areas where satellite signals from base stations were previously unavailable, such as in mountainous areas or near tunnel entrances, by receiving direct high-precision augmentation signals from satellites. This significantly expands the "usable range" on-site.

One of the differentiating factors of the LRTK compared to competing products is its integration with cloud services and AR features. The LRTK can instantly plot the acquired positioning data and trajectories on a map in the cloud, allowing for immediate sharing within the team. Additionally, it easily tags photos taken with the smartphone camera with high-precision location coordinates and orientation data, which can be managed on a map using the dedicated app. This enables significant efficiency improvements in tasks that traditionally required separate equipment or manual calculations, such as accurately recording inspection locations in infrastructure maintenance or directly importing point clouds into CAD for volume calculations.

Furthermore, an AR (Augmented Reality) construction simulation function is also available, enabling advanced use cases such as overlaying design drawings or as-built data on the site visuals for verification. These features, unique to smartphone integration, provide a platform that supports the DX of the entire workflow, going beyond just a surveying tool.