Table of Contents

• What is RTK positioning?

• Differences between Fix/Float/Single (no RTK)

• Main causes why RTK won't Fix

• Countermeasures when RTK won't Fix

• Simple surveying with LRTK

• FAQ

What is RTK positioning?

RTK positioning (real-time kinematic) is a technique that uses GNSS satellites to perform high-precision positioning in real time. Ordinary standalone positioning typically has errors of several meters, but RTK corrects errors through relative positioning between a base station (reference station) and a rover, achieving centimeter-level accuracy. Especially when it reaches the state called a Fix solution, positional reliability improves dramatically, greatly increasing work efficiency in surveying and construction sites. RTK is also applied to drone surveying and high-precision positioning for autonomous vehicles, and is attracting attention as a foundational technology for obtaining accurate location information in real time.

However, beginners attempting RTK positioning often encounter hurdles such as “it rarely Fixes” or “the accuracy isn’t achieved.” RTK is a delicate technology and is affected by many factors such as the surrounding environment and equipment settings. This article explains, from the basics and in an easy-to-understand way, the reasons why a Fix solution cannot be obtained in RTK and the solutions for them.

Differences between Fix/Float/Single (no RTK)

RTK positioning has several solution types depending on positioning accuracy. Here we explain the representative differences among Fix solution, Float solution, and Single positioning.

• Fix solution (fixed solution): A solution obtained by resolving the integer ambiguity from data with the base station. Simply put, this is the state where the number of carrier wavelengths from the satellite signals can be decoded exactly as integers, and errors are suppressed to within a few centimeters. This is the highest-accuracy state RTK aims for.

• Float solution (floating solution): A provisional position computed while the integer ambiguity remains unresolved. Compared to Fix, the error is larger, remaining on the order of several tens of centimeters to about 1 m. The position values are unstable and drift over time, hence called a Float solution. Early after starting RTK or in poor environments, a Float solution often occurs.

• Single positioning (standalone positioning): Normal GNSS positioning without corrections from a base station. It may simply be displayed as SINGLE or DGNSS. Accuracy is low—on the order of several meters—and indicates that high-precision RTK positioning is not being performed. This occurs when base station data cannot be received or when the receiver is not in RTK mode. For example, code-based positioning via satellite-based augmentation systems (SBAS) such as DGNSS offers accuracy at best around 1–3 m, which is orders of magnitude worse than RTK Fix solutions.

Whether you are positioned with a Fix solution is an important point for judging RTK quality. Always check displays like “Fix,” “Float,” or “Single” on surveying apps or receiver status screens, and maintaining the Fix state as much as possible is the key to high-precision positioning.

Main causes why RTK won't Fix

When RTK positioning does not readily produce a Fix solution (won’t Fix), several typical causes can be considered. Below are the main factors summarized.

• Insufficient satellite count or poor satellite geometry: If the number of available GNSS satellites is low or they are clustered in part of the sky, positioning accuracy deteriorates and a Fix solution becomes hard to obtain. Poor satellite geometry worsens geometric dilution of precision (DOP), making it difficult to stably solve the integer ambiguities. For high-precision 3D positioning, it is generally necessary to stably track five or more satellites; if observed satellites are few, the information required for Fix will be lacking.

• Obstructions and multipath around the site: In environments where sky visibility is blocked by buildings, trees, etc., satellite signals cannot be sufficiently received. Multipath (signal reflections/interference) from building walls or the ground is also a major enemy. When these degrade the signal, the RTK engine cannot perform accurate calculations and Fix may not occur.

• Distance from the base station is too great: If you are too far from your own base station or from the reference station of a network RTK service, error factors between the stations (such as ionospheric delay) can differ greatly and corrections become less effective. Generally, a longer distance to the reference station (the baseline length) can cause longer times to achieve Fix or unstable Fix. (In some cases, Fix can be obtained even when more than 50 km apart, but stability is significantly reduced.)

• Correction data not being received: Correction data from the base station is the lifeline of RTK. If an NTRIP connection via the internet is down or the base station data is not being distributed, Fix cannot be achieved. Even if data is being received, if the type of correction data does not match (for example, using multi-frequency data with a single-frequency receiver), or if the base station coordinate reference frame does not match the rover’s, the solution may not converge and Fix will not be reached.

• Strong RF interference or noise: Near strong radio sources such as directly under high-voltage power lines or close to radio stations, GNSS reception is subject to interference. When noise is present in the signal, positioning accuracy can deteriorate severely and may not improve from Float. For example, construction radios or Wi‑Fi routers operating nearby can introduce noise.

• Equipment configuration errors or hardware faults: If GNSS receiver or software settings are incorrect, proper RTK processing will not occur. For instance, if the rover is not set to RTK mode or the base station coordinates are misconfigured, Fix cannot be obtained. Also consider hardware issues such as broken antenna cables or poor connections that weaken signals.

• Problems in measurement procedure: Operation procedures for RTK also require attention. For example, if you start moving before the initial Fix is acquired while still in Float, you may not transition to Fix. Not allowing sufficient stationary time, or continuing measurements after Fix has been lost without doing anything, often results in collecting data without Fix.

Countermeasures when RTK won't Fix

If you recognize any of the causes above, taking the following countermeasures can increase the likelihood of obtaining a Fix solution.

• Improve satellite visibility and geometry: Choose environments and times when as many satellites as possible are visible. It is recommended to use GNSS planners to check satellite geometry in advance and perform positioning during times when satellite count is high and DOP values are favorable. If possible, use equipment that supports multi-GNSS (not just GPS but GLONASS, Galileo, Michibiki (QZSS), etc.) to increase the number of satellites and improve stability. Avoid setting the elevation mask angle too high in receiver settings (excluding low-elevation satellites); around 15° is a good balance.

• Avoid obstructions and mitigate multipath: Choose measurement locations that are as open as possible and ensure sky visibility. Simply moving away from buildings, trees, large vehicles, and other obstructions can increase the number of receivable satellites and make Fix easier. Laying a ground plane made of metal under the antenna to reduce ground reflections, or installing the antenna at a higher position to reduce the impact of nearby reflections, are also effective. Some high-quality GNSS antennas and receivers have multipath mitigation functions, but fundamentally you should aim to create an environment that avoids reflections. In severe multipath cases, moving just a few meters can often improve conditions.

• Keep the baseline length short: If you can set up your own base station, place it as close as possible to the measurement area. If using a network RTK, check whether the reference station providing the corrections is too far away. Switching to a nearer reference station data source or using a VRS (virtual reference station) service can effectively shorten the baseline. A shorter baseline reduces differential errors like ionospheric effects, shortening the time to Fix and improving stability.

• Check correction data reception status: Constantly monitor that NTRIP or other correction data communication is functioning. If using a mobile connection, place the device where reception is good and check for disconnections or delays. Verify in the receiver or app’s RTK status screen the “Age of Diff” (delay time of differential data) and the number of received messages to ensure corrections are being delivered in real time. If correction data lags by tens of seconds or more, maintaining a Fix becomes difficult, so receiving corrections as close to real time as possible is important. If no data is coming, reconfigure the connection or try restarting the mobile router. Also use correction formats appropriate for the receiver type (e.g., MSM4 for single-frequency receivers, MSM7 for multi-frequency). For your own base station, re-check that the configured base coordinates are correct and update them to an accurately known point if necessary.

• Avoid RF interference: During measurements, keep away from strong radio transmitters and other RF sources. It is prudent to avoid working directly under high-voltage transmission lines, near large radars, or near radio towers, as GNSS signals are more prone to noise there. If you must work in such environments, use high-performance antennas, noise filters, and keep distance from other devices to minimize impact. Also turn off unused wireless modules built into the receiver, such as Bluetooth, to avoid emitting unnecessary signals.

• Review settings and perform resets: Recheck RTK configuration parameters. Ensure the rover is truly in RTK mode, base station information (coordinates, mount point) is accurate, and unused radios are turned off. Performing a reset—such as reverting to single positioning mode and then switching back to RTK, or restarting the receiver and app—can be effective. Check antenna and cable connections for looseness or corrosion; reseating connectors can sometimes resolve the issue.

• Enforce correct measurement procedures: On-site, avoid rushing and make it a practice to begin measurements only after the Fix solution is stable. After powering on and starting positioning, remain stationary for several tens of seconds and wait for the first Fix. If you start moving before Fix is obtained, stop and wait for the receiver to re-establish Fix. If Fix is lost while surveying a moving object, stop at important points and wait to regain Fix before recording positions. If Fix simply cannot be obtained, consider restarting positioning (rebooting the receiver or correction connection). If that still fails, try relocating to a spot with a clearer sky. In many cases, moving the location is enough to obtain Fix. Always be mindful of whether you are recording in Fix, and do not leave data collection running when quality cannot be guaranteed.

Simple surveying with LRTK

Even with the countermeasures above, operating RTK stably in the field requires experience and know-how. For those attempting high-precision positioning for the first time, configuring equipment and adjusting the environment can be daunting. Using a solution called LRTK allows beginners to easily achieve high-precision surveying.

The LRTK series are small RTK-GNSS receivers that attach to smartphones and are designed so users can achieve centimeter-level positioning without worrying about complex settings. Compared to conventional surveying GNSS equipment, they are compact and lightweight enough to fit in a pocket, reducing the burden of carrying gear to the field. With an intuitive dedicated smartphone app, setting correction information and starting positioning are completed with just a few taps after powering on. They can be used without deep GNSS knowledge, making them suitable for surveying beginners.

Yet their positioning accuracy is very high and can stably obtain Fix solutions. Multi-GNSS support allows solid satellite tracking even in urban or mountainous areas, and models that support the augmentation signal from Japan’s Quasi-Zenith Satellite System (CLAS) can maintain high accuracy even outside communication coverage. For example, averaging data from a static measurement with an LRTK terminal can reduce a position that would be off by several meters in standalone mode to within a few centimeters. Without complicated manual work or expert tuning, LRTK lets you start simple surveying on site immediately. Moreover, by using LRTK, tasks that formerly required specialized surveying teams—such as setting batter boards or as-built measurements—can be performed quickly by on-site personnel, enabling faster data sharing and improving efficiency and labor savings.

Making high-precision location information easy for anyone to handle is the concept behind LRTK. If RTK Fix issues are troubling you, leveraging such modern devices can help resolve problems smartly.

FAQ

Q. How long does it normally take for RTK to reach a Fix solution? A. In good conditions, Fix is often obtained within several tens of seconds to about one minute after starting reception. With proper initial setup and no obstructions, a fixed solution is acquired relatively quickly after satellites are captured. However, if satellite geometry is poor or the RF environment is bad, it can take several minutes or more, or Fix may never be obtained. If Fix does not occur for a long time, review the environment and settings.

Q. Can I use positioning results while still in a Float solution? A. While in a Float solution, positional accuracy is inferior and may include errors of several tens of centimeters or in some cases over 1 m. For surveying or precise positioning, this is generally insufficient. If rough position information is acceptable for your use, Float can be used, but for tasks requiring accuracy such as dimension control or boundary measurements, always obtain a Fix solution before using the data.

Q. Can a single-frequency GNSS receiver achieve Fix? A. Single-frequency receivers (L1 only) can achieve Fix in principle. However, compared to multi-frequency receivers, initialization can take longer and ionospheric errors may not be fully corrected, making Fix less stable. It is preferable to use a multi-frequency receiver, but if using a single-frequency unit, choose conditions with better sky visibility and allow more time for measurement. When using only single-frequency equipment, more careful operation is required, such as selecting times and environments with fewer error sources.

Q. Can RTK be used at sites far from the reference station? A. The farther you are from the reference station, the harder it is to maintain RTK accuracy. Ideally stay within about 10 km; beyond that, Fix acquisition tends to be slower and less stable. When using RTK at long distances, obtain nearby reference station data such as from continuously operating reference stations (CORS) operated by local governments or commercial VRS services. If you must operate tens of kilometers away, be aware that accuracy will decrease.

Q. Does bad weather (rain or snow) affect RTK positioning? A. RTK positioning is generally less affected by weather, and rain or light snow typically does not cause major accuracy differences. However, heavy rain or snow that wets or covers the antenna can reduce signal strength and make Fix more difficult. Extreme conditions like thunderstorms with lightning can temporarily degrade reception. Consider safety and avoid surveying in very severe weather.

Q. Can RTK be used indoors or inside tunnels? A. GNSS signals do not reach well inside buildings or underground, so RTK positioning is generally not possible indoors or in tunnels. In environments where roofs or walls completely block satellite view, satellite capture itself is difficult, let alone Fix. If high-precision indoor positioning is required, consider alternatives to GNSS such as total stations or local positioning systems.

Q. Can a Fix solution be maintained while surveying on the move? A. As long as speed is moderate and satellite visibility is maintained, continuous positioning maintaining a Fix solution while moving is possible. RTK is actually used for high-precision tracking on drones and vehicles. However, sudden attitude changes or high-speed movement that momentarily cause satellite loss can break Fix and revert to Float. For moving surveys, stop to regain Fix when necessary, or combine with an IMU (inertial measurement unit) to supplement positioning data.