How On-site Crews Can Use RTK Without a Licensed Surveyor

Table of Contents

• What is RTK?

• Benefits of On-site Crews Using RTK Without a Licensed Surveyor

• Example Tasks On-site Crews Can Do with RTK

• How to Introduce RTK and Key Points

• Safety and Legal Notes

• Recommendation: Simple Surveying with LRTK

• FAQ

Accurate surveying is essential in many construction and civil engineering situations. However, always assigning a licensed surveyor to the site or outsourcing to a surveying specialist is not always practical. With limited personnel and budgets, there are increasing cases where on-site crews must carry out surveying themselves. That said, neglecting surveying accuracy carries the risk of construction errors and rework due to positional discrepancies.

In recent years, advances in satellite positioning technology known as RTK (Real Time Kinematic) have made centimeter-level (half-inch accuracy) high-precision surveying possible even with few personnel. Without dedicated large equipment or advanced specialist knowledge, an RTK-capable GNSS receiver can measure positions with high accuracy. As a result, tasks that previously relied on surveyors can now be handled easily by on-site crews.

This article explains RTK surveying that can be used at sites without a licensed surveyor. First, we describe what RTK is, how it works, and how it differs from standard GPS positioning. Then we introduce the benefits of on-site crews using RTK without a surveyor and specific tasks they can perform. We also cover procedures and key points for actually introducing and operating RTK, and touch on safety and legal considerations. At the end of the article, we introduce a simple surveying solution using RTK called LRTK, suggesting the possibilities for high-precision surveying that anyone can start with.

What is RTK?

RTK stands for Real Time Kinematic, a positioning technique that corrects GNSS positioning errors in real time to obtain highly accurate positional information within an error range of a few centimeters (half-inch accuracy). Standalone GPS positioning typically has errors on the order of several meters, but RTK drastically reduces those errors through specialized measurement methods. RTK technology has recently attracted significant attention in construction and civil engineering.

The basic principle of RTK is relative positioning (differential positioning) using two GNSS receivers. One receiver is placed at a known accurate coordinate point as a “base station,” and the other is operated as a “rover” that the worker carries while measuring. Both receivers simultaneously receive signals from multiple positioning satellites, and the base station sends the difference (error) between its measured result and the known true value to the rover in real time. By applying this differential correction, various error factors originating from satellite signals are canceled out, allowing the current position to be determined with centimeter-level (half-inch accuracy) precision. Precise surveying that was difficult before can now be performed immediately on-site using RTK.

Benefits of On-site Crews Using RTK Without a Licensed Surveyor

Amid labor shortages and aging technicians due to demographic changes, construction sites need to operate efficiently with limited personnel. Surveying that formerly required a multi-person team including veteran survey technicians is increasingly desired to be completed by fewer people as staffing becomes harder. RTK can greatly help solve these challenges even without a licensed surveyor. The main benefits of on-site crews performing high-precision surveying themselves include:

• Labor reduction and efficiency: RTK enables surveying tasks that previously required multiple people to be carried out by a single person. Because heavy tripods, prisms, and personnel to hold targets are unnecessary, other staff can be assigned to different tasks. Waiting for a surveyor to arrive or juggling schedules is eliminated, improving overall site productivity.

• Shorter schedules through speed: By walking around the site carrying a GNSS rover antenna, many points across a large area can be measured in a short time. This is far quicker than measuring point-by-point with a total station, enabling fast progress in tasks such as batter board layout and as-built checks. Since coordinates are obtained in real time during measurement, differences from design values can be checked on the spot and immediately reflected in construction, reducing interruptions from waiting on surveying or rework discovered later.

• Cost reduction: You can reduce the cost of outsourcing to surveying companies and the expense of maintaining an in-house dedicated surveying team. Once RTK equipment is introduced, many surveying tasks can be handled internally, reducing the number of external requests. Also, it is often unnecessary to purchase the full set of expensive optical surveying instruments (total stations, levels, etc.), lowering initial investment.

• Quality improvement: RTK’s high-precision positioning allows batter boards and structural placements to be set more accurately than before, preventing construction mistakes and rework and making it easier to ensure conformity to design. Additionally, detailed measurement data for as-built control can be obtained quickly, aiding in the preparation of quality assurance documents and inspection responses.

• Support for digital construction: With programs such as the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction,” the construction industry is advancing digital construction that leverages ICT and 3D data. Introducing RTK on-site is a first step toward 3D surveying and ICT-enabled construction. Being able to obtain and utilize accurate digital data in-house enhances client trust and contributes to future competitiveness.

Example Tasks On-site Crews Can Do with RTK

By using RTK positioning on-site, crews can perform many tasks that were traditionally left to surveyors or surveying teams. Below are major examples of tasks that on-site crews can handle with RTK even without surveying professionals.

• As-built surveying and terrain measurement: Using RTK for surveying existing conditions (current terrain) of roads, development sites, etc., allows workers to efficiently collect terrain data while walking the site. Where many cross-section points previously required time and manpower with a total station, an RTK-GNSS rover can measure many locations in a short time. For example, a terrain survey of around 50 points that traditionally took two people half a day might be completed by one person in a few hours with RTK. The collected terrain data can be used immediately as the basis for drawing and construction planning.

• Batter board layout and marking: RTK is effective for setting out positions and elevations of buildings and structures according to design. Where optical surveying instruments lose line-of-sight due to obstacles, GNSS positioning can directly measure positions if the sky is open. Even on sites with complex shapes or many surrounding obstacles, RTK enables rapid and accurate marking based on design coordinates, improving the efficiency and precision of layout work.

• As-built measurement and earthwork volume calculation: Measuring as-built surfaces of embankments and excavations in dams and development works with RTK allows detailed recording of finished terrain. From the numerous 3D coordinate points obtained, earthwork volumes such as fill and cut quantities can be calculated accurately. Because wide areas can be measured quickly, volume estimates based on only a few points can be replaced by more reliable calculations. Also, since personnel can measure required locations immediately after construction to check differences from design, as-built inspections that were often postponed can be completed on the spot.

• Infrastructure inspection and maintenance management: RTK is useful for maintenance tasks of existing infrastructure such as roads and bridges. Precisely recording the positions of anomalies like cracks or settlement makes it possible to re-measure the same locations later to track displacement. Retaining digital coordinate data rather than roughly noting positions on paper drawings improves the accuracy of inspection and maintenance records.

• Simple 3D surveying: Combining RTK with smartphones or drones enables easy acquisition of 3D surveying data. For example, flying an RTK-capable drone over a site can create a high-precision terrain model without installing numerous ground control points. Also, coupling a smartphone’s LiDAR sensor or camera with RTK allows acquisition of point-cloud data without an expensive laser scanner. These techniques make 3D surveying and documentation affordable even for small sites.

How to Introduce RTK and Key Points

When an on-site crew actually introduces and operates RTK surveying, there are several key points to keep in mind. Traditionally, a full set of expensive surveying equipment and radio devices was required, but recently user-friendly RTK solutions have appeared. Below are basic procedures and preparations to know when using RTK for the first time.

• Prepare RTK-capable equipment: First, procure a GNSS receiver that supports high-precision positioning (an RTK receiver). Traditional setups required a two-unit set for a base station and a rover, but if you do not set up your own base station, a single rover may suffice by using the Geospatial Information Authority of Japan’s permanent station network or private correction services. Recently, ultra-compact RTK receivers that can connect to smartphones have appeared; such devices offer high portability and ease of transport to the site.

• How to receive correction information: RTK positioning transmits correction information in real time from the base station to the rover to correct positioning errors. Communication methods include radio and internet-based approaches. When using radio, equip both the base and rover with modules such as specific low-power radios to send correction information directly (note that some frequency bands require radio station licensing). If there is network coverage on site, it’s convenient for the rover to connect via a smartphone to internet-based correction services like the Geospatial Information Authority’s permanent station network or VRS, and receive data. In Japan, the Quasi-Zenith Satellite System “Michibiki” also provides a centimeter-level correction service (CLAS). In mountainous areas where cellular signals do not reach, receiving corrections directly from satellites can be effective, so choose the best method according to site conditions.

• Setting up the base point: If you install your own base station, secure a location for the base station antenna at a known-accurate coordinate point (a known point) near the site. If there are no public control points or known points nearby, you can set up a temporary base point and perform RTK surveying relative to it. However, in that case the measured coordinates are relative to the temporary reference and you must later tie them to public coordinate systems with offset correction. In any case, place the base station antenna in a spot with as open a view of the sky as possible and mount it firmly to stabilize accuracy (if using network RTK, a personal base station is not necessary).

• Use surveying apps: To view and record positioning data from the GNSS receiver on-site, use dedicated software or surveying apps for smartphones/tablets. Many RTK receivers come with smartphone/tablet apps that display real-time coordinates from a Bluetooth-connected receiver and let you record and save point names and notes. Apps often offer settings for Japan’s geodetic systems (plane rectangular coordinates, geoid heights, etc.), allowing measured data to be directly used for drawing and as-built control.

• Pre-checks and practice: After introducing RTK equipment, perform operational checks and practice before going to the actual site. For example, use a known point in your company parking lot as a base station and measure several surrounding points as a test. Comparing measured values with known coordinates verifies correct equipment operation. Also check how long it takes the rover to achieve a “FIX” solution (integer ambiguity resolution, indicating sufficiently small error) and the satellite signal acquisition conditions so you won’t be confused on the actual site. Additionally, test positioning in environments with poor satellite reception, such as mountainous areas or under trees, and consider measures such as choosing measurement locations or times to suit site conditions.

Safety and Legal Notes

When on-site crews perform surveying using RTK, attention is required for safety and legal compliance. Below are particularly important points to note.

• Ensuring work safety: Even when surveying with a small crew, prioritize worker safety. Wear helmets and safety vests when installing or operating surveying equipment, and pay attention to nearby heavy machinery and vehicle movement. When using long GNSS antenna poles, watch for overhead power lines and ground obstructions, and avoid working in severe weather (e.g., thunderstorms with lightning risk). Even when working alone, keep in contact with other workers when possible and prepare for emergencies.

• Legal treatment of surveying results: If surveying data is used internally for construction management, unqualified personnel operating RTK for measurement does not pose legal issues. However, be careful when using obtained survey data as official results (public survey outcomes or boundary determination). Under Japan’s Survey Act, planning and implementing public surveys by national or local governments must involve licensed surveyors. Boundary determination and cadastral surveys that have legal effect on land boundaries must be performed by specialists such as land and house investigators. Therefore, even RTK survey results intended for official drawings or registration must go through verification and procedures by qualified personnel. Conversely, for internal purposes like as-built control and quantity measurement during construction, on-site crews may use RTK measurements without issue.

• Compliance regarding radio use: Some RTK systems use radio communications to send correction information from a base to a rover. When using high-power radios in bands such as UHF, a radio station license under the Radio Act may be required. Specific low-power radios commonly used in Japan do not require a license but have limited range. In contrast, network RTK that uses cellular networks or CLAS from quasi-zenith satellites does not require special radio licensing. When introducing an RTK system, confirm the communication method and legal requirements in advance and operate without violations.

• Accuracy control and records: Even without a surveyor present, ensure measures to maintain the reliability of survey data. When measuring important points, take multiple measurements at the same location to confirm stable values, or re-measure later for comparison. Record and save measurement results along with date/time, measurer, and equipment used so they can be verified later. If doubts arise about survey results, detailed records aid in investigating causes and making corrections.

Recommendation: Simple Surveying with LRTK

Finally, as an example of an RTK solution that anyone can use without a licensed surveyor, we introduce our company’s LRTK. LRTK is a pocket-sized RTK-GNSS receiver developed by a startup originating from the Tokyo Institute of Technology and is attached to and used with a smartphone (e.g., iPhone or iPad). It is an ultra-compact device weighing about 125 g, with a thickness of about 13 mm (0.51 in), and runs on an internal battery so no large external power source or tripod is required. By connecting to a smartphone, it can achieve centimeter-level (half-inch accuracy) positioning comparable to conventional large surveying instruments, and its portability makes it easy to take out and use for surveying whenever needed.

With just one LRTK receiver attached to a smartphone, you can cover almost all the surveying tasks introduced above. Hold the antenna over the point you want to measure and tap a button on the smartphone to record that point’s latitude, longitude, and height with high accuracy. The obtained coordinates are automatically converted to Japan’s plane rectangular coordinate system and elevation (geoid height) and saved together with point names, date/time, and notes. It also includes functions to instantly calculate distances between two points and the area enclosed, and a navigation function to guide actual stake-out positions toward target points on design drawings. Furthermore, it features 3D scanning using the smartphone camera or LiDAR, and an AR (augmented reality) function that overlays designed 3D models onto site imagery, covering a wide range of on-site needs in one device. Measured data can be uploaded to dedicated cloud storage with one tap and shared instantly with office staff.

LRTK is a multi-frequency GNSS receiver and can receive the centimeter-level correction signal CLAS provided by Japan’s Quasi-Zenith Satellite System “Michibiki.” Therefore, even outside cellular coverage, high-precision real-time positioning can continue as long as CLAS is receivable. Compared with traditional RTK surveying equipment, LRTK can be introduced at a dramatically lower cost and is an ideal on-site DX tool for the “one person, one device” era. By using LRTK for simple surveying, sites that cannot assemble a full surveying team can achieve high-precision surveying, dramatically improving productivity and construction quality.

FAQ

Q: Do I need a qualification to perform RTK surveying? A: No special national qualifications (such as a licensed surveyor) are required to operate the equipment itself. Anyone can perform RTK surveying after receiving basic training and becoming proficient in its use. However, note that when using radio equipment to communicate data from a base station, a radio station license may be required depending on the frequency band used (network RTK over communication lines or satellite-based CLAS do not require such a license). Also, when using survey data for legally effective purposes such as land boundary determination, always go through verification and procedures by qualified surveyors or land and house investigators.

Q: Can a smartphone’s built-in GPS replace RTK? A: General smartphone GPS (standalone positioning) has accuracy of only about 5–10 m and is far from the precision required for construction surveying. However, if you combine a smartphone with an external RTK-capable receiver, centimeter-level positioning becomes possible. In other words, you can augment a regular smartphone GPS with RTK high-precision functionality. For example, attaching an ultra-compact RTK receiver like LRTK to a smartphone enables easy high-precision on-site surveying.

Q: How accurate is RTK positioning? A: Under favorable conditions, RTK can achieve horizontal position errors within a few centimeters (half-inch accuracy) and vertical errors on the order of a few centimeters. This is orders of magnitude more accurate than standalone GPS, which has errors of several meters. However, accuracy can degrade if the surrounding environment prevents sufficient satellite reception. Vertical accuracy tends to be worse than horizontal and may sometimes exceed a few centimeters of error.

Q: Can RTK be used at mountain sites without cellular coverage? A: Yes, RTK positioning is possible in areas without cellular coverage. For example, Japan’s Quasi-Zenith Satellite “Michibiki” provides the CLAS centimeter-level correction service, allowing reception of correction information directly from satellites without an internet connection. Setting up your own base station in advance and operating via radio communication is another effective method. Choose the optimal operational approach according to the site’s communication conditions to achieve high-precision positioning even in mountainous areas.

Q: Is it difficult to perform surveying alone? A: Modern smartphone-connected RTK devices are designed to be easy to operate solo. Apps provide intuitive user interfaces that guide you with sounds or on-screen prompts as you approach a target point. There is no need to carry heavy equipment or operate complex instruments; with a little practice, a single person can perform high-precision surveying adequately.

Q: Do bad weather or surrounding obstacles affect RTK positioning? A: Heavy rain or snow has relatively little direct effect on satellite positioning. However, the surrounding environment does matter. In forests or near tall buildings, satellite signals can be blocked or reflected, degrading RTK accuracy or preventing a positioning solution. Measuring in as open a sky as possible and choosing times when satellite geometry (elevation and distribution) is favorable can help reduce errors.

Q: If we have RTK, are total stations or levels no longer necessary? A: In environments where satellite positioning does not reach—such as tunnels or indoors—traditional instruments like total stations (TS) and optical levels are still necessary. Also, for short-distance tasks requiring millimeter-level control (precise leveling or equipment installation), optical instruments may be more reliable. Therefore, while RTK streamlines many tasks, it does not entirely replace other surveying tools. It is practical to use RTK alongside conventional TS and levels depending on the application.

Q: How much does it cost to introduce RTK equipment? A: In the past, a full RTK surveying set required an investment of several million yen, but today compact and inexpensive devices make introduction relatively affordable. Specific costs vary by model and configuration, but free correction information sources such as the Geospatial Information Authority’s VRS or the Michibiki CLAS can significantly reduce operating costs. Smartphone-attached RTK receivers that have become widespread in recent years have drastically lower initial costs compared to traditional setups, making them accessible for individuals and small businesses.