Why Won’t RTK Fix? The 5 Major Causes of Float/no RTK and Their Countermeasures

Table of Contents

• What Fix, Float, and no RTK mean in RTK positioning

• Cause 1: Poor satellite signal reception environment

• Cause 2: Base station setup or reference coordinate errors

• Cause 3: Distance to the base station is too long

• Cause 4: GNSS setting mismatches (satellites used or frequencies)

• Cause 5: Correction data not received / communication troubles

• What simplified surveying with LRTK is

• FAQ

In RTK (Real Time Kinematic) high-precision positioning, the ideal goal is to obtain a “Fix solution” and achieve centimeter-level accuracy. However, on real sites you often hear complaints that the system never achieves Fix and remains in a “Float solution,” or that corrections don’t take effect and it stays in a “no RTK (single)” state. For field workers and managers considering the introduction of surveying equipment, it is important to understand why RTK does not Fix and take measures accordingly. This article explains the five main causes why RTK fails to Fix and countermeasures for each. First, we’ll review the differences among Fix, Float, and no RTK states, then go through cause-specific remedies. At the end of the article we also introduce simplified surveying using LRTK as a practical solution to these problems.

What Fix, Float, and no RTK mean in RTK positioning

First, let’s be clear on the meanings of the RTK positioning status indicators “Fix”, “Float”, and “Single (no RTK)”.

• Fix (fixed solution): The RTK solution has converged to integer ambiguity values. Phase differences between satellites that cause errors are reconciled, and high-quality corrections are being applied. Typically centimeter-level accuracy (within ±2 cm (±0.8 in)) is obtained, which is sufficient for surveying and precision construction. Achieving this Fix solution is the goal in RTK operation.

• Float (floating solution): Correction data are being received, but the solution has not yet reached integer ambiguity resolution. It is essentially an intermediate computed solution, also called a floating-point solution. Accuracy is submeter, generally around ±0.5–1 m (±1.6–3.3 ft), and it is less reliable than a fixed solution. For practical applications that tolerate some error—such as certain agricultural uses or navigation—Float may be usable, but for precise surveying it is insufficient.

• Single (single solution / no RTK): No corrections from a base station are being applied; this is a standalone GNSS solution. This is usually the position computed by the GNSS receiver itself and can have errors of several meters (± a few m to 10 m (32.8 ft)). It may be displayed as “no RTK” or “DGPS off.” Because RTK benefits are not realized, this state is not suitable for high-accuracy tasks.

Because accuracy differs greatly by status—centimeter-level for Fix, at best decimeter-level for Float, and meter-level for Single—situations that require high precision must move from Float or Single to Fix as quickly as possible. Normally, if the sky is open and a sufficient number of satellites are visible, it is common to enter Fix within a few tens of seconds to a few minutes after starting RTK. High-performance receivers and algorithms may achieve Fix in about 20 seconds when conditions are favorable. If Fix is not achieved after more than 5 minutes, something is likely preventing convergence. Check whether any of the causes described below apply and try appropriate countermeasures to see if the situation improves.

Cause 1: Poor satellite signal reception environment

In environments surrounded by buildings or trees, it becomes extremely difficult to obtain an RTK Fix. GNSS signals travel largely in straight lines and are easily blocked by obstacles, so when sky visibility is poor the number of receivable satellites decreases and signal strength weakens. Additionally, receiving signals reflected off metal or concrete surfaces causes multipath errors, which destabilize positioning solutions. Under such poor reception conditions, even if correction information arrives, the necessary observation data may be insufficient and the processing engine cannot converge the integer ambiguities. As a result, the solution may remain Float indefinitely or, in the worst case, corrections fail to apply and the solution stays Single.

Countermeasures: Antenna placement determines RTK quality. Operate the receiver in as open an area as possible to improve satellite visibility.

• Move to a location with an open sky: If your current measurement point is inside a garage, next to a grove, or in a building’s shadow, move to a wide spot with a clear view of the sky and re-measure. The more sky is visible in all directions, the more satellites you can capture, which significantly reduces time to Fix.

• Install the antenna properly: Place the GNSS antenna as high as possible and away from surrounding obstructions. Raising the antenna with a tripod or pole, for example to a roof or above obstacles, improves reception. Avoid placing the antenna directly on the ground or on a car hood; use a stable dedicated pole or magnetic mount. If there are strong reflectors nearby (large vehicle bodies, metal fences, etc.), try to relocate the antenna to increase separation.

• Acquire Fix before moving to the desired measurement spot: If you must measure a location surrounded by obstacles, rather than trying to get a Fix immediately at that spot, start RTK at a nearby open location to obtain Fix and then slowly move to the measurement point. Some receivers can maintain Fix for a short time even in poorer visibility once Fix has been obtained. Even if it drops to Float during movement, regaining satellite visibility increases the chance of returning to Fix.

Also pay attention to radio interference in addition to sky visibility. Strong local radio sources (e.g., construction communications equipment or high-voltage line apparatus) can disturb GNSS reception. If such sources are suspected near the site, measure during times when those devices are not in use or apply noise mitigation measures to the antenna.

Cause 2: Base station setup or reference coordinate errors

RTK relies on accurate base station coordinates to apply corrections to the rover. If there is any problem on the base station side, the rover may never obtain a Fix. A typical example is a base station coordinate input error. If the base station’s latitude, longitude, or height are set incorrectly or a provisional coordinate has a large error, the initial RTK solution may be biased and integer ambiguity resolution may take much longer or fail to converge. If the base station coordinate is off by tens of meters or more, the inconsistency with correction data can be so large that convergence to a fixed solution is significantly delayed.

Base station antenna installation errors are also problematic. If the base antenna is placed on an unstable spot and moves during observations or is tilted by strong wind, the base station cannot continue accurate observations. Naturally, corrections sent to the rover will be unstable, causing Fix to collapse or revert to Float. Moreover, if the environment where the base station is installed is poor (narrow sky, nearby tall buildings, etc.), the quality of the correction data will degrade. Even if the rover is in an open area, reliable Fix cannot be expected if the base station’s data cannot be trusted.

Countermeasures: If you operate your own base station, recheck the initial setup and installation environment.

• Measure the base station coordinates accurately: When installing a new base station, perform about an hour of averaged positioning or calibrate on a known control point to obtain coordinates as close to the true values as possible. If coordinates were obtained from a short observation, they may contain large errors—consider remeasuring or comparing with public control points. If installing on an existing reference point, be careful about coordinate system differences (e.g., global vs. local datum). Reconfirm there are no input mistakes and correct values if needed.

• Prevent movement of the base station antenna: After installation, ensure the antenna position is not changed. If it is knocked over or shifted, RTK must start over. Use fasteners or weights to stabilize the antenna and place it where workers won’t accidentally touch it. If it is moved, stop RTK immediately and reset the coordinates.

• Keep the base station reception environment good: As noted in Cause 1, satellite reception is also important for the base station. Install the base station where sky visibility is open and with minimal reflection and obstruction. If the base station sees few satellites, rover corrections will be limited. Inspect the base station antenna cable for breaks or looseness and ensure stable power supply.

If you use public online base station services or third-party base station data, Fix failures can also be due to problems on the provider side. For example, if the provider’s observation environment is poor or maintenance has degraded accuracy, there is little the user can do other than try another service or reconnect later. Also, when combining your own base station with external data, be careful about coordinate system mismatches (mixing local and global coordinate systems, etc.).

Cause 3: Distance to the base station is too long

If the distance (baseline length) between rover and base station is too long, RTK is less likely to Fix. RTK corrections rely on the base and rover sharing the same error sources so they can be canceled out; as distance increases, the errors experienced by the two points differ and the effectiveness of corrections decreases. In particular, ionospheric and tropospheric effects grow with distance and cannot be fully canceled over long baselines, making integer ambiguity resolution unstable. As a result, it may take a very long time to obtain a fixed solution or the solution may remain Float.

In general, RTK is more stable and accurate with shorter baselines. As a rule of thumb, practical operation prefers baselines within 10 km. Within about 10 km, most common errors between base and rover cancel out and centimeter-level accuracy can be relatively easily achieved. However, when distances extend to 20 km or 30 km, residual uncorrectable errors accumulate and convergence becomes unstable. With good algorithms and favorable conditions, Fix may still be achievable, but maintaining accuracy requires additional measures. At distances above about 50 km, obtaining a fixed solution with conventional RTK becomes difficult; in such cases consider satellite augmentation or network RTK solutions.

Countermeasures: If the baseline is excessively long, take steps to shorten it.

• Use the nearest possible base station: If you operate your own base, plan placement so it is not too far from the rover’s work area. For wide-area sites, consider relocating the base station as the work moves. If using a provider service, choose data from the closest base station or use VRS options if available.

• Use multi-frequency receivers for long distances: As baseline length increases, ionospheric errors become non-negligible. Receivers that observe multiple frequencies (L1, L2, L5) have an advantage. Dual-frequency or better RTK is more likely to obtain Fix over longer distances compared to single-frequency systems. For long baseline links, use dual-frequency or multi-frequency equipment on both ends when possible.

• Consider time of day and ionospheric activity: During times of high solar activity or daytime ionospheric disturbance, long-distance RTK becomes even harder. If you must survey across tens of kilometers, choose periods when ionospheric disturbance is minimal (generally night to early morning) to increase success rate. For long distances, also consider alternative methods such as control network measurements or PPP (precise point positioning) rather than conventional RTK.

Cause 4: GNSS setting mismatches (satellites used or frequencies)

If the satellites or signal settings used by the base and rover do not match, RTK will not Fix. RTK requires both ends to compute using observations of the same satellites. If one side uses GLONASS while the other does not, or frequency band settings differ, common observations cannot be obtained and corrections cannot be properly applied. For example, if the base tracks GPS+GLONASS but the rover is set to GPS only, GLONASS-derived corrections are ignored, reducing the number of effective satellites and making the solution less stable. Conversely, if the rover supports multi-GNSS but the base data contains only GPS, the RTK process is limited to GPS and may remain Float in some conditions.

Also be aware of incompatibility in correction data formats when combining older or mixed-brand equipment. RTK corrections typically use the RTCM standard, but depending on version and message types, the receiving equipment may not be able to interpret some transmitted information. If the base outputs additional messages for GLONASS or Galileo and the rover is not compatible, it cannot process those messages correctly, causing persistent Fix failures. Special correction signals such as Japan’s QZSS (Michibiki) augmentation may also require dedicated settings or compatible equipment.

Countermeasures: When deploying an RTK system, unify the base and rover settings.

• Use the same GNSS constellations on both ends: Enable all available systems (GPS, GLONASS, Galileo, BeiDou, QZSS, etc.) and maximize the number of commonly tracked satellites. Check the settings to ensure no constellation is disabled on either end. GLONASS is sometimes off by default, so pay particular attention. Using multi-GNSS receivers that can process multiple constellations simultaneously significantly improves Fix stability.

• Match frequency combinations: Confirm that base and rover use the same frequency bands (L1/L2, etc.). Dual-frequency receivers normally use both automatically, but if one side is single-frequency, the other must be set to L1-only correction mode (or, preferably, both upgraded to dual-frequency). In mixed environments, pay careful attention to mutual compatibility.

• Verify correction format compatibility: Check the RTCM message types output by the NTRIP service or base station software. At minimum, include base station coordinates (1005) and observation/ephemeris messages for each constellation (GPS: 107x, GLONASS: 108x, etc.). If the rover is an older model that cannot handle newer RTCM messages, some data may be missing and Fix may not be achieved. In such cases, change the base station’s output to compatible message types or update firmware.

If rechecking settings still fails to produce Fix, try restarting the equipment. Occasionally software glitches prevent proper data reflection. Reboot the RTK system in the order base station → rover, and settings may then take effect and allow Fix to be achieved.

Cause 5: Correction data not received / communication troubles

If the correction information from the base station is not being received, Fix will never be achieved. RTK requires continuous real-time transmission of correction data; if that communication is interrupted or misconfigured, the rover cannot escape standalone positioning. A common example is network issues when receiving corrections over the Internet via NTRIP. In mountainous areas mobile connectivity may be unstable, or tethering may be disabled on a smartphone, causing corrections to stop and the solution to revert to Float or Single. Incorrect NTRIP settings—such as host name, mount point, or login credentials—also often prevent a connection from being established. Similarly, when broadcasting corrections via low-power radio or digital radio, leaving the coverage area or experiencing interference will lead to missing corrections and inability to maintain an RTK solution.

Even if communications are connected, intermittent loss of correction data makes maintaining Fix difficult. For instance, if the base station’s broadcast interval is extremely long (e.g., only once every 30 seconds), the rover may drop back to Float between updates. Also, if communication is present but the data contain many errors (packet loss or CRC errors), the receiver cannot reconstruct the information needed for Fix calculations.

Countermeasures: Check whether correction data are arriving normally from communication status indicators. Many RTK-capable devices and apps display correction reception status, differential age, and base station latency numerically. If these are not updating or show errors, suspect communication problems.

• Verify Internet connectivity: If using NTRIP, check that the rover’s Internet device (smartphone, tablet, router) is reliably connected. If signal is weak, move slightly, toggle airplane mode on/off, or try basic network troubleshooting. In outdoor LTE-poor areas, consider using a different SIM or another carrier (dual-SIM routers that switch to the stronger line are convenient).

• Correct NTRIP settings: Hostname (or IP), port, mount point, username, and password must all be correct. Even one mistake prevents corrections from being received. Carefully review entries, paying attention to case sensitivity and stray spaces. Deleting and re-entering the settings sometimes reveals typing errors.

• For radio communications, ensure line-of-sight and address interference: If you use your own radio link, confirm antenna line-of-sight and placement. Install the base antenna as high as possible and avoid obstacles between base and rover. Low-power radios are effectively limited to about 1 km, so beyond that consider a repeater or switching to licensed higher-power radio. If other devices use the same frequency band and cause interference, change channels or eliminate nearby noise sources.

If corrections are temporarily cut, it’s also important to remain calm and wait briefly. Many GNSS receivers use internal prediction to maintain positioning for several tens of seconds after corrections stop; if communication is restored within that window, Fix may return. If communications frequently drop, take the above measures to stabilize them or consider alternative positioning methods that do not require real-time communication (for example, satellite-based augmentation services as discussed below).

What simplified surveying with LRTK is

So far we’ve reviewed the main causes and countermeasures for RTK failing to Fix. Still, in the field there are cases where you cannot move the antenna, distances are inevitably long, or operators lack the expertise to confidently configure settings. In such cases, our simplified surveying solution using LRTK can be helpful.

LRTK is a system composed of a compact high-performance RTK-GNSS receiver and a smartphone application, developed to make high-precision field positioning easier and more reliable. LRTK addresses the common causes of Fix failure both in hardware and software.

• Multi-GNSS and multi-frequency support for stable positioning: LRTK receivers support not only GPS but also GLONASS, Galileo, QZSS (Michibiki), and can perform dual-frequency L1/L2 observations. This ensures sufficient satellite availability even in urban areas, improves ionospheric error mitigation, and makes it easier to attain Fix in a shorter time.

• Support for CLAS augmentation signals: Some models can receive CLAS, the centimeter-level augmentation service from Japan’s QZSS, allowing centimeter-level positioning directly from satellites even where RTK base stations cannot be installed. This flexibility enables high accuracy in mountainous or out-of-coverage areas where conventional RTK is difficult, removing dependence on communication and baseline length.

• Easy operation via smartphone integration: A dedicated app provides intuitive management of base and rover settings and connection status. Satellite reception and correction data status are visible at a glance, making it easy to quickly identify causes when Fix doesn’t occur. Complex NTRIP configuration can be reduced to selecting a pre-registered server, greatly lowering the chance of setting errors. This usability enables field staff without specialized knowledge to operate correctly.

• Cloud integration and tilt correction: Positioning results can be synchronized to the cloud in real time, allowing data sharing and checks before returning to the office. Newer models include a tilt sensor in the receiver, automatically correcting for pole tilt to obtain accurate coordinates even when the pole is not perfectly vertical. This allows measurement in confined spots without losing points and improves work efficiency.

LRTK thus offers a unique solution that balances RTK accuracy and usability. It is designed to minimize the common “won’t Fix” troubles in the field and enable anyone to perform high-precision surveying easily. If you find yourself frequently struggling to achieve Fix with your current setup, consider switching to simplified surveying with LRTK—it can be a reliable partner that achieves stable Fix even under complex conditions.

FAQ

Q1. How much difference in accuracy is there between Fix and Float? A. As a general guideline, a Fix solution is typically within ± a few centimeters, while a Float solution can have errors of ± several tens of centimeters. In a no RTK (Single) state errors can be ± several meters or more. For example, in the LRTK system case, the accuracy targets are within 10 m (32.8 ft) in no RTK, within 1 m (3.3 ft) in Float, and within 2 cm (0.8 in) in Fix. Therefore, for tasks requiring precise positioning, Float or Single are insufficient and you should always obtain Fix before adopting the measured results.

Q2. How many satellites are needed at minimum to obtain an RTK Fix? A. The exact number depends on the algorithm, but generally five or more common observations are required. Four GPS satellites alone only enable standalone positioning and are not enough for an RTK fixed solution. If both base and rover track five satellites—and preferably six or more—the chance of Fix increases. Modern receivers supporting multi-GNSS can use 10–20 satellites simultaneously, reducing cases where insufficient satellite count prevents Fix. Satellite geometry is also important—if satellites are clustered in one part of the sky, even a large number may not yield good accuracy. Choosing a time when satellites are well distributed can be a shortcut to obtaining Fix.

Q3. How long does it normally take for RTK to first reach Fix? A. Under good conditions it often takes about 30 seconds to 2 minutes to reach Fix. If the sky is unobstructed and signals are stable, a receiver can fix within one minute after startup. Conversely, in poor environments or if base data reception is delayed, you may remain in Float for over 5 minutes. Once Fix is obtained and positioning continues, Fix is typically maintained unless communications fail or the environment changes suddenly. If Fix does not occur after 5 minutes, review settings and environment as discussed in this article; sometimes restarting the receiver or moving location is the fastest way to achieve Fix.

Q4. Do weather or time of day affect the ease of Fix? A. Weather itself (rain or cloud) does not significantly affect GNSS signals, so there is little difference in Fix ease between sunny and rainy days. However, heavy rain collecting on the antenna may slightly reduce reception sensitivity. Time of day can influence satellite geometry and ionospheric conditions. The number and distribution of visible satellites change over time; for example, there may be periods (depending on the constellation) when fewer satellites are visible. Daytime ionospheric disturbances caused by solar activity can increase errors, especially for long-distance RTK, making Fix less stable. Therefore, selecting times with favorable satellite geometry or when the ionosphere is more stable improves success rates; early morning or night often offers more stable conditions for maintaining Fix.

Q5. If it still absolutely won’t Fix, what should I do? A. First, implement the countermeasures described above (review environment, check settings, improve communications). If that doesn’t help, consider additional steps. One is rebooting equipment: reset both base and rover and reconnect, which may refresh data and allow convergence to Fix. Another is trying a different base station service—switch to a regional public base network or a VRS service to determine if the issue is specific to a particular base. If the problem persists, consider upgrading equipment; older single-frequency receivers struggle with even slightly degraded conditions, whereas modern multi-GNSS, dual-frequency receivers dramatically improve Fix rates. Many sites that were previously impossible to Fix with older gear become stable with higher-performance units. If Fix continues to be unattainable, it is better to investigate and resolve the cause or upgrade equipment than to proceed with a Float solution. If needed, contact specialized support, provide detailed information on the situation, and request advice.