Table of contents

• Is RTK sufficient for stakeout work?

• Can as-built surveys be done with RTK alone?

• Is it OK to use RTK for boundary surveys?

• Use of RTK in route surveys

• Advantages of RTK-only surveying

• Precautions and limitations of RTK-only surveying

• Points to judge whether RTK alone is OK

• Simple surveying with LRTK

• FAQ

Is RTK sufficient for stakeout work?

In stakeout (positioning) work, it is necessary to place reference stakes or bolts for a structure accurately. Especially for foundations of high-rise buildings or bridges, there are cases where the stake center (pile center) must be set with an error of only a few millimeters. Traditionally, such precise stakeout required precise surveying with a total station (TS) and multiple workers. However, by using RTK-GNSS positioning (real-time kinematic high-precision GPS), under certain conditions it has become possible for a single person to perform stakeout positioning.

The accuracy of RTK positioning for stakeout, in open environments, is about 2–3 cm (0.8–1.2 in) horizontally. This accuracy is sufficient for stakeout tasks that tolerate errors on the order of several centimeters, such as roadworks or land development sites. For example, placing stakes across a large development area or marking a road centerline can be done efficiently by setting up an RTK receiver and guiding the stakeout according to design coordinates. Because RTK does not require line-of-sight, it can also directly obtain stake coordinates in places where traditional surveying sight lines are difficult to secure (large sites or locations with obstacles), as long as the sky overhead is open.

That said, RTK is not万能 for all stakeout tasks. In urban narrow lots, under elevated structures, or inside forests where the sky view is poor, RTK positioning tends to become unstable. Poor satellite reception can produce errors of tens of centimeters or cause the solution to become a float solution instead of fixed. In such cases, it is desirable to verify using traditional TS surveying or batter boards (reference marking using mason's string). For stakes that require particularly strict tolerances (e.g., reference stakes for critical structures requiring millimeter-level accuracy), it is safer to use RTK only for provisional positioning, then confirm final placement with detailed measurements—i.e., employ a two-step checking system. Introducing RTK greatly improves efficiency and reduces labor in stakeout work, but by choosing when to use or combine it with conventional techniques according to site conditions, accuracy and reliability can be ensured.

Can as-built surveys be done with RTK alone?

An as-built survey verifies whether constructed structures or terrain match the design. It measures completed forms such as fill/cut heights and slopes for earthworks, pavement thickness, and dimensions of excavated foundations to inspect quality. Because as-built verification often requires measuring many points in a short time, RTK-only surveying is highly effective.

With RTK-GNSS, one person can walk around a large site holding an antenna and record coordinates at many locations in succession. Typical RTK accuracy (horizontal 2–3 cm (0.8–1.2 in), vertical 3–5 cm (1.2–2.0 in)) usually falls within allowable tolerances for as-built measurements. For example, in checking finished heights of development sites or slopes of road subgrades, errors of several centimeters are rarely a practical problem; reducing human variability and missed points between measurement locations is often more important. As-built surveys with RTK can measure fine grid points to capture surface undulations in detail, which leads to improved quality-control accuracy compared with manual methods.

However, there are cautions when using RTK for as-built surveys. RTK vertical accuracy tends to be worse than horizontal, so when strict control of elevation is required, supplementary measurements are advisable. For instance, when checking concrete pavement thickness where millimeter-level height verification is needed, you might check height reference points with an optical level (spirit leveling) or reconcile RTK heights with known bench marks to correct them. Also, if satellite reception deteriorates during RTK surveying, instantaneous errors can increase. When recording important as-built data, measuring the same point multiple times to confirm stability, or re-measuring on another day for comparison, is an effective cautious practice.

Overall, as-built surveys can be handled with RTK alone for the majority of tasks, providing major benefits in speed and coverage. RTK technology that allows one person to quickly measure large areas is a tool that can dramatically improve quality-control efficiency.

Is it OK to use RTK for boundary surveys?

In boundary surveys such as land parcel and site surveys, point locations have legal and contractual significance, so measurements must be particularly careful. It is possible to use RTK to determine coordinates of boundary monuments or stakes, but there are several points to be cautious about.

First, regarding the accuracy required for boundary surveys, in many practical cases accuracy within a few centimeters is acceptable. RTK can achieve about 2–3 cm in good conditions, so technically it can be used to measure boundary points. In practice, network-type RTK using the Geospatial Information Authority of Japan’s electronic reference point network (VRS and similar) is increasingly being adopted for public surveys and cadastral surveys. RTK allows obtaining boundary coordinates in real time on site and checking deviations against maps immediately, enabling efficient workflows.

However, verification and corroboration are indispensable when using RTK alone for boundary surveys. Specifically, procedures such as measuring RTK-derived boundary point coordinates multiple times to average them, or measuring distances between adjacent boundary points and comparing them to design values to check error ranges, are important. Japanese public surveying guidelines recommend that when measuring boundary points with RTK, re-observations and checks of closure errors against known points be performed, and that differences be confirmed to be within 3 cm (1.2 in).

Also pay attention to the environment where boundary monuments are located. Boundary markers are often placed near trees or beside buildings where GNSS signals are hard to receive. In such locations, avoid forcing RTK positioning; consider alternative methods such as distance measurement with a TS. A practical approach is to obtain provisional coordinates with RTK, cross-check them with recorded plans and existing documents, and then finalize positions with optical surveying—this two-step approach is reassuring.

In conclusion, RTK can be a powerful auxiliary tool for boundary surveys, but relying solely on RTK requires caution. Take advantage of the real-time coordinate acquisition while verifying important boundary points with conventional methods when necessary; this is the basic stance when using RTK for boundary surveying.

Use of RTK in route surveys

Route surveys refer to surveying and design work along linear structures such as roads and railways. In route surveys, which require measuring many terrain points and centerline points along long routes, RTK-GNSS is particularly powerful. Because RTK can directly obtain absolute coordinates even for points far from a base station, it enables efficient acquisition of measurement points over long distances.

Traditional route surveying generally proceeds by observing with a total station from established known points or traverse lines at set intervals. That method requires physically moving along and sighting each point in turn, so for long routes it is very time-consuming. With RTK, a surveyor can simply walk along the road carrying a rover and immediately obtain coordinates for designated points (for example, points every 50 m (164.0 ft) along the road centerline or key terrain points). Unless there are obstacles, RTK’s ability to let one person continuously measure a survey line that extends for kilometers is a major advantage.

Points to watch when using RTK for route surveys include distance from the base station and communication coverage. When using a private base station, accuracy gradually degrades if too far from the base, so consider adding or relocating base stations as needed. However, in Japan network RTK services based on electronic reference points are well established, providing nearly uniform cm-level accuracy (cm-level accuracy (half-inch accuracy)) nationwide. By using appropriate network RTK services, you can continue surveying long routes without being overly concerned about baseline distance.

Another challenge is tunnel alignments and forested sections in mountainous areas. RTK is unusable inside planned tunnel sections where the sky is blocked, so you need to switch to ground-based surveying (total station) before and after such sections to connect measurements. Dense forest canopy can reduce satellite tracking and lower accuracy; in those cases supplement the difficult sections with optical surveying, or measure with the antenna mounted on an extended pole to improve sky view.

Overall, route surveying is one of the fields that benefits most from RTK. RTK can rapidly cover wide areas, making surveying for roads, pipelines, etc., much more efficient. There are many cases where terrain surveys that used to take several days can be completed in one day. By preparing suitable communication environments and correction services and combining other methods as needed, RTK alone can cover most of the route surveying workload.

Advantages of RTK-only surveying

As described above, using RTK alone can reduce labor and increase efficiency across various surveying tasks. Here are the main advantages of RTK-only surveying.

• One-person operation: Surveys that traditionally required two or more people can be done by one person with RTK. There is no need to have separate instrument operator and target holder, enabling quick response even at sites with labor shortages.

• Rapid measurement over wide areas: GNSS surveying directly acquires absolute coordinates, so points far apart can be positioned without sequential line-of-sight observations. This allows quick acquisition of many points while moving, greatly reducing work time on large sites or long routes.

• Real-time confirmation of results: RTK provides coordinate values on site in real time, allowing immediate review of measurement results and additional measurements or re-measurement as needed. For example, if an as-built unevenness is detected, the surveyor can immediately take additional surrounding measurements or judge differences against design values on site.

• No need to re-set instruments per point: With a total station, repeated setup and back-sighting are required for each measurement point, but with RTK, as long as a base station (or network correction) is stable, you can simply carry the rover and measure continuously. This reduces the number of equipment setups and takedowns and simplifies site workflow.

• Not reliant on highly specialized skills: Methods like batter boards with tape measures or TS line-of-sight depend on skilled operators. RTK instruments display positioning results digitally, so once basic operations are learned, even those with limited surveying experience can work to a reasonable accuracy. When combined with intuitive guidance software, RTK becomes even more user-friendly.

Thus, RTK-only surveying offers many advantages in reducing personnel, time, and effort while achieving high accuracy. In today’s construction industry, DX (digital transformation) and i-Construction promotion have made GNSS-based labor-saving surveying increasingly important. RTK is a key technology in this trend.

Precautions and limitations of RTK-only surveying

Even convenient RTK-only surveying has challenges and limitations to be aware of. Understanding these points, which are two sides of the coin of the advantages, is essential for safe and reliable operation.

• Dependence on the positioning environment: RTK accuracy is greatly affected by satellite signal reception. Excellent sky visibility with ample satellite tracking yields high accuracy, but in downtown high-rise areas or wooded zones, multipath (signal reflection) and satellite loss can increase errors. Experiments show that in urban areas average errors may be around 5 cm (2.0 in) though occasionally exceeding 10 cm (3.9 in), while in open flat areas errors typically remain within 2–3 cm (0.8–1.2 in). Therefore, do not over-rely on RTK in poor environments and be prepared to switch to other surveying methods as needed.

• Vertical accuracy and elevation control: GNSS vertical accuracy is generally worse than horizontal. RTK can have elevation errors of several centimeters, making it unsuitable in some cases for strict height control. To ensure vertical accuracy, reconcile with elevation bench marks obtained by precise leveling, or supplement critical elevations with optical leveling.

• Initialization and satellite count: RTK achieves full accuracy only when a fixed solution (Fix) is obtained. Satellite geometry (GDOP) and radio reception conditions can cause delays in obtaining a Fix after starting positioning, and a fixed solution may revert to a float solution. Before work, check satellite configuration forecasts, choose time windows with favorable geometry if possible, and avoid measuring when satellite availability is low.

• Dependence on equipment and communication: Network RTK depends critically on a communication link. In mountainous areas where mobile communications are out of range, correction data cannot be received and network RTK cannot be used. Battery depletion or receiver faults can halt work. Prepare backup power and alternative plans for offline operation (for example, switching to a private base station or temporarily performing static/post-processing surveys).

• Compliance with regulations and inspections: When submitting survey results officially or undergoing inspections, be prepared to explain GNSS surveying methods. For cadastral surveys, for example, inspectors may require documentation such as observation logs and accuracy verification results even for GNSS-derived values. Keep correction data and accuracy evaluation logs properly so results can be explained later.

By attending to the above points, the reliability of RTK-only surveying can be greatly improved. The key is not to leave everything to RTK. It is a convenient tool, but by applying traditional surveying knowledge, performing double checks, and considering the environment, you can maximize RTK’s benefits while controlling risks.

Points to judge whether RTK alone is OK

When deciding on site whether "this task can be done with RTK alone?", check the following points to judge feasibility.

• Required accuracy level: If the required accuracy is on the order of a few centimeters, RTK alone is likely suitable. Conversely, if millimeter-level accuracy is required (e.g., precise structural stakeout or precise settlement measurement), RTK alone may be inadequate and additional surveying methods should be considered.

• Survey environment: Check sky openness. If there are no tall buildings or dense trees nearby and the sky is widely visible, RTK positioning conditions are favorable. In contrast, in tunnels or between tall buildings where satellite reception is poor, RTK alone will be difficult. In such cases, plan to relocate measurement points or switch to alternative methods.

• Work area and efficiency: The larger and more numerous the measurement points, the greater RTK’s efficiency advantage. Use RTK proactively for broad-area overview surveys and long routes. Conversely, for very small areas (a few square meters) where dense, high-resolution measurements are needed, optical surveying may suffice without GNSS.

• Known points and reference systems: Confirm whether site coordinate references already exist. If managing coordinates in a public geodetic system (e.g., WGS84), network RTK provides direct coordinates. For local arbitrary coordinate systems, measuring one or two known points with RTK allows easy transformation to local coordinates. Consider the effort to establish reference points separately; if RTK can secure references simultaneously, it is efficient.

• Backup plans: Confirm whether you have contingency plans if RTK becomes unusable. For example, prepare a mobile base station set if communication coverage may be lacking, or plan to verify key points with a TS for accuracy checks. If there is no alternative and operations rely solely on RTK, the risk is high and overreliance should be avoided.

By judging these points comprehensively, you can determine which tasks are suitable for RTK-only operation. Use RTK actively where requirements are met, and combine other surveying methods under difficult conditions—this flexible approach represents smart surveying in the RTK era.

Simple surveying with LRTK

Maximizing the benefits of RTK technology also depends on having user-friendly equipment and systems. Traditionally, performing RTK surveys required specialized, expensive equipment and complex setup. Today, solutions like LRTK make it easy for anyone to introduce RTK surveying.

LRTK attaches a compact high-performance GNSS antenna to a smartphone or tablet and receives correction information via network to achieve centimeter-class positioning (cm-level accuracy (half-inch accuracy)). Without dedicated large instruments, a handheld device becomes a high-precision GNSS receiver, and intuitive app operations allow surveying. For example, with LRTK, even those with limited surveying experience can perform simple surveys and precise stakeout. There are emerging use cases where stakes that used to require two people can be guided reliably by one person using LRTK combined with AR displays.

The emergence of LRTK series has significantly lowered the barrier to adopting RTK-only surveying for small and medium construction firms and local governments. These latest RTK solutions, compatible with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction policy, are attracting attention as tools that dramatically improve site productivity and surveying accuracy. If you wonder what to procure to perform one-person RTK surveying, LRTK packages typically integrate the necessary device, app, and cloud services, making adoption smooth. Considering cost and ease of operation, companies without dedicated surveying departments can now handle surveying more easily.

As RTK adoption grows, surveying will increasingly shift from a craftsman’s skill to a digital task anyone can perform. As a pioneer of that change, simple surveying with LRTK has the potential to transform on-site norms.

FAQ

Q: How accurate is RTK surveying? Is RTK alone really OK? A: With RTK-GNSS surveying, under good conditions horizontal accuracy of about 2–3 cm (0.8–1.2 in) and vertical accuracy of about 3–4 cm (1.2–1.6 in) can be obtained. This meets the accuracy required by many civil surveying and construction-management tasks. However, in places surrounded by buildings or in forests, temporary errors of tens of centimeters can occur, so supplementing with conventional methods depending on environmental conditions should be considered. For critical points, double-checking by measuring with another method after RTK is reassuring.

Q: If I have RTK, do I no longer need total stations or levels? A: RTK is very useful, but it does not completely replace total stations (TS) or optical levels. Each has its strengths. RTK excels at quickly surveying many points over wide areas and enabling one-person operations in places where line-of-sight is difficult, but TS and levels are superior for millimeter-level precision and detailed surveying where direct sighting is possible. Ideally, use RTK to cover tasks it handles efficiently and supplement final high-precision work with TS or levels to combine the advantages of both.

Q: What is required to use network RTK? A: To use network RTK (VRS and similar), you need a GNSS receiver (rover) and an environment to receive correction data via the Internet. Specifically, a mobile-communication-capable device (a receiver with a SIM card or a connected smartphone) and subscription to a correction-data service are required. In Japan, there are private GNSS correction services and services utilizing the Geospatial Information Authority of Japan’s electronic reference points. Receiving such correction data allows RTK positioning without setting up your own base station. Note that network RTK cannot be used where there is no communication coverage; in such cases, switch to a local base station broadcasting corrections or to post-processed positioning.

Q: I am worried about introducing RTK for the first time. Is it easy to use? A: Recent RTK equipment and software are user-friendly, and basic operations are not very difficult. Systems like LRTK let you follow guided steps on a smartphone app to perform surveys, making them usable even with limited expertise. To get the best accuracy, you still need to learn some tips for satellite reception (keep the antenna unobstructed, ensure sufficient height, etc.) and become familiar with equipment handling. Start practicing on simple sites, check measurement variability, and gain experience. If you have questions, consult the manufacturer or service provider. With proper learning, newcomers can become proficient in RTK surveying in a relatively short time.

Q: What is simple surveying with LRTK? A: LRTK is a solution that combines a compact RTK-GNSS receiver usable with smart devices and a dedicated app. This enables centimeter-class surveying (cm-level accuracy (half-inch accuracy)) without heavy equipment or complicated setup. For example, attaching an LRTK receiver to a smartphone and walking the site acquires high-precision position data automatically, which can be managed and shared in the cloud. Tasks that used to be performed by experienced surveyors, such as stakeout and as-built management, can be carried out accurately by less-experienced staff using LRTK’s intuitive AR navigation. In short, simple surveying with LRTK is a new survey method that realizes RTK-level precision with more user-friendly equipment and operations, and its effectiveness is being verified at many sites.