Challenges and Solutions for RTK Operation on Overseas Projects

In overseas construction and surveying projects, RTK (Real-Time Kinematic) positioning is a critical technology that affects construction accuracy and efficiency. In Japan, Continuously Operating Reference Station (CORS) networks and network RTK services using the VRS method are well established, making stable centimeter-level positioning relatively easy to use. However, at overseas sites the communication infrastructure is often less developed and more unstable than in Japan, and attempting to operate RTK in the same way frequently encounters various obstacles. This article explains in detail the common challenges faced when using RTK positioning on overseas projects and the solutions to those challenges. Focusing on ways to cope with communication constraints, it comprehensively covers points for setting up base stations, alternative technologies, equipment selection, and emerging positioning solutions.

RTK Operational Challenges Caused by Underdeveloped Communication Infrastructure

In rural areas or emerging countries abroad, underdeveloped or unstable communication environments can be a major obstacle to RTK operation. Specific challenges include the following points.

• Regions where network RTK (VRS) is not available: In Japan, VRS (Virtual Reference Station) correction services allow RTK positioning without setting up your own base station. However, overseas some countries do not have a nationwide GNSS reference station network, and public or commercial VRS correction services may not be available in many areas. Therefore, to use RTK on-site you may have no choice but to set up your own base station.

• Difficulty in setting up and operating base stations: If you provide your own base station, securing reference-point coordinates is the first challenge. Without reliable known coordinates, high-accuracy positioning is difficult. In addition, finding a location to install the GNSS receiver for the base station and transporting and installing the equipment are labor-intensive. If the site is in a remote area far from urban centers, you must consider securing power for stable base station operation (long-term operation may require external batteries or solar panels), theft prevention measures, and equipment management by local staff. Also, as positioning accuracy decreases when the distance between the base and rover increases, for wide-area surveys you need to consider appropriate placement or multiple installations.

• Constraints on local radio communications: When a base station is installed, a communication method is required to transmit RTK correction information to the rover. Common options are low-power radio in the UHF band or digital simple radios, or Ntrip distribution over the internet via cellular networks. However, radio use laws and regulations differ by country, and radio equipment or frequency bands used in Japan may not be usable overseas as-is. For example, in some countries licensing or permits may be required for RTK radio transmission, or available frequency bands may be limited. Even if radio use is permitted, range is limited and terrain or obstacles can make communications unstable. If radio communication is difficult locally, you must send correction data over the internet, but that is impossible if cellular service is out of coverage.

• Data usage and line-quality issues: Even if mobile data (cellular network) is available locally, there are issues with communication quality and cost. RTK requires sending correction data in real time every second, so an stable, low-latency data link is required. In mountainous areas or infrastructure-poor regions of developing countries, communication speeds may be slow or signals may be intermittent, causing RTK to lose its fixed solution. If solutions frequently float or are lost, surveying work is severely affected. Also, when using international roaming or local SIMs, data plans may have usage limits or caps, so long RTK operations risk increased costs or throttling.

As described above, overseas the underdevelopment and instability of communication infrastructure often make it difficult to meet the RTK prerequisite of “delivering correction information in real time,” and methods that work domestically do not always apply.

Alternative Technologies to Reduce Communication Dependence

To perform high-precision positioning in areas with poor communication, it is effective to use technologies and practices that reduce dependence on real-time communications. Useful positioning solutions for overseas sites that require little or no communication include the following methods.

• Use of SBAS (Satellite-Based Augmentation Systems): SBAS provides wide-area positioning correction signals from geostationary satellites. Representative systems include WAAS in North America, EGNOS in Europe, and MSAS via Japan’s QZSS. Receiving SBAS signals can significantly reduce errors compared with standalone positioning, improving accuracy from several meters to under 1 m (3.3 ft). While SBAS cannot reach the centimeter-level accuracy of RTK, it is a free, satellite-delivered source of correction information useful in environments with no communication infrastructure. SBAS can substitute for preliminary surveys or coarse machine guidance where very high accuracy is not required.

• Use of CLAS via quasi-zenith satellites: Japan’s Quasi-Zenith Satellite System (QZSS) “Michibiki” provides a centimeter-class correction service (CLAS). CLAS is primarily a service for Japan, but Michibiki’s augmentation signals can be received in parts of Asia and Oceania in some cases【※】. Using a CLAS-capable GNSS receiver allows receiving centimeter-level correction information directly from satellites without relying on terrestrial internet or radio, enabling high-accuracy positioning. For example, Japanese construction firms conducting surveys in Southeast Asia—where local base station networks are sparse and communication networks are weak—have used Michibiki’s high-precision augmentation signals (CLAS and experimental MADOCA) for accuracy verification. Achieving RTK-equivalent accuracy from CLAS alone requires receiver support and sufficient processing time, but it is at least a very reliable option for positioning outside communication coverage.

• Use of PPK (Post-Processed Kinematic): If real-time results are not required, high-accuracy post-processing (PPK) is also effective. In PPK, raw GNSS data observed by the rover are recorded and later combined with base station data for correction processing to obtain high-accuracy solutions. Because no real-time communication is needed on-site, full-accuracy results can be obtained even when correction data cannot be transmitted in real time. For example, processing data in the office after a day’s surveying can yield centimeter-level positioning equivalent to real-time RTK. The drawback is that coordinates are not available immediately on-site, so PPK cannot be used for tasks requiring instant staking out or machine control, but for geodetic control or as-built verification—tasks that do not require real-time results—PPK is fully applicable. Since the base station only needs to record data, logging for PPK can serve as a backup if communications are unstable.

*(※Note: CLAS is a service aimed at the region around Japan and its reception range is limited. In overseas application areas, differences in ionospheric models and other factors mean accuracy and availability are not guaranteed to the same degree as within Japan.)*

Preparations and Measures to Ensure Reliable RTK Operation Overseas

Considering the above alternatives, careful planning and countermeasures are essential when operating RTK positioning on overseas projects. The main preparatory items and measures to facilitate RTK operation on-site are summarized below.

• Check local communication conditions and regulations: During project preparation, investigate local communication infrastructure. Identify cellular network coverage, availability of internet lines, and usable frequency bands in advance. Also confirm local regulations regarding the import and use of RTK radio equipment. Some countries require licenses for radio transmitters or impose limits on output power and bandwidth. If necessary, apply for permits from local communications authorities or procure legally usable radio modems. It is prudent to prepare multiple communication options (e.g., internet via local SIM + radio equipment with approved permits).

• Prepare base stations and communication methods in advance: Where VRS is not available, plan to operate your own base station. If bringing high-precision GNSS receivers from Japan, check in advance whether frequency settings need to be changed for local operation (e.g., when radio modems are built-in). Bring tripods, poles, and power equipment that may be difficult to procure locally. Securing reference-point coordinates is also important. If no known survey control points are nearby, establish base station coordinates by long static observations and post-processing (e.g., PPP analysis), or consider asking local surveyors to establish known points. For communications, test radio range between base and rover or verify Ntrip server settings before arriving on site when using internet. Consider satellite phones or offline operation, and prepare backup measures that allow surveying to continue if communications are lost (e.g., PPK operations or handheld GPS positioning).

• Equipment selection and configuration for GNSS: For overseas use, choose GNSS receivers and antennas that are multi-GNSS and multi-frequency capable. Devices that can track not only GPS but GLONASS, Galileo, BeiDou, and others will more easily maintain satellite availability in environments with partial signal blockage. Receivers supporting L1/L2 plus newer bands such as L5 or L6 can receive SBAS or CLAS augmentation signals. Investing in equipment that supports these latest technologies is worthwhile for future operational flexibility. Also confirm that receivers have functions for transforming to local datums and coordinate outputs (since geodetic datums and coordinate systems vary by country). Before deployment, update firmware and verify settings, and ensure you have necessary accessories (survey poles, bubble levels, cables, spare batteries, etc.).

• Operational structure and skill development: Alongside technical preparation, building a team capable of RTK operation on-site is crucial. Survey engineers dispatched from Japan must not only be familiar with the equipment but also able to adapt to local communication environments and languages. Conduct pre-deployment simulation training so they can perform base station setup and troubleshooting. Where possible, train local hires or partner technicians in RTK basics so they can serve as support. Also establish cloud-based data sharing and remote support so daily survey results can be shared with the head office in Japan for quality control and technical assistance; this prevents overseas teams from being isolated. Implement regular inspections and follow-up, and build a team structure that can quickly identify causes and implement countermeasures when problems occur.

With the above preparations and measures, you can operate RTK positioning as stably as possible at overseas sites even when communication infrastructure is not ideal. In other words, “if you cannot do it the same way as in Japan, compensate with the appropriate amount of effort and creativity.”

Simplified LRTK Surveying Using Smartphones + Compact GNSS Receivers

Finally, as a recent new solution, we introduce RTK positioning combining smartphones and compact GNSS receivers. This concept, called “LRTK” developed by a Japanese startup, uses palm-sized RTK GNSS receivers that attach to smartphones, enabling anyone to perform centimeter-level surveying easily. By combining the smartphone’s communication and processing capabilities with the external GNSS receiver’s high-precision positioning, this approach is attracting attention as a practical solution that lowers barriers at overseas sites. LRTK-like solutions offer the following advantages for overcoming common overseas challenges.

• Mobility and ease of use: The smartphone + small receiver setup is extremely compact and lightweight. There is no need to carry dedicated survey equipment; attaching the receiver to a smartphone completes setup. One-handed point observations while moving are feasible, greatly reducing time and effort for equipment setup. High portability is advantageous for large sites or surveys that move between many points.

• Flexible response to communication environments: Small receivers can obtain high-precision correction information independently, reducing dependency on communications. For example, some LRTK terminals for Japan can directly receive Michibiki’s CLAS signals, providing centimeter-level accuracy even outside cellular coverage. In areas where cellular networks are available, the system can switch to network RTK using the smartphone’s connection, so it supports both offline and online operation depending on conditions.

• Lower-cost proliferation: Compared to traditional RTK equipment, LRTK systems leveraging smartphones tend to be less expensive to introduce. As high-precision GNSS receivers become smaller and cheaper, equipping “one person, one device” becomes financially feasible, allowing field staff to measure whenever needed. For overseas deployment where bringing many pieces of equipment is difficult, smartphone + pocket-sized receivers make it practical to supply devices for multiple staff.

• Data utilization and DX benefits: Smartphone integration enables immediate uploading and sharing of high-precision position data to the cloud. Sharing positioning data, photos, and notes with the head office in Japan helps monitor and direct distant sites in real time. Smartphone apps can also implement features such as augmented reality (AR) guidance and verification based on acquired data, enabling simplified tasks like point staking and layout that formerly required specialized equipment. These digital transformation (DX) effects can dramatically improve quality and efficiency of overseas site management and construction control.

Thus, smartphone-based LRTK surveying can be a new solution to RTK operation problems caused by communication infrastructure at overseas sites. In Japan, examples have been reported where LRTK devices proved effective at mountainous construction sites and in disaster response where there was no cellular coverage. Overseas, as compatible satellite services become available, the same approach may enable communication-independent positioning. Most importantly, using smartphones—devices familiar to field technicians—as the platform promotes democratization of the technology, allowing even non-experts to perform high-accuracy surveying.

Conclusion

RTK operation on overseas projects involves various challenges different from domestic work in Japan. The greatest hurdle—underdeveloped communication infrastructure—can be overcome through careful preparation and by leveraging alternative technologies. By combining base station setup and radio communication measures with less communication-dependent methods such as SBAS, CLAS, and PPK, stable high-precision positioning can gradually be achieved even in regions with limited communications. Moreover, next-generation solutions like smartphone + compact GNSS receivers (LRTK) have the potential to significantly change how RTK positioning is conducted overseas. If low-cost, flexible RTK operation becomes possible, surveying and construction quality at overseas sites—where accuracy was previously compromised—can be improved. Please consider proactively adopting these countermeasures and new technologies in your company’s overseas projects to build an efficient RTK operation system that overcomes communication infrastructure barriers. With reliable positioning technology, even previously challenging locations can become strong foundations for project success.