Cloud-Connected Survey Data Sharing! Network RTK as the Information Source Linking Field and Design

Table of Contents

• What is Network RTK?

• Benefits Network RTK Brings to the Field

• Survey Data Sharing Expanded by Cloud Integration

• New Workflow That Connects Field and Design

• Conclusion

• FAQ

What is Network RTK?

In recent years, improving productivity on surveying sites using cloud and GNSS technologies has become a major theme. This article focuses on "network RTK," the key to enabling survey data sharing via cloud connectivity, and explains its mechanism and effects.

In construction and surveying work, results can be greatly affected even if positions are off by a few centimeters (a few in). In highway and railway infrastructure development, pile driving and as-built control in civil engineering, even small positioning errors can influence quality and safety. For that reason, RTK (Real-Time Kinematic) technology, which corrects satellite positioning errors in real time to obtain high-precision positions, is important.

Standalone positioning using ordinary GNSS (GPS) can produce errors on the order of meters. However, by using RTK, correction information from a reference station can be applied in real time, enabling immediate positioning with centimeter-level accuracy (half-inch accuracy). Achieving high-precision real-time positioning greatly contributes to improving field work efficiency and reducing labor in surveying tasks. This technology is also indispensable as the foundation of the recently promoted i-Construction (ICT construction).

RTK positioning is a relative positioning method using two GNSS receivers: a reference station (fixed) and a rover (mobile). A reference station is installed at a point where accurate coordinates are known in advance, and the station calculates positioning errors from the difference between the signals received from satellites and its own position. The correction data is sent in real time to the rover via radio or other means, and the rover applies the correction to the satellite signals it receives to determine highly accurate coordinates.

The accuracy obtained by RTK is greatly affected by the distance between the reference station and the rover (baseline length). If they are close, delay errors due to the ionosphere and troposphere are largely common and cancel out, but as distance increases, uncorrectable errors grow. Therefore, traditionally it was common to place the reference station within a few km of the work area and transmit correction information using low-power radios while positioning. With proper operation, horizontal accuracy on the order of 1–2 cm (0.4–0.8 in) can be obtained, making positioning vastly more precise compared to conventional GPS positioning, which was on the meter scale.

The constraint of RTK that required installing a reference station on site each time was resolved by network RTK. This system uses a network of many reference stations (continuously operating reference stations) distributed nationwide to generate correction data as if a virtual reference station were placed near the user. A representative method, VRS (Virtual Reference Station), works by the user device (rover) sending its approximate position to a server, which integrates and analyzes observation data from multiple surrounding reference stations and generates correction information assuming a "virtual reference station" exists near the user.

The correction data for the generated virtual reference station is delivered to the rover on site via the Internet (mainly using Ntrip). Because the rover can perform RTK positioning as if a reference station were "right next to it," high-precision positioning over a much wider area becomes far easier than before.

With the advent of network RTK, users no longer need to provide their own reference stations on site, and surveying can be completed with a single receiver (rover). Time and effort spent on preparations are greatly reduced, improving work efficiency. Also, because a virtual reference station is always set near the positioning point, accuracy degradation due to baseline length hardly occurs, and uniform high accuracy can be maintained even when the field covers a wide area.

In Japan, the Geospatial Information Authority has established about 1,300 electronic reference stations nationwide and built a system (GNSS Continuously Operating Reference Stations) that provides correction information in real time. By using this, absolute coordinates in the Japan Geodetic Datum 2011 (World Geodetic System) can be acquired in real time without placing a reference station on site. Additionally, private companies’ network RTK services using mobile communication networks have become widespread, with major carriers deploying their own networks of reference stations numbering in the thousands. As long as you are within a communication area, it has become possible to obtain stable centimeter-level position information anywhere in Japan.

Recently, methods that receive correction information directly from satellites have also appeared, in addition to systems that use ground reference station networks. An example is the centimeter-level positioning augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System, Michibiki. With a compatible receiver, centimeter-level positioning is possible in real time without using the Internet. (A benefit is that receiving augmentation signals from the satellite is free of charge.) This makes high-precision positioning possible even in mountainous areas outside mobile coverage, and its use is expected to expand further.

Thus, the spread of network RTK has brought great benefits to surveying sites. Next, let us look at the concrete advantages.

Benefits Network RTK Brings to the Field

Now that you understand how network RTK works, let’s see what benefits it actually brings to surveying operations in the field. Compared with traditional methods, introducing network RTK offers the following advantages.

• No need to install a reference station: There is no need to set up your own reference equipment on site, reducing the burden of transporting equipment. Costs for acquiring multiple expensive base stations are also reduced, and tasks can be completed with a single receiver.

• Greatly reduced preparation time: Because you do not need to install a reference station or set up known points, positioning on site can begin immediately. Pre-work such as traverse surveying and establishing control points is significantly reduced, allowing limited work time to be used effectively.

• Stable high-precision positioning: Centimeter-level accuracy (half-inch accuracy) can be obtained uniformly even across wide sites. There is no worry about accuracy dropping due to distance from a reference station, making it easier to manage positioning quality.

• Work with fewer personnel: Because positioning can be performed with just one receiver and a communication environment, assistants or base station operators that were previously required become unnecessary. More surveying tasks can be handled by one person, helping address labor shortages.

• Improved consistency with design data: Network RTK can directly obtain absolute coordinates based on the World Geodetic System, reducing discrepancies with the coordinate system used in design drawings. Measured point coordinates can be plotted directly on drawings, reducing errors associated with coordinate transformations or adjustments to local coordinate systems.

• Affinity with ICT technologies: The high-precision positioning information obtained by network RTK can be integrated with advanced ICT technologies such as drone photogrammetry, machine guidance for construction equipment, and AR-based site visualization. When combined with real-time sharing of survey data, it becomes a powerful foundation for driving DX (digital transformation) at the site.

Survey Data Sharing Expanded by Cloud Integration

Once network RTK dramatically improves field positioning accuracy and efficiency, the next key point is how to utilize and share that survey data. This is where cloud integration demonstrates its power. By connecting positioning devices to the Internet and storing and sharing acquired data in the cloud, information exchange between the field and the office (designers) becomes dramatically smoother.

Traditionally, surveyors would bring data from the field back to the office on USB drives or in handwritten notebooks, organize it there, and then hand it to designers. This process caused time lags before survey results were reflected in designs and created risks of transcription errors. Introducing cloud-based data sharing allows you to share accurate survey data instantly without physical handoffs.

Main benefits of cloud integration:

• Immediate information sharing between field and office: Coordinates of observed points and photos collected on site can be uploaded to the cloud on the spot, and office-based designers can check the latest data immediately. The wait time for survey results is reduced, and design or review can be reflected within the same day.

• Prevention of transcription errors: Because data is shared automatically without going through handwritten notes or spreadsheet entry, human transcription errors are eliminated. Everyone can share a single latest version of the data, removing confusion about which file is current.

• Simultaneous use by multiple stakeholders: Cloud-hosted survey data can be accessed not only by field staff but also by designers and project managers. With everyone looking at the same information during discussions and decisions, communication loss is reduced and team productivity increases.

• Faster feedback: With bidirectional connections between field and design via the cloud, designers can easily request additional measurements or issue drawing revisions during surveying. If an unexpected issue arises on site, the situation can be shared immediately with photos and notes, allowing design changes to be considered right away.

• Secure data storage: When data is stored in the cloud, information is not lost even if a device is lost or damaged. Centralized management including past surveying history makes it easy to review "when and where what was measured" later.

In this way, cloud integration significantly expands the ways survey data can be used and contributes to optimizing the entire workflow.

New Workflow That Connects Field and Design

Combining network RTK with the cloud creates a new workflow that seamlessly connects the field and design. Here is one example presented step by step.

• Field surveying: The surveyor measures site points using a GNSS receiver compatible with network RTK. There is no need to set up control points or wait for post-processing as before; centimeter-level coordinates (half-inch accuracy) can be obtained on the spot.

• Send data to the cloud: Measured position data and ancillary information such as comments are uploaded to the cloud immediately from the site. With one button the data is saved to the server and automatically shared with stakeholders.

• Office data review: Designers in the office check the uploaded latest data on a PC. Measured points are plotted on maps, and photos, if any, are linked to their positions so the site situation can be grasped in real time.

• Feedback from design: As needed, designers communicate additional points to be measured or design changes to the field via the cloud. This is efficient because instructions can be issued through shared cloud information without using phone calls or email.

• Field response and additional measurement: The surveyor carries out additional measurements or layout work based on the design instructions on site. New measurement results are similarly shared to the cloud, and designers can make immediate judgments while viewing them.

• Integration of deliverables: Ultimately, all survey data is consolidated in the cloud. By the time the field team returns to the office, work on reflecting data into design drawings or creating as-built drawings can already be underway, eliminating waiting time for data handoffs.

As described above, using network RTK and the cloud makes data exchange between field and design that used to take several days almost real time, leading to major time savings and reduced rework. Because high-precision survey data collected on site can be reflected in design immediately, discrepancies in later processes are minimized, contributing to higher-quality deliverables.

Conclusion

Network RTK and cloud-based data sharing are poised to greatly change surveying practices. Accurate positioning information obtained in the field can be delivered to designers instantly, and design feedback can be received on the spot. Field and design, which previously operated separately, are now synchronized in real time, reducing wasted waiting time and rework and improving the overall speed and quality of projects.

A solution attracting attention as an easy way to realize this advanced surveying workflow is LRTK. By combining a smartphone with a compact high-precision GNSS receiver, LRTK enables even untrained personnel to perform centimeter-level surveying by themselves. It also offers a variety of functions such as photo capture, point cloud scanning, and AR surveying, allowing comprehensive digitalization of site conditions with a single device. Positioning data and site photos can be uploaded on the spot to the cloud (LRTK Cloud) and instantly shared with the office team. LRTK can be seen as a tool that materializes the "cloud-connected survey data sharing" introduced in this article. Please pay attention to the use of LRTK, which supports smart surveying by maximizing the benefits of network RTK and cloud utilization. The use of network RTK to connect field and design in real time will likely become the trump card for operational improvement at even more sites going forward.

FAQ

Q: What is network RTK? A: Network RTK is a technology that receives correction information provided by multiple reference stations via the Internet to perform high-precision positioning. Unlike traditional RTK, there is no need to install your own reference station on site; via a communication line you can obtain centimeter-level correction data from surrounding reference station networks.

Q: What is needed to use network RTK? A: You need an RTK-capable GNSS receiver and a communication environment to obtain correction information. Specifically, this means a receiver that can connect via mobile communication networks and a subscription to a correction data distribution service (or use of public augmentation signals). For example in Japan, you can use paid correction services over mobile networks or the Michibiki centimeter-level augmentation service (CLAS). In either case, with compatible equipment and a communication environment, real-time high-precision positioning on site is possible.

Q: What are the benefits of sharing survey data via the cloud? A: The cloud allows field survey data to be shared with the office immediately, greatly reducing time loss. There is no need to bring data back on USB, preventing transcription errors, and multiple people can access the latest data simultaneously for smooth collaboration. Also, because data is stored in the cloud, information is not lost if a device fails, and past surveying history can be safely managed.

Q: Can a smartphone really achieve centimeter-level surveying? A: It is possible if you connect a dedicated high-precision GNSS receiver to a smartphone or tablet. The smartphone alone does not have high positioning accuracy, but by combining a high-precision antenna/receiver and using network RTK corrections, you can achieve accuracy comparable to dedicated surveying instruments. For example, LRTK uses an integrated RTK receiver with a smartphone to enable anyone to easily achieve cm-level positioning.

Q: Can non-specialist users operate it? A: Yes. Recent network RTK-compatible devices and apps are designed to be user-friendly, and many allow intuitive surveying operations. Tools like LRTK that offer one-touch positioning and cloud sharing enable non-experts to perform field surveys, allowing sites to advance DX (digital transformation) without extensive training costs.

Q: What degree of positioning accuracy does network RTK provide? A: When used properly, horizontal positioning is typically within about ±1–2 cm (±0.4–0.8 in), and vertical errors are on the order of a few centimeters (a few in). This is vastly more accurate than standalone positioning (meter-level errors), but accuracy can degrade in environments with surrounding obstructions or poor radio conditions. Weather and satellite geometry also affect the stability of positioning, so for critical surveys it is advisable to allow margins and perform multiple checks. Even so, network RTK offers dramatically higher precision compared to traditional positioning and is a reliable solution for most surveying tasks.