RTK Base Station Placement: Best Practices to Maximize Accuracy

Table of Contents

• The role of RTK base stations and the importance of placement

• Best practices for placing base stations to maximize accuracy - 1. Install the base station at a known, precise coordinate - 2. Ensure open sky visibility (place it where the sky is open) - 3. Avoid multipath interference - 4. Keep the baseline distance short - 5. Securely fix the base station - 6. Optimize the communication environment - 7. Consider the surrounding environment and weather

• Recommended: simple surveying with LRTK

• FAQ

The role of RTK base stations and the importance of placement

RTK (Real Time Kinematic) surveying is a method that uses two GNSS receivers—a reference station (base station) and a rover—to correct positioning errors in real time and achieve centimeter-level (cm level accuracy (half-inch accuracy)) high accuracy. The base station should be installed at a point whose coordinates are already known precisely; it computes the discrepancy between the satellite signals it receives and the known coordinates to generate correction information. The rover observes at each point to be surveyed and applies the corrections sent from the base station, reducing standalone positioning errors that may be several meters down to within a few centimeters (cm level accuracy (half-inch accuracy)). In other words, the base station functions as the reference point that enables the rover to perform high-accuracy positioning.

However, depending on how and where the base station is installed, RTK's inherent accuracy may not be achieved, and significant positioning errors or rework may result. For example, field reports show cases where RTK survey results were off by tens of centimeters to several meters due to incorrect coordinate input for the base station or improper antenna placement. Errors originating from the base station as a reference point affect all points measured by the rover, so the impact is large and post hoc correction is difficult. Therefore, in RTK surveying, “installing the base station correctly” is the most critical point for ensuring accuracy.

Below, for beginners to intermediate users, we explain the best practices for choosing RTK base station locations. We will look concretely at the points you should keep in mind to maximize positioning accuracy when using RTK on construction sites, infrastructure inspections, disaster surveys, and similar applications.

Best practices for placing base stations to maximize accuracy

1. Install the base station at a known, precise coordinate

The fundamental prerequisite for RTK accuracy is that the base station’s position coordinates are accurate. It is ideal to place the base station at known control points established by national or municipal authorities (public survey control points or continuously operating reference stations) or at points that have been precisely surveyed in the past. If known points cannot be used, determine high-precision coordinates in advance by static surveying or PPP (Precise Point Positioning), and operate that location as a temporary reference point. When absolute accuracy is required in a public coordinate system, aligning to the reference frame is essential.

Also, when entering or setting the base station’s coordinates into equipment, be careful not to mix up datums or coordinate systems. For example, selecting the wrong zone number in Japan’s plane rectangular coordinate system or confusing the World Geodetic System (WGS-84) with the Japanese Geodetic Datum (JGD) can lead to serious errors where all measured points are off by tens of meters. Double-check coordinate digits and signs, and if possible have another operator cross-check them. Antenna height input is also often overlooked: when installing the base station antenna on a tripod, accurately measure the height from the antenna reference point to the survey reference point and set it correctly in the controller.

Furthermore, if you are installing at a site for the first time, validating the base station setup with a test measurement is effective. After installing the base station, use the rover to measure nearby known points or existing stakes to confirm that the coordinates match. If discrepancies are found, correcting them before starting work minimizes impact. As described above, ensuring the accuracy of the base station’s location itself is the primary best practice for guaranteeing RTK surveying accuracy.

2. Ensure open sky visibility (place it where the sky is open)

Install the base station antenna in a location with an open view of the sky. GNSS signals from satellites are vulnerable to obstructions such as buildings and trees; poor sky visibility reduces the number of receivable satellites and degrades the satellite geometry, leading to reduced accuracy or delayed Fix acquisition. Ideally, choose a location with a view to the horizon in all directions (360°), but in urban sites or shadowed mountain areas this may be unavoidable. Even in such cases, it is important to orient the antenna toward directions with the widest possible sky view. As a general guideline, select a location with no obstructions within the elevation angle range above 15°.

If a rooftop of a site office or a high location is available, mounting the base station antenna at height greatly improves surrounding visibility. Conversely, avoid placing the antenna near ground level where nearby vehicles or workers can block signals. In forests or cityscapes, some low-elevation satellites may be unreceivable; check satellite geometry during planning and do not over-rely on satellites in unfavorable directions. Also, using multi-GNSS-capable receivers (tracking GPS as well as GLONASS, Galileo, QZSS, etc.) helps secure more usable satellites even with some sky blockage, which aids in maintaining stable positioning accuracy.

3. Avoid multipath interference

Measures against errors caused by surrounding reflectors (multipath) are indispensable. Multipath error occurs when satellite radio waves reflect off the ground or structures and reach the antenna via a longer path; because reflected waves arrive delayed relative to direct waves, the receiver may compute the distance as longer than it actually is, causing position errors. When installing the base station, choose a spot without strong reflectors near the antenna. Typical reflectors include water surfaces, metal surfaces, glass-clad buildings, and large vehicles. Be cautious if puddles, sea or river surfaces, metal fences, or construction vehicle beds that reflect radio waves like mirrors are nearby.

If reflectors cannot be entirely avoided, consider several countermeasures. One is attaching a ground plane (conductive reflector) to the receiving antenna. Placing a disk-shaped ground plane beneath the antenna cancels unwanted reflections from the ground direction and improves reception accuracy. Also, keep the area around the base station antenna tidy: do not park survey vehicles or heavy machinery next to the antenna, and move metal equipment boxes away to reduce extra reflections. In difficult environments, consider using a high-performance choke ring antenna. A choke ring antenna has concentric metal rings around the receiving element and suppresses multipath waves. Implementing multipath countermeasures improves the purity of positioning signals around the base station and contributes to maintaining accuracy.

4. Keep the baseline distance short

Keep the distance (baseline length) between the base station and the rover as short as possible. RTK cancels errors by simultaneous observation at both stations, but if they are too far apart environmental factors like atmospheric errors differ and residual errors that cannot be corrected increase. Generally, errors can be considered common over distances on the order of a few kilometers, so high accuracy is easier to maintain; however, beyond several tens of kilometers errors gradually increase, Fix determination can take longer, and accuracy can become unstable. Many high-precision GNSS receivers are specified like “horizontal accuracy: 8 mm (0.31 in) + 1 ppm” (1 ppm means about 1 mm of added error per 1 km of baseline length). From this value, you can see that for every 1 km the rover moves away, about 1 mm (0.04 in) of error is added, so positioning accuracy theoretically deteriorates with increasing distance.

Therefore, in RTK surveying, it is desirable to install the base station as close as possible to the work area—ideally on-site or within a few kilometers. For very large project sites where coverage of the entire area is required, consider adding base stations or relocating them as needed. If long distances are unavoidable, make use of regional continuously operating reference station networks (CORS) or network RTK services such as VRS to virtually shorten the baseline. In any case, keep in mind the principle that “the farther from the base station, the lower the accuracy,” and aim for positioning at the shortest practical distance.

5. Securely fix the base station

It is also important to secure base station equipment so it does not move. Often overlooked, even slight movement or tilt of the antenna is a source of error in high-precision positioning. If the base station antenna falls over or its position shifts during surveying, all results will be affected immediately. Therefore, always install the base station on a stable location. When using a tripod, fully extend the legs and anchor the spikes into the ground. If the surface is slippery like concrete, place the tripod feet on an anti-slip mat or hang a weight to prevent overturning from vibration or gusts. When fixing poles on rooftops, tighten the fasteners and check for any looseness. Use the antenna bubble level to level the antenna accurately and set it plumb; antenna tilt shifts the phase center horizontally.

Especially for long-duration surveys, equipment may warp gradually due to sun exposure or wind pressure. If possible, check the base station antenna status periodically during surveying and re-set it immediately if needed. Also clearly mark the base station location for safety; for example, use barrier tape or cones to prevent workers from accidentally kicking or moving a tripod, and place warning signs. Stable base station installation is the foundation that supports the reliability of RTK surveying.

6. Optimize the communication environment

Stable communication of correction data from the base station to the rover is also a condition for maintaining high accuracy. If communication is lost, RTK cannot maintain a fixed solution and positioning will revert to float solutions or standalone positioning. Correction data is mainly transmitted via low-power radio or UHF radio waves, or via the Internet (Ntrip over mobile networks); in any case, pay attention to optimizing the communication environment.

When using radios, mount the base station’s radio antenna as high as possible to secure line-of-sight to the rover. Low placement can cause radio blockage by terrain or structures and severely limit range. For unlicensed small radios (output 1 W or less), the line-of-sight range is roughly 1～2 km. For wider coverage, consider installing relay antennas or switching to digital simple radios or LTE modems. Also, if many devices operate on the same frequency band at the site, radio interference may occur. If correction reception is unstable, try changing the radio channel, slightly adjusting antenna positions, or switching to another communication method.

When using mobile-network-based services like Ntrip, ensure the base station has a stable Internet connection. In mountainous or out-of-coverage areas, a mobile router may lose signal and stop sending corrections, so check service availability in advance. Consider satellite communication terminals or PPK operation for offline situations. Whatever communication method you use, always monitor the rover’s RTK Fix status during surveying and do not continue measuring if corrections cannot be received. Detect and eliminate communication issues and resume work only after regaining Fix to avoid unnoticed accuracy degradation.

7. Consider the surrounding environment and weather

Finally, be mindful of the surrounding environment and weather conditions related to base station placement. For example, powerful radio-emitting machinery or power lines near the base station antenna can adversely affect GNSS reception. Avoid places near high-voltage lines, radar equipment, or large radio transmitters where possible, and monitor positioning stability closely if unavoidable.

Also pay attention to rapid weather changes. During heavy rain or lightning, not only does positioning accuracy degrade but the risk of equipment damage increases, so prioritize safety and suspend operations if necessary. Heavy rain can attenuate GNSS signals, making a Fix difficult to obtain, and lightning strikes on the base station antenna can damage equipment and threaten lives. For long-term outdoor operation, implement basic lightning protection measures when possible (e.g., choose locations near lightning rods when installing at height, disconnect cables when thunderstorms approach). Protect equipment from overheating in direct sunlight and from battery performance degradation in extreme cold; provide sunshades, insulation, or spare power as needed.

Additionally, on sites where work vehicles and heavy equipment move frequently near the base station, pay attention to vibration effects and physical contact. If excavation or blasting that causes strong vibrations will occur near the base station, evaluate the impact on positioning and consider temporarily suspending surveying. In summary, pre-check all environmental factors around the base station and reduce risks to continue high-accuracy positioning.

Recommended: simple surveying with LRTK

So far we have introduced best practices for RTK base station placement. There are many practical points, and some readers may feel “RTK surveying seems cumbersome.” Indeed, traditional RTK operation requires various preparatory tasks such as base station setup and environmental adjustments before surveying can begin. However, in recent years solutions have emerged that significantly reduce the effort and risk of base station setup.

A representative example is the new RTK system called “LRTK.” LRTK is a solution that combines a compact high-performance GNSS receiver with cloud services, requiring no complex wiring or cumbersome settings and enabling anyone to perform intuitive centimeter-level (cm level accuracy (half-inch accuracy)) positioning. Survey data and photos from the field are automatically shared to the cloud, eliminating worries about forgetting or losing data. LRTK also supports network RTK (Ntrip), so as long as there is mobile network coverage, high-precision positioning is possible without preparing a dedicated base station. This means you do not have to worry about the baseline distance issues described above, allowing flexible use from small rural sites to wide-area infrastructure inspections.

Where traditional RTK surveying was once expensive and required expertise, LRTK has rapidly simplified and reduced costs. If site supervisors and workers can each easily perform centimeter-level (cm level accuracy (half-inch accuracy)) surveying, there is no need to wait for a surveying team, and on-site productivity will improve dramatically. Unique use cases have already appeared, such as workers wearing LRTK devices on helmets for continuous positioning while walking, and the style of surveying itself is changing.

Of course, it goes without saying that it is important to understand the fundamentals while using technology. If you understand the base station placement points explained in this article, you can use the latest tools such as LRTK with confidence and a grasp of the underlying principles. If you are considering improving RTK surveying efficiency, try simple surveying with LRTK. A workflow that is not tied to base station installation can contribute to both productivity and accuracy improvements on site.

FAQ

Q1. Must I always install a base station for RTK surveying? A1. It depends on the site. If there are nearby public continuously operating reference stations or commercial network RTK correction services (such as VRS) available, the rover alone can achieve centimeter-level (cm level accuracy (half-inch accuracy)) positioning without the user installing a base station. However, this requires communication and may incur service fees. In remote mountainous areas or islands outside communication coverage, you will need to set up your own base station. Recently, solutions like LRTK that allow base-station-less positioning have appeared, but base stations are not entirely unnecessary; decide based on site conditions.

Q2. Should I install the base station antenna in exactly the same place each time? A2. During a project period, it is desirable to install it at the same known point. If surveying continues at the same site, fixing the base station position keeps daily measurements consistent and reduces error factors. If you must move the base station from day to day, be sure to install it based on known point coordinates and check for discrepancies with past data. For short-term work, leaving a simple benchmark to reproduce the same location is also effective.

Q3. How far from the base station does accuracy deteriorate? A3. As a general guideline, RTK accuracy and Fix acquisition speed begin to decline gradually when the distance from the base station exceeds about 10 km. Distances of a few kilometers are usually fine for centimeter-level (cm level accuracy (half-inch accuracy)) results, but at 20 km away getting a fixed solution can become difficult. For high-precision needs, place the base station within about 5–10 km if possible, or cover wide-area surveys with network RTK services or multiple base stations. Note that error increase with distance is gradual; for example, at 5 km separation the theoretical added error is about 5 mm (0.20 in), but environmental factors can make it worse.

Q4. If the base station location is constrained and visibility is poor, what should I do? A4. If you must operate in a location with poor visibility, there are several measures. First, if possible mount the base station antenna on a roof or pole to improve visibility. Use multi-GNSS receivers to increase the number of usable satellites. If satellites cannot be reliably tracked, consider short-term static averaging or alternative measurements with a total station. As a last resort, switch to post-processing positioning (PPK) and correct the data later.

Q5. Does using LRTK really make base stations unnecessary? A5. LRTK supports network RTK, so where mobile communication is available you can achieve high-precision positioning without setting up a dedicated base station. LRTK receivers obtain correction information via the Internet, so users do not need to operate their own base station. However, where communication does not reach, traditional base station operation may still be necessary. LRTK devices can also be used in base station mode when needed. In other words, you can normally perform convenient base-station-less positioning, and when communication is unavailable, use the LRTK device itself as a base station—this flexible approach is possible. In any case, LRTK has greatly reduced the burden of base station setup, and adoption is expanding across many sites. Consider applying it to your surveying operations.