7 Ways to Deal with RTK Float Not Fixing — Improving Reception Failures

In RTK (Real-Time Kinematic) positioning, you want to obtain a "Fix solution" if possible to achieve centimeter-level accuracy. However, in the field you often encounter situations where the solution remains a "Float solution" and never becomes Fix, or correction information is not reflected and you cannot escape a standalone "Single solution (no RTK state)". For tasks that require high-precision positioning, remaining at Float is insufficient, so it is important to quickly transition to Fix.

Fix means that RTK has removed inter-satellite error factors and correctly resolved the integer biases (ambiguities). Position accuracy is generally within about ± a few centimeters, providing reliability sufficient for precise positioning and surveying. On the other hand, Float is an intermediate state in which correction data is being received but the ambiguity solution has not converged; accuracy is typically about ±0.5–1 m (±1.6–3.3 ft). In other words, Float alone has too large an error for precise positioning. Under normal conditions, if things are favorable, Fix is usually achieved within several tens of seconds to a few minutes after starting RTK. However, if Fix is not achieved after more than 5 minutes, it is likely that some cause is preventing convergence.

So, when RTK does not progress from Float to Fix, what should you check and how should you respond? This article introduces seven points to review and countermeasures to improve reception failures when RTK does not Fix. Please use them for on-site troubleshooting.

Table of contents

• Countermeasure 1: Check the number and geometry of satellites in use

• Countermeasure 2: Improve the positioning environment (obstructions and multipath)

• Countermeasure 3: Review the base station setup and coordinates

• Countermeasure 4: Reduce the distance to the base station (baseline length)

• Countermeasure 5: Unify GNSS settings (satellite systems and frequency consistency)

• Countermeasure 6: Check correction data reception and the communications environment

• Countermeasure 7: Reconfirm GNSS equipment hardware and software settings

• Simple high-precision positioning solution using LRTK

Countermeasure 1: Check the number and geometry of satellites in use

First, pay attention to the number of satellites available and their sky geometry. For RTK, a guideline for obtaining a Fix solution is that there are at least five satellites being commonly tracked by both the base and rover. With around four satellites, three-dimensional positioning is barely possible, but achieving a fixed solution is difficult. The balance of satellite distribution in the sky (geometry) is also important. If satellites are biased in a particular direction, the geometry worsens and positioning accuracy decreases. If satellites are distributed evenly across the sky, the DOP value (dilution of precision) is kept low, making Fix more likely.

As a countermeasure, check the number of satellites currently being tracked and the DOP value on the receiver or app status screen. If the required number of satellites cannot be secured, try shifting the time of observation. GNSS satellite geometry changes over time, so selecting a time with good satellite geometry (low DOP) can increase the likelihood of achieving Fix more quickly. Also inspect whether the elevation mask setting in the receiver is set too high. For example, setting the elevation mask around 15° allows the use of low-elevation satellites to some extent, balancing satellite availability and accuracy. Furthermore, with modern multi-GNSS receivers you can use GPS, GLONASS, Galileo, QZSS (Michibiki), etc., simultaneously and may track more than 10 satellites. Enabling all available satellite systems to maximize the common observations can improve the Fix rate.

Countermeasure 2: Improve the positioning environment (obstructions and multipath)

The environment around the receiving antenna is another major factor preventing Fix. In locations with a narrow view of the sky, you cannot secure enough satellites and Float is likely to persist. In shadows of buildings, near forests, indoors, or inside tunnels, satellite signals are blocked and reception strength weakens, often leading to insufficient observation data and a prolonged inability to reach Fix. Nearby tall building facades, metal fences, or large vehicles can reflect satellite radio waves so they reach the antenna by incorrect paths. Such multipath errors destabilize the solution and hinder obtaining a Fix.

As a countermeasure, it is basic to perform positioning in as open an area as possible. If the measurement point is surrounded by buildings or trees, try moving the antenna position a few meters toward a spot with a view of the sky. That alone can increase the number of received satellites and lead to Fix. If you must survey in an obstructed area, mounting the antenna as high as possible is effective. Raising it on a tripod or pole to avoid surrounding obstructions improves signal reception. Another method is to obtain a Fix once at a location with a clear view and then slowly move to the target point. Some receivers can maintain Fix for a short time even if the environment degrades slightly after initial Fix.

Multipath countermeasures are also important. If possible, attach a ground plane (conductive plate) to the antenna to block reflections from below. Reducing reflections from the ground or vehicles directly beneath the antenna can improve positional stability. High-quality antennas and receivers may have internal multipath mitigation, but the basic principle is to create an environment that avoids reflections. Also check for strong radio equipment or high-voltage lines nearby. Strong electromagnetic interference can introduce noise into GNSS signals and inhibit Fix. If such equipment is present, consider temporarily stopping it during positioning or fitting the antenna with a noise filter to improve the radio environment.

Countermeasure 3: Review the base station setup and coordinates

RTK positioning relies on the rover performing corrections based on the accurate position of the base station. Therefore, if there is a problem on the base side, the rover will never obtain a Fix no matter how long it waits. If you operate your own base station, first check the base station coordinate settings. It is important to set coordinates with small errors; if possible, perform about an hour of averaged observation beforehand or calibrate at a known point to obtain coordinates close to the true value. If you are using provisional coordinates obtained from a short observation, they may contain significant biases. Setting coordinates that are far from the actual position causes initial errors in RTK calculations, leading to longer convergence times or nonconvergence in resolving integer ambiguities. If the base station coordinates are off by tens of meters or more, the inconsistency with correction information will be too large and convergence to a fixed solution will be significantly delayed. Also check that the coordinate systems (datums) of the base and rover match. For example, if the base uses the old Japanese geodetic system while the rover operates in WGS84, the applied correction will produce an offset of tens of centimeters and prevent correct Fix. Use the same public coordinate system.

Next, review the base station antenna installation. Fix the base antenna in a stable place so it absolutely does not move. If the installation is loose and the antenna falls or its position shifts, RTK must restart from zero and the rover, even if nearly Fix, will revert to Float. Strong winds causing tilt are also problematic; secure the tripod or mount with brackets and place it where workers cannot inadvertently touch it. If the antenna has been moved, stop RTK and immediately reconfigure the base station coordinates. Also check the base station reception environment since it affects quality. Install the base station with as open a sky view as possible and away from reflective objects or obstructions. If the base station’s satellite set is small or has large errors, high-accuracy Fix cannot be obtained even if the rover’s environment is open. Also verify hardware issues such as power, antenna cables, and whether transmission has stopped.

Even when using public Continuously Operating Reference Stations (CORS) or third-party base station data, base-side problems can prevent Fix. If the provider’s observation environment is poor or the station is under maintenance and accuracy is degraded, there is little the user can do. In such cases, consider switching to another service or reconnecting after some time.

Countermeasure 4: Reduce the distance to the base station (baseline length)

A long distance between rover and base station can also prevent Fix. RTK correction works by canceling common errors between the base and rover, but as the baseline length increases, the differential of errors between the two points grows and the effectiveness of corrections diminishes. Error sources like ionospheric and tropospheric delays differ more with longer distances and cannot be canceled as common errors. As a result, integer-bias resolution becomes unstable and convergence to a fixed solution may take a very long time or remain Float indefinitely.

Generally, RTK is more stable and accurate with shorter baselines. As a practical guideline, a baseline within 10 km (6.2 mi) is desirable. Up to roughly 10 km (6.2 mi), most common errors between base and rover are canceled and centimeter-level accuracy (cm level accuracy, half-inch accuracy) can be obtained relatively easily. But at 20 km (12.4 mi) or 30 km (18.6 mi), residual errors that cannot be corrected accumulate and convergence becomes unstable. Depending on the environment and equipment, Fix may still be possible, but maintaining it requires caution. At distances over 50 km (31.1 mi), obtaining a fixed solution with conventional RTK becomes difficult.

As a countermeasure, try to shorten the distance to the base station as much as possible. If you operate your own base, review its placement so it is not too far from the rover’s work area. For wide-area sites, consider relocating the base station closer as needed. If using existing correction services, choose the nearest available base station or a virtual reference station (VRS) if selectable. When long distances are unavoidable, utilize multi-frequency-capable receivers. Dual-frequency L1/L2 receivers are better at compensating ionospheric errors over long baselines than single-frequency (L1-only) units, increasing the likelihood of achieving Fix. It is preferable that both base and rover support two or more frequencies; if one is single-frequency, set the other to L1-only correction mode or ideally upgrade both to dual-frequency equipment.

Also, when long-distance RTK is unavoidable, consider the time of day. Solar activity during daytime increases ionospheric disturbances, which especially affect long baselines. If you must perform measurements over tens of kilometers, aiming for nighttime to early morning—when the ionosphere is more stable—can increase success rates. For large distances where errors grow, consider switching from real-time RTK to non-real-time methods like static reference point observation or PPP (precise point positioning), which do not require real-time communications.

Countermeasure 5: Unify GNSS settings (satellite systems and frequency consistency)

If GNSS settings are inconsistent between base and rover, Fix may never be achieved. RTK calculations require both stations to use observations of the same satellites, so if one side has different settings, corrections will not be applied correctly. For example, if the base uses GPS+GLONASS but the rover has GLONASS disabled, GLONASS-derived corrections are ignored, reducing the number of effective satellites and making the solution less stable. Conversely, even if the rover is multi-GNSS capable, if the base station data contains only GPS and no other systems, the RTK becomes GPS-only and may remain Float under some conditions. In the settings screen, enable all available satellite systems (GPS, GLONASS, Galileo, BeiDou, QZSS, etc.) on both sides to maximize tracked satellites. Pay special attention to ensure GLONASS is not disabled on either side.

You must also align the frequency combinations used. If the base and rover use different frequencies, common observations cannot be taken and this will prevent Fix. If one unit is single-frequency, set the other to L1-only correction mode or, ideally, match both as dual-frequency receivers. Correction data format compatibility is also important. RTK typically uses RTCM messages, but certain output message types or versions from the base may not be interpretable by the rover. At minimum, confirm that base station coordinate information (e.g., RTCM 1005) and observation messages for each satellite system (e.g., 107x for GPS, 108x for GLONASS) are being transmitted and that the rover is not missing required data. Older receivers may not support the latest RTCM messages and may ignore some satellite data, causing failure to Fix. In that case, restrict the base station to compatible message types or update the receiver firmware to support newer messages.

If Fix still does not occur after reviewing these settings, try restarting the equipment. Software glitches can sometimes prevent setting changes from taking effect. Power off the entire RTK system (both base and rover), then power on the base first and reconnect; this can result in proper application of settings and attainment of Fix.

Countermeasure 6: Check correction data reception and the communications environment

RTK requires that correction data from the base station reach the rover for high-precision computation. If correction information is not being received, Fix will never be achieved. First, confirm via the device communication status that you are correctly receiving correction data. If the dedicated app or receiver shows “receiving correction data” or a communications icon, it is normal; if not connected, review NTRIP and other settings. If using network RTK over the Internet, check that a smartphone or router is online and that the mobile signal strength is sufficient. If you are out of coverage or tethering has been interrupted, corrections will not arrive and the receiver will revert to Float or Single. If necessary, move to a location with better signal or toggle airplane mode to reconnect. In mountainous areas with unstable coverage, consider alternative communications (e.g., using a different carrier’s SIM, or a mobile Wi-Fi router that supports other carriers).

For cases where correction data is not received, NTRIP connection mistakes are common. Mistyping the host name (IP), port number, mount point name, or username/password will prevent server connection. Re-check each item for typos or extra spaces. Deleting and re-entering settings can reveal mistakes. Pay attention to case sensitivity in IDs and passwords. If you use a virtual reference station (VRS) service, ensure the rover’s approximate position is being sent correctly. If the vehicle position was incorrectly registered during initial setup or position transmission is OFF, appropriate correction data may not be provided and Fix will be impossible.

If corrections are distributed via low-power radio or digital radio, check the radio line-of-sight and interference conditions. It is ideal that there be no obstacles between the base and rover antennas and that antennas are installed at sufficient height. Low-power radios have an effective range of about 1 km (0.6 mi), so beyond that corrections may not be received. Consider repeaters or switching to licensed high-power radios. Also, if other devices use the same frequency band nearby, data loss due to interference can occur. Change channels or pause the interfering equipment during positioning.

Even when communications are connected, intermittent loss of correction data makes maintaining Fix difficult. For example, if the base’s transmission interval is extremely long (e.g., sending only once every several tens of seconds), updates may lag and the rover can revert to Float. Frequent packet loss or CRC errors also cause missing required information and prevent convergence. If communication delay or data loss is suspected, try disconnecting and reconnecting or testing a different correction service. If possible, monitor values such as Age of Differential or the number of RTCM messages received on the rover to verify in real time that corrections are arriving.

Note that if a temporary communication interruption occurs, it is important not to panic and to wait a bit. Many GNSS receivers maintain positioning for several tens of seconds using internal prediction even when corrections cease; if communication resumes during that time, Fix may be regained. However, if disconnections are frequent, fundamentally improving communications or considering non-communication-dependent positioning methods (such as the satellite-based augmentation services described below) is advisable.

Countermeasure 7: Reconfirm GNSS equipment hardware and software settings

Finally, inspect the GNSS receiver and peripheral equipment themselves. Surprisingly, connection faults and setting mistakes are common causes of failure to Fix. First, if using an external antenna, check for loose cables or breaks. If the antenna connector is not firmly attached, signal reception can be severely reduced and positioning accuracy lost. If equipment that previously Fixes suddenly stops Fixing, suspect antenna cable faults or receiver hardware failure. In such suspected hardware-fault cases, try changing to another antenna, reseating the cable, or performing a reset to see if conditions improve.

Also check the smartphone or tablet app that interfaces with the GNSS receiver. Confirm that the positioning mode (kinematic or static) matches your operation, that you have not inadvertently disabled any satellite types, and that parameters have not been changed from defaults. For example, if surveying while moving but the receiver is set to static mode, the solution may become unstable; conversely, if performing static observations but using kinematic mode, you may get excessive noise. Switching to the appropriate mode can stabilize the solution. Some positioning software allows reloading base station information or reinitializing the system, which can lead to Fix, so try those options.

Review antenna mounting as well. Keep the antenna as level as possible and secure to prevent tilting. If tilted, the satellite signal reception pattern becomes biased and accuracy suffers. When mounted on poles or tripods, check level with a spirit level. If the antenna is mounted high, also ensure it is not swaying in strong winds; reinforce fixation with guy lines as needed to prevent vibrations from disturbing the solution.

As a basic step, restarting the GNSS equipment and app is often effective. Software glitches or insufficient memory can be resolved by rebooting. Power-cycle both base and rover and restart in sequence to see if this resolves the issue. Reconnecting after a restart can sometimes easily solve a problem that previously prevented Fix.

Simple high-precision positioning solution using LRTK

Above, we introduced seven main countermeasures when RTK remains Float and will not Fix. Still, in some field situations you may not be able to secure an ideal antenna location, cannot reduce the distance to the base over a wide site, or lack confidence in equipment settings due to limited technical knowledge. In such cases, a helpful high-precision positioning solution gaining attention is LRTK, a system consisting of a compact GNSS receiver and a smartphone app.

LRTK is a palm-sized, high-performance RTK-GNSS receiver designed to be attached to a smartphone or tablet (for example, an iPhone or iPad) to make centimeter-level positioning easy and reliable on site. Several features cover the factors that make Fix difficult from both hardware and software perspectives.

First, LRTK receivers support multi-GNSS and multi-frequency observations, capturing not only GPS but GLONASS, Galileo, BeiDou, and QZSS (Michibiki). Observing on L1/L2 dual frequencies improves removal of ionospheric errors, allowing stable positioning even in urban areas by ensuring sufficient satellite numbers. This prevents satellite shortages and accuracy degradation over long baselines, making Fix easier to obtain in a shorter time.

LRTK models also offer satellite-based augmentation reception. They can directly receive centimeter-class augmentation services (CLAS) broadcast by Japan’s QZSS, enabling centimeter-level positioning even in areas without RTK base stations, such as mountainous or overseas areas. The flexibility of maintaining high accuracy without real-time communications is a major advantage.

Furthermore, the smartphone integration provides an intuitive user interface. The dedicated app displays satellite reception status and correction data at a glance, enabling rapid identification of causes when Fix does not occur. Complex NTRIP setup is simplified by selecting pre-registered correction services, reducing input mistakes. Even users with limited expertise can operate intuitively, helping to reliably obtain Fix in the field.

By using LRTK, tasks that formerly required experience and trial-and-error for RTK positioning can be greatly simplified. For those troubled by RTK Float problems, LRTK can be a reliable ally. As a modern device that makes high-precision positioning easier, consider introducing LRTK in your field operations.