Table of Contents

• Setup: Pre-survey Preparation for RTK

• Base Station and Rover Configuration

• Leveraging Network RTK

• Data Acquisition and Field Work with RTK

• Post-processing RTK Survey Data

• Deliverable Use via CAD Integration

• U.S. Accuracy Standards and Data Submission Formats

• Spread of Mobile RTK and New Surveying Methods

• RTK Easily Adoptable in Japan: LRTK Phone and Its Technology

Setup: Pre-survey Preparation for RTK

RTK surveying is a method that corrects GNSS positioning errors in real time to achieve centimeter-level accuracy (half-inch accuracy). To realize that accuracy, meticulous setup before fieldwork is indispensable. First, confirm the coordinate system and geodetic datum to be used for the project. In the U.S., state plane coordinate systems (NAD83) or UTM coordinate systems are often used, so decide in advance on the coordinate system and datum to be used. Also, investigate beforehand whether there are known control points near the site, and if available, obtain their coordinate values. If no control points exist, plan to obtain reference coordinates using network RTK or post-processing corrections as described below.

Next, prepare the full set of equipment to be used. Bring GNSS receivers (for base station and rover), controllers or data collectors (tablets or smartphones are increasingly used), communications equipment (radios or mobile routers), and batteries to the site. Check battery levels before departure and carry spare batteries. Ensure firmware and positioning applications on the equipment are up to date. Also, preconfigure and test communication methods between base and rover (radio frequency settings or NTRIP connection information) so that connections in the field proceed smoothly.

On site, first select a location to set up the base station. An open area with good sky visibility and minimal obstructions from buildings or trees overhead is ideal. Placing the base at a higher position expands communication range with the rover. Choose stable ground where people and vehicles will not interfere, set up a tripod, and securely fix the base station. Thorough preparation like this ensures subsequent RTK surveying steps proceed smoothly and maintains accuracy and efficiency.

Base Station and Rover Configuration

In RTK surveying, typically one GNSS receiver operates as the base station and another as the rover. The base station is installed at a known coordinate position and generates real-time correction data based on that position. The rover moves while observing survey points and uses the correction data received from the base station to compute its position with high accuracy.

When configuring the base station, the first important step is determining the base station coordinates. How you set the base station’s position determines the reference for the resulting positioning. There are several options:

• Install on a known point: Set the base station on a control point whose precise coordinates (latitude, longitude, height) are already known, and use that known coordinate as the base station position. This method ties measurements directly to an existing geodetic framework, yielding high absolute accuracy.

• Average positioning from observations: If no known point is available on site, install the base station at an arbitrary location and perform GNSS observations for a few minutes to compute an averaged coordinate (also called survey-in). Use this averaged coordinate as the provisional base station position. Note that while relative positioning with the rover is accurate, the absolute accuracy of the base station coordinate derived from a short averaged survey may remain on the order of meters.

• Fit to local coordinates: If you need to align with a site-specific coordinate system (for example, a local construction grid or drawing coordinate system), operate the base station at an arbitrary position, calculate the difference between the acquired coordinates and the existing drawing coordinates, and apply a local transform to correct measurements. This makes measured results conform to the project’s coordinate system.

After setting the base station coordinates, measure the receiver antenna height (the distance from the ground or mark to the antenna reference point) accurately and enter it into the controller. Errors in height entry directly affect elevation results, so take care. Mount the base station equipment on the tripod, use a level to ensure the antenna is plumb, and secure it. Then switch the base station to correction-data transmission mode. If using UHF radio, match frequency and channel with the rover and begin transmission; if using a network, enable data communications and start NTRIP streaming. Once the base station is operating normally and outputting correction data, ensure the rover is able to receive that information.

The rover also requires preparation before starting observations. Mount the rover receiver on a pole or staff and check vertical alignment with a bubble level. Measure the rover antenna height and enter it into the controller. On the rover controller (or app), confirm the receive mode is set to RTK rover mode and configure communications so correction data from the base station can be received. When radio between base and rover is connected or NTRIP is established, the rover receiver will begin receiving correction data (such as RTCM), and the positioning engine will start differential calculations. Monitor the rover screen for the real-time solution status and wait until a "Fix (fixed solution)" is obtained. A Fix indicates the integer carrier-phase ambiguities have been resolved; in this state, the rover reaches centimeter-level accuracy (half-inch accuracy). Immediately after initialization the display may show "Float (float solution)" while errors are still larger, so wait until sufficient satellites are tracked and communications are stable. Usually convergence to Fix occurs within tens of seconds to a few minutes. Once a Fix is obtained, full-scale observations with the rover may commence.

Leveraging Network RTK

Instead of setting up your own base station as described above, it is also common in the U.S. to use network RTK services. Network RTK (real-time reference networks) use data from multiple reference stations (CORS: Continuously Operating Reference Stations) distributed over a wide area to generate virtual reference stations near the user and provide correction data. State geodetic offices and private companies operate many RTK networks, and surveyors subscribe to these services to receive correction data via the internet.

When using network RTK, there is no need to set up a base station on site. By connecting the rover’s built-in communications modem or a connected smartphone to the internet and logging into the specified NTRIP caster, optimal reference station data are delivered automatically. For example, when a rover connects to a state RTN (Real-Time Network) service, data from several surrounding reference stations are integrated based on the rover position and corrections are provided as if a virtual base station existed near the rover. This allows centimeter-level positioning without deploying your own base station.

Many U.S. states have public RTK networks that surveyors and contractors routinely use—for example, Ohio’s ODOT network and California’s CRTN—providing broad reference-station coverage. Private subscription services from companies like Trimble and Leica are also common. The advantages of network RTK are rapid initial setup and consistent accuracy over wide areas. With only a rover on site, power it on and begin surveying within minutes. This saves time when visiting multiple sites in one day by eliminating the need to set up and tear down a base station at each location. Also, network corrections are modeled to minimize accuracy degradation over distance, so corrections can be effective even if reference stations are more than 10 km away.

Be aware that network RTK requires internet connectivity and involves service fees. In mountainous or areas with poor cellular coverage, communications may be unstable and accuracy can decline. For this reason many U.S. survey teams choose between operating their own base stations and using network RTK depending on the area. In urban or well-connected locations they use network RTK, while in remote sites they revert to the traditional base-and-rover approach to ensure stable positioning.

Data Acquisition and Field Work with RTK

Once base and rover are ready and the rover has a Fix solution, proceed to observe survey points. In the field, the basic rule is to place the rover precisely on the point to be measured. Align the pole tip (prism rod tip or the receiver’s plumb point) over the stake or reference mark and keep the pole vertical. When using a tripod, place a marker under a tripod leg to indicate the point and fix the receiver directly above it.

At each survey point, plan the observation time and number of measurements to obtain reliable data. Although RTK provides high-precision coordinates in real time, instantaneous readings include small random fluctuations. For each point, continue positioning for a few seconds to a few tens of seconds and wait until the position stabilizes. Survey controllers and apps often have functions to average measurements—for example, record averaged coordinates over 5 seconds or 30 seconds. Even short measurements can be improved by averaging multiple observations. In one case, the standard deviation of a single observation was about 12 mm, while averaging for one minute reduced the scatter to 8 mm. Averaging and multiple observations reduce random errors and yield stable positioning in the field.

Monitor positioning status and accuracy indicators on the controller screen during observations. Check that HDOP/PDOP values are not excessive, that the Fix is maintained, and that estimated errors per axis (RMS) are within acceptable limits. If the solution temporarily reverts to Float or PDOP worsens, consider transient obstructions or radio interference; wait a short time or raise the pole height as needed. Record point data only when a stable Fix is maintained.

When surveying multiple points, efficient procedures are important. For many terrain points on flat ground, the rover operator can walk and record points at regular intervals using a continuous-measurement (topographic) mode. For stakeout or layout work such as placing building corners or boundary stakes, use the controller’s guidance to walk the rover to target coordinates derived from CAD drawings. The controller displays real-time guidance such as "5 cm east, 3 cm north to the target," enabling a single operator to place points accurately.

Verification measurements are essential for field quality control. Observe known control points or check points with the rover before and after fieldwork and compare coordinate differences to verify overall survey accuracy. For example, if the same known point measured at the start and end of the day shows negligible difference, positioning stability over the day is confirmed. Large deviations may indicate a drift of the base station coordinates or equipment malfunction, so recheck data and remeasure if necessary.

As described above, RTK fieldwork should proceed while continuously checking observation results. Using real-time results to identify and eliminate sources of error in the field simplifies later processing and increases confidence in deliverables.

Post-processing RTK Survey Data

Data collected in the field with RTK are basically already corrected and high-precision. However, for surveys with stringent accuracy requirements, additional verification and adjustment through post-processing may be performed. Especially when the base station coordinate was assumed during fieldwork (base placed on an unknown point or averaged in place), it is necessary to determine the true base coordinates later and apply a uniform correction to all observed points.

In the U.S., OPUS (Online Positioning User Service) provided by NGS is commonly used to validate base station coordinates. Record a few hours of GNSS observation data at the base station on site, then upload the raw data (RINEX format) to OPUS, which returns latitude, longitude, and ellipsoid height with centimeter-level accuracy. Compute the difference between this precise reference coordinate and the provisional base coordinate used in the field, and apply the offset to all rover observation points to translate the dataset into the correct reference frame. With such post-processing, standalone RTK observations can be aligned with the national coordinate system even without network dependence.

Post-processing also includes quality control of rover-acquired points. For example, if the same point was observed multiple times, adopt the mean value or remove outliers to determine the final coordinate. Heights are usually acquired as ellipsoid heights by GNSS in the field, but for practical purposes convert them to orthometric heights using a geoid model. In the U.S., geoid models (e.g., GEOID18) are used to convert ellipsoid heights to NAVD88 orthometric heights, and results are presented in that datum. Controllers may apply this conversion automatically during data collection, or it can be applied in post-processing software.

To assure survey quality, prepare an accuracy report in post-processing. Summarize estimated errors (horizontal and vertical) for each point and observation conditions (PDOP, number of satellites, observation times) to confirm compliance with standards. If any points fall outside tolerances, consider additional measurements or exclusion. After these checks and corrections, finalize the coordinate list and proceed to CAD integration.

Deliverable Use via CAD Integration

High-precision field data are ultimately imported into CAD software or GIS systems for use. A major advantage of RTK surveying is the ability to directly reflect field-acquired coordinates in design drawings and topographic maps. U.S. surveying practice standardizes workflows that quickly convert collected points and line information into digital drawings.

First, export the survey points recorded on the rover’s data collector. Typical formats are CSV or TXT point lists, or directly CAD-compatible DXF/DWG files. Using office software such as Trimble Business Center or Leica Infinity, import RTK observation data, perform any coordinate transformations or averaging, and plot them into CAD drawings. If points have codes or attributes, the software can automatically symbolize them and connect lines (generate breaklines), enabling automatic base-map creation.

In CAD integration, unifying the coordinate reference between fieldwork and drawings is critical. If you surveyed in a predefined coordinate system, the exported coordinates fit directly onto design drawings. For example, if RTK surveying used a state plane coordinate system, the CAD drawings provided to engineers are created in the same state plane coordinates, preventing discrepancies downstream. If the surveyed data need to be presented in a different coordinate system, use office software coordinate transformation tools. U.S. projects often define a common coordinate reference early to ensure data interoperability among design and construction stakeholders.

In actual drawing production, generate contours from RTK-derived points, depict road centerlines and structure layouts, and more. When 3D data are available, use them for longitudinal and cross-section drawings and earthwork volume calculations. Increasingly, RTK-referenced point clouds from terrestrial scanners or UAVs are used to build detailed georeferenced 3D models. In any case, the ability to import high-precision RTK data into CAD/GIS quickly streamlines processes from design through construction.

U.S. Accuracy Standards and Data Submission Formats

Survey deliverables in the U.S. require certain accuracy standards and submission formats depending on the project and purpose. Typical RTK-derived accuracy is about ±1-2 cm (±0.4-0.8 in) horizontally and ±3-5 cm (±1.2-2.0 in) vertically (all at approximately 95% confidence). However, this varies with distance from the base station, satellite geometry, observation time, and other factors. For high-accuracy public surveys (for example, interstate highway surveys or critical infrastructure monitoring), RTK may be supplemented with static observations and rigorous network adjustment to achieve greater precision. For many construction and field surveys where tolerances of a few centimeters are acceptable, RTK accuracy suffices and its real-time efficiency is preferred.

The U.S. geodetic reference commonly used has been NAD83 for horizontal positions and NAVD88 for heights. Plans to replace these with new reference frames after 2025 are underway, but at the field level NAD83 state plane coordinates and NAVD88 elevations remain prevalent. Accordingly, RTK survey results are typically reported and recorded in these datums. For example: "In state plane coordinate zone ○○, a point’s coordinates are N=... m, E=... m, elevation=... m (NAVD88)." Deliverables usually include a report listing observed control points and survey points with coordinates, along with descriptions of accuracy (estimated errors and comparisons with control points).

Data submission formats depend on client requirements, but electronic data delivery is now standard. Deliver CAD drawings (DWG/DXF), GIS data (Shapefile/GeoJSON), or simple coordinate tables (CSV/Excel). Public contracts may mandate digital submissions alongside paper drawings and documentation. When new control points are established, results may be registered in state geodetic data repositories or reported to NGS for public release. For example, points determined via OPUS can be shared via the OPUS website, allowing others to use those points in the future; such open data practices are growing.

In summary, the U.S. approach to RTK surveying emphasizes selecting appropriate methods to meet required accuracy and delivering results in formats clear to recipients. Providing high-accuracy, consistent survey data in appropriate formats ensures reliability and efficiency for subsequent design and construction phases.

Spread of Mobile RTK and New Surveying Methods

Recently, due to miniaturization and smart device integration, mobile RTK has rapidly spread in the RTK surveying field. Traditionally, teams used stationary, expensive receivers and dedicated controllers with two to three crew members; now compact receivers that fit in one hand and tablet terminals enable one-person surveys. In the U.S., where labor shortages are increasing, such solutions that reduce labor while maintaining accuracy are attracting attention.

Key technologies for mobile RTK are integration with smartphones or tablets and cloud services. High-precision GNSS receivers connect to mobile devices via Bluetooth and surveying is performed with intuitive dedicated apps. General-purpose mobile devices are easier to handle than traditional controllers, and internet connectivity simplifies immediate cloud upload and stakeholder sharing of field data. For example, mobile RTK is powerful for capturing geotagged photos of damage at disaster sites and sharing position data to the cloud. In the U.S., one-person GNSS systems were deployed after hurricanes to rapidly assess damage, significantly shortening recovery planning time.

Concrete benefits of one-person surveying include dramatic reductions in work time and labor costs. Tasks that previously required two people a full day have been completed by one person in a few hours after mobile RTK adoption, yielding over 70% productivity improvements in some cases. Compared to multi-person layout tasks, solo work reduces communication errors and enables faster, accurate surveys. Solo operation also increases staffing flexibility and improves site safety by reducing interference with other heavy equipment.

With the spread of mobile RTK, single-receiver methods and shared infrastructure use have advanced. Single-receiver approaches include PPP (Precise Point Positioning) and augmentation services via satellite communications. These provide global, real-time corrections for satellite orbit and clock errors and ionospheric delays, enabling positioning without regional reference stations. Services like Trimble RTX or StarFire can provide centimeter-level positioning over wide areas with dedicated receivers. PPP typically has longer convergence times but is valuable where reference networks are unavailable, such as offshore, islands, or mountainous regions.

Shared infrastructure, represented by network RTK, lets multiple users share correction sources. Using state or regional RTK networks removes the need for each survey team to set up a base station every time, improving overall efficiency. Many U.S. surveyors and technicians leverage shared infrastructure to reduce initial equipment investment while conducting high-precision surveys. However, shared infrastructure depends on communications and service operators, so practical risk management includes backup plans (operating your own base station or switching providers) for service interruptions.

Thus, with the spread of mobile RTK and technological advances, RTK surveying is shifting from specialized team-based work to an everyday tool usable by many. Japan is seeing similar trends, with the Ministry of Land, Infrastructure, Transport and Tourism promoting simplified ICT construction, and smartphone–GNSS combined one-person surveying is expected to become standard.

RTK Easily Adoptable in Japan: LRTK Phone and Its Technology

Finally, focusing on Japan, LRTK Phone has emerged as a solution that makes RTK technology more accessible. LRTK Phone is a small, high-precision GNSS receiver attachable to a smartphone. Weighing about 165 g and roughly the size of a smartphone, it delivers centimeter-level real-time positioning and works by attaching to the back of an iPhone and linking with a dedicated app to enable high-precision surveys by a single operator.

The LRTK system’s feature is that hardware, software, and cloud services are integrated to complete the surveying workflow. Position data obtained by the LRTK Phone receiver are recorded in the LRTK app on the smartphone and can be combined with photos or AR verification on site. Recorded data synchronize instantly to the cloud (LRTK Cloud), allowing office-based 3D display, export to drawings, and data sharing. Historically, processing and sharing high-precision survey data required specialized software and procedures, but LRTK integrates these on a single platform for seamless workflows.

Technically, LRTK Phone is optimized for Japan’s positioning infrastructure. For example, it supports the Quasi-Zenith Satellite System Michibiki’s centimeter-class augmentation service (CLAS), allowing reception of correction information directly from satellites and continuation of RTK positioning in areas without cellular coverage such as mountainous regions. The built-in battery runs for about 6 hours and supports USB power, enabling extended field operations. When mounted on a dedicated telescopic pole, it allows stable point observations like conventional surveying instruments, and height offsets are easily compensated within the app.

Mobile RTK solutions like LRTK Phone lower the barriers to RTK adoption in Japanese surveying and construction sites. In Fukui City, LRTK Phone was used in disaster recovery surveys, enabling faster damage assessment and cost reduction compared to traditional approaches. Tasks previously outsourced to specialized survey companies can now be completed quickly and accurately in-house, accelerating decision-making. Such success stories have increased interest among municipalities and construction firms wanting to adopt the technology.

The standard RTK workflow developed in the U.S. is technically feasible in Japan, and LRTK Phone serves as an innovative bridge. For surveying professionals, RTK is no longer a specialized technique but is becoming a foundational, everyday tool. Going forward, actively adopting advanced RTK technologies like LRTK Phone will improve work efficiency and the quality of deliverables.