Table of Contents

• What Fix, Float, and noRTK mean in RTK positioning

• Cause 1: Poor satellite signal reception environment

• Cause 2: Base station installation or reference coordinate errors

• Cause 3: Base station too far away

• Cause 4: GNSS configuration mismatch (satellites or frequencies used)

• Cause 5: Correction data not received / communication trouble

• What simplified surveying with LRTK means

• FAQ

In high-precision positioning using the RTK (Real Time Kinematic) method, the ideal is to obtain a "Fix solution" and achieve centimeter-level accuracy. However, in the field it is common to encounter situations where Fix is never achieved and the solution remains a "Float," or where corrections do not take effect and the system stays in a "no RTK (single) state." For field workers and managers considering the introduction of surveying equipment on construction sites, understanding why RTK does not fix and taking countermeasures is important. This article explains the five main causes why RTK does not reach Fix and their countermeasures. First, we will confirm the differences among Fix, Float, and noRTK states, and then review remedies by cause. At the end of the article we also introduce simplified surveying using LRTK as a way to resolve such problems and perform surveying more easily.

What Fix, Float, and noRTK mean in RTK positioning

First, let’s grasp the meanings of the status indicators in RTK positioning: “Fix”, “Float”, and “Single (no RTK)”.

• Fix (fixed solution): The RTK solution has converged to integer solutions. Phase differences between satellites that cause error have been reconciled, and high-precision corrections are being applied. Typically centimeter-level positioning accuracy (around ±2 cm) is achieved, making this state suitable for surveying and precision construction. In RTK operation, obtaining a Fix solution is the goal.

• Float (floating solution): Corrections are being received, but the solution has not yet reached integer resolution. It is essentially an intermediate computation result, also called a floating-point solution. Accuracy is below a meter, generally around ±0.5–1 m, and it is less reliable than a fixed solution. In practical applications that can tolerate some error—such as agriculture or navigation—Float solutions may be usable, but they are insufficient for precise surveying.

• Single (single solution / no RTK): No corrections from a base station are being applied; this is standalone positioning. This is normally the position computed by the GNSS receiver alone, with errors of several meters (±a few meters to about 10 m). It may be displayed as “no RTK” or “DGPS off.” Since RTK benefits are not realized, this state cannot be used for tasks requiring high accuracy.

Accuracy expectations differ greatly by status: Fix yields centimeter-level, Float at best decimeter-level, and Single meter-level. Therefore, where high precision is required, you must transition from Float or Single to Fix as quickly as possible. Normally, if the sky is open and enough satellites are visible, it is common to enter Fix within tens of seconds to a few minutes after starting RTK. With high-performance receivers and algorithms, Fix can sometimes be reached in about 20 seconds once conditions are met. If Fix is not obtained after more than 5 minutes, some factor is likely preventing convergence of the solution. Check whether you recognize any of the causes introduced below and try appropriate countermeasures to see if the situation improves.

Cause 1: Poor satellite signal reception environment

In environments surrounded by buildings or trees, obtaining an RTK Fix becomes extremely difficult. Radio waves from GNSS satellites travel in straight lines and are easily blocked by obstacles, so in locations with poor sky visibility the number of receivable satellites decreases and signal strength weakens. Also, if the receiver picks up signals reflected off metal surfaces or concrete walls, multipath errors occur and destabilize the positioning solution. Under such poor reception conditions, even if correction information arrives, the necessary observation data may be insufficient, and the engine cannot converge integer ambiguities (error parameters). As a result, the system may remain Float indefinitely and never reach Fix, or in the worst case corrections may not be applied and the solution stays Single.

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

• Move to a location with open sky: If the measurement site is inside a garage, next to a stand of trees, or in a building shadow, first move to a wide, open place with visible sky and re-run positioning. Locations with unobstructed sky in all directions can capture many satellites, greatly shortening the time to Fix.

• Install the antenna properly: Place the GNSS antenna as high as possible and away from surrounding obstructions. Raising the antenna onto a roof or above obstacles with a tripod or pole can improve reception. Avoid placing the antenna directly on the ground or a car hood; use a stable dedicated pole or magnetic mount. If there are strong reflectors nearby (large vehicle bodies, metal fences, etc.), arrange the setup to keep the antenna as far from them as possible.

• Obtain Fix first, then move to the desired measurement point: If you must measure a point surrounded by obstacles, rather than trying to get Fix right on that spot, start RTK at a nearby open location and achieve Fix there, then slowly move to the measurement point. Some receivers can maintain Fix for a short period even when moving into worse visibility after Fix has been achieved. Even if it falls to Float during movement, the chance of returning to Fix increases if satellites are reacquired.

Also pay attention to the impact of radio interference beyond sky visibility. Strong local radio waves (for example, construction communication devices or high-voltage equipment) can disturb GNSS reception. If you suspect such equipment nearby, measure during times when it is not in use or apply noise mitigation to the antenna.

Cause 2: Base station installation or reference coordinate errors

In RTK, the rover applies corrections based on the base station’s accurate position information. If there is any problem on the base station side, the rover may never obtain a Fix solution. A representative example is a base station coordinate input error. If the base station’s latitude, longitude, or height is set incorrectly, or if a provisional coordinate with a large error was used, the initial RTK computation will be off and resolving integer ambiguities may take longer or fail to converge. Especially if the base station coordinate is off by tens of meters or more, the inconsistency with correction data can significantly delay convergence to a fixed solution.

Also, improper base station antenna installation is problematic. If the base station antenna is placed in an unstable location and moves during observation, or tilts due to strong wind, the base station cannot continue making accurate observations. Naturally, corrections sent to the rover will be unstable, causing Fix to drop or return to Float. Furthermore, if the environment where the base station is installed is poor (narrow sky view, nearby tall buildings, etc.), the quality of the correction data itself is degraded. Even if the rover is in a very open location, you cannot expect a high-precision Fix if the base station data used for corrections cannot be trusted.

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

• Measure the base station coordinates accurately: When installing a new base station, ideally perform a roughly one-hour averaged positioning or calibration using a known point to obtain coordinates as close to the true values as possible. If you used coordinates obtained from a short measurement, they may have large errors; consider re-measurement or comparison with public reference points. When installing on an existing reference point, be mindful of datum differences (for example, whether coordinates are in the World Geodetic System or a Japanese datum). Recheck for input mistakes and correct values as needed.

• Keep the base station antenna from moving: After installation, ensure the antenna position never changes. If it falls or shifts for any reason, RTK must be restarted from scratch. Stabilize the antenna with fixtures or weights and place it where workers will not accidentally touch it. If it is moved, stop RTK immediately and reinitialize the coordinates.

• Maintain good reception environment for the base station: As in Cause 1, satellite reception environment matters for the base station as well. Install the base station with as much open sky as possible and choose an environment with minimal reflection and blockage. If the base station observes only a few satellites, the corrections available to the rover will be limited. Also inspect hardware: check for antenna cable breaks or looseness and ensure stable power supply.

If you use public online base station services or third-party base station data, you may also encounter cases where Fix does not occur due to problems on the provider’s side—for example, poor observation conditions or maintenance that degrades accuracy. There is little the user can do in that case besides switching to another service if available or trying again later. If you combine your own base station with external data, also watch out for mismatched coordinate systems (mixing local coordinates with a global datum, etc.).

Cause 3: Base station too far away

When the distance (baseline) between rover and base station is too great, RTK has more difficulty achieving Fix. RTK correction works by canceling common error sources between base and rover, but as the distance between the two points increases, the errors each receives differ and the correction effect diminishes. In particular, ionospheric and tropospheric effects grow with distance, and at long ranges the measurements cannot fully cancel each other out. As a result, integer ambiguities become unstable and convergence to a fixed solution takes a very long time, or the system may remain Float.

In general, RTK is more stable and higher-precision with shorter baselines. A practical guideline is that within about 10 km is desirable. Up to around 10 km, common errors between base and rover are mostly canceled and centimeter-level accuracy is relatively easy to obtain. However, when distance increases to 20 km or 30 km, residual errors that cannot be corrected accumulate and convergence becomes unstable. It is still possible to get Fix with good algorithms and conditions, but maintaining accuracy requires more effort. At distances over 50 km, achieving a fixed solution with ordinary RTK becomes difficult; in such cases consider satellite augmentation or network-type services (discussed later).

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

• Use the nearest possible base station: If you operate your own base station, plan placement so it is not too far from the rover’s work area. For large sites, consider relocating the base station as needed. If using an existing service, choose the nearest base station data or use VRS when available.

• Use multi-frequency receivers for long distances: As baseline increases, ionospheric error influence becomes significant. Receivers capable of observing multiple frequencies (L1, L2, L5, etc.) are advantageous for mitigating such errors. Dual-frequency or higher RTK has a better chance of obtaining Fix at longer distances than single-frequency systems. For long-distance links, use dual-frequency or better equipment at both ends if possible.

• Consider time of day and ionospheric activity: During periods of high solar activity or daytime when the ionosphere is disturbed, long-distance RTK is more difficult. When doing surveys over tens of kilometers, aim for times when ionospheric disturbance is lower (generally nighttime to early morning) to increase success rates. For large-distance measurements, consider methods other than real-time RTK—such as reference network solutions or PPP (post-processed or static positioning).

Cause 4: GNSS configuration mismatch (satellites or frequencies used)

If the satellites or signal settings used by the base and rover do not match, RTK will not Fix. RTK requires both units to compute using observations of the same satellites. If one unit is tracking GLONASS while the other is not, or if frequency band settings differ, common observations cannot be obtained and corrections cannot be applied correctly. For example, if the base station is tracking GPS+GLONASS but the rover is set to GPS only, GLONASS-derived corrections are ignored, reducing the effective number of satellites and making the solution less stable. Conversely, even if the rover supports multi-GNSS, if the base station data contains only GPS, RTK will effectively use GPS only, which in some conditions may result in a Float solution.

Also be aware of correction data format incompatibility when combining older or different vendors’ equipment. RTK corrections use the RTCM standard, but depending on version and message types, the receiving unit may be unable to interpret some information. If the base station outputs additional messages for GLONASS or Galileo that the rover does not support, the rover may not process them correctly and Fix may never be achieved. Additionally, specialized correction services such as Japan’s QZSS (Michibiki) augmentation signals may require specific settings or compatible equipment.

Countermeasures: When introducing an RTK system, unify settings between base and rover.

• Use the same GNSS satellite systems on both units: Enable all available satellite systems (GPS, GLONASS, Galileo, BeiDou, QZSS, etc.) and maximize the number of commonly tracked satellites. Check the settings to ensure no system is disabled on either unit. GLONASS is particularly often turned off, so watch for that. Use multi-GNSS-capable receivers whenever possible to get corrections from multiple satellite systems and improve Fix stability.

• Align frequency band usage: Confirm that L1/L2 (and other bands) usage matches between base and rover. Dual-frequency receivers usually use both automatically, but if one unit is single-frequency, the other must be set to L1-only correction mode (or upgrade both to dual-frequency). Be especially careful about interoperability in mixed environments.

• Verify correction format compatibility: Check the RTCM message types output by the base station or NTRIP service. At a minimum, ensure that `1005` (base station coordinates) and observation messages for each satellite system (GPS: 107x, GLONASS: 108x, etc.) are included. If the rover is an older model and does not support newer RTCM messages, missing data can prevent Fix. In that case, change the base station’s output to compatible message types or update firmware on the receiver.

If reviewing these settings does not solve the issue, try restarting the equipment. Software anomalies can occasionally prevent settings from reflecting correctly. Reboot the entire RTK system and start up in the order base station → rover; this can allow correct settings to be applied and lead to Fix.

Cause 5: Correction data not received / communication trouble

If the correction information from base to rover is not being received, Fix will not 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 typical example is network issues when receiving corrections over the internet via NTRIP. In mountainous areas mobile data may be unstable, or a smartphone tethering setting may disconnect—if corrections do not arrive, the solution will revert to Float or Single. Misconfigurations of the NTRIP host name, mountpoint, or login credentials that prevent establishing a connection are also common. Similarly, when corrections are transmitted via short-range radio or digital radio, stepping out of coverage or experiencing interference can cause missing correction data and the RTK solution to fail to maintain Fix.

Even when communication is established, intermittent loss of correction data makes maintaining Fix difficult. For example, if the base station transmission interval is very long (e.g., only once every 30 seconds), the rover may revert to Float between updates. Or if communication is coming through but the data has many errors (packet loss or CRC errors), the receiver may not be able to reconstruct the information needed for Fix.

Countermeasures: Check whether correction data is being received by inspecting communication status. Many RTK-capable devices and apps display correction reception status, “Differential age,” and “base station latency” as numerical values. If these are not updating or errors are shown, suspect a communication fault.

• Verify internet connection: If using NTRIP, ensure the rover-side device (smartphone, tablet, router) is definitely connected to the internet. If signal strength is poor, move a bit, toggle airplane mode, or try basic connectivity fixes. Because LTE may be unstable outdoors in some areas, consider trying a different SIM or another carrier (dual-SIM routers that auto-switch to the stronger line are convenient).

• Fix NTRIP configuration errors: Check host name (or IP), port number, mountpoint, username and password; a single incorrect item will prevent receiving corrections. Carefully check for errors such as uppercase/lowercase mismatches or extra spaces. Deleting and re-entering the settings can help catch typos.

• For radio communication, ensure line-of-sight and mitigate interference: If using your own radio link, confirm sufficient antenna line-of-sight. Place the base station antenna as high as possible and avoid obstacles between it and the rover. Low-power short-range radios practically limit range to about 1 km, so beyond that consider using repeaters or switching to licensed higher-power radios. If other devices use the same frequency and cause interference, change channels or disable the other noise sources.

If communication temporarily cuts corrections, stay calm and wait a bit. Many GNSS receivers use internal prediction to maintain positioning for several tens of seconds after corrections stop; if communication is restored within that window, the system can return to Fix. If communication frequently drops, apply the above countermeasures to stabilize it, or consider measurement methods that do not require continuous communication (for example, direct satellite augmentation services described later).

What simplified surveying with LRTK means

We have reviewed the main causes and countermeasures for RTK not reaching Fix. Still, in the field you may face situations such as “I cannot move the antenna,” “the distance must be long,” or “I lack expertise and worry about settings.” In such cases, our LRTK simplified surveying solution can be helpful.

LRTK consists of a compact, high-performance RTK-GNSS receiver and a smartphone app, developed to make high-precision field positioning easier and more reliable. With several features that set it apart from conventional equipment, it covers the factors that hinder Fix both in hardware and software.

• Multi-GNSS and multi-frequency support for stable positioning: LRTK receivers support not only GPS but also GLONASS, Galileo, Michibiki (QZSS), and other systems, and can perform positioning on dual frequencies L1/L2. This ensures a sufficient number of satellites even in urban areas and improves ionospheric error removal. It prevents satellite shortage and accuracy degradation over long baselines, making Fix easier to obtain in shorter timeframes.

• Support for CLAS augmentation signals: Some LRTK models can receive CLAS—centimeter-level augmentation provided by Japan’s Michibiki—enabling centimeter-level positioning even where no RTK base station can be installed. This flexibility allows high precision in mountainous or out-of-coverage areas where conventional RTK is difficult. The ability to obtain corrections directly from satellites without worrying about communication outages or baseline length constraints is a major advantage.

• Easy operation via smartphone linkage: Dedicated apps let you intuitively manage base and rover settings and connection status. Satellite reception and correction data status are displayed at a glance, enabling rapid diagnosis if Fix is not achieved. Complex NTRIP settings can be reduced to choosing a pre-registered server, greatly decreasing configuration errors. This usability allows field personnel without specialized knowledge to operate correctly.

• Cloud integration and tilt compensation: Positioning results can be synchronized to the cloud in real time so data sharing and checks are completed before returning to the office. Newer models include a tilt sensor in the receiver that automatically corrects for pole tilt, allowing accurate coordinates even when the pole is not vertical. This prevents missed measurement points in tight spaces and improves work efficiency.

In these ways, LRTK offers a proprietary solution that balances RTK accuracy and usability. It is designed to minimize common “won’t Fix” troubles in the field and enable anyone to perform high-precision surveying easily. If you are struggling to achieve Fix in your current setup, consider switching to simplified surveying with LRTK. It can be a reliable partner for consistently obtaining Fix under complex conditions.

FAQ

Q1. How much difference in accuracy is there between Fix and Float? A. As a general guideline, Fix solutions are typically within ±a few centimeters, while Float solutions have errors of ±tens of centimeters. In a noRTK (single) state, errors of ±several meters or more are possible. For example, in the LRTK system case, the targets are within 10 m for noRTK, within 1 m for Float, and within 2 cm for Fix. Therefore, for tasks requiring precise positioning, Float or Single is insufficient—always obtain Fix before accepting measurement results.

Q2. What is the minimum number of satellites needed to obtain an RTK Fix? A. It depends on the algorithm, but commonly five or more common observations are required. Four GPS satellites alone is barely enough for standalone positioning and not sufficient for an RTK fixed solution. If both base and rover are tracking five, preferably six or more, common satellites, the chance of Fix increases. Modern receivers supporting multi-GNSS can use 10–20 satellites simultaneously, reducing cases where satellite shortage prevents Fix. However, satellite geometry is also important: if satellites are concentrated in one portion of the sky, accuracy may remain poor even with many satellites. Choosing times when satellites are broadly distributed in the sky can accelerate reaching Fix.

Q3. How long does it normally take to reach RTK Fix initially? A. Under good conditions, reaching Fix often takes 30 seconds to 2 minutes. With unobstructed sky and stable satellite signals, receivers can sometimes reach Fix within a minute of startup. Conversely, in poor environments or when initial base data reception is delayed, you may remain in Float for more than 5 minutes. Once Fix is obtained and measurements continue, Fix is basically maintained unless communication is lost or conditions change. If Fix does not occur after 5 minutes, review the causes discussed in this article and consider restarting the receiver or moving location to obtain Fix more quickly.

Q4. Do weather or time of day make Fix harder? A. Weather (rain or cloudy skies) itself does not largely affect GNSS signals, so there is little difference in RTK Fix performance between sunny and rainy days. Heavy rain accumulating on the antenna can slightly reduce sensitivity. Time of day affects satellite geometry and ionospheric conditions. The number of visible satellites changes over time; for example, there may be temporary reductions in visible satellites around 2–4 p.m. (depending on satellite systems used). During daytime, solar influence can increase ionospheric disturbances, especially making long-distance RTK more error-prone and Fix less stable. Therefore, if possible, choose times with favorable satellite geometry or more stable ionospheric conditions—early morning or nighttime tends to be more stable for maintaining Fix.

Q5. If Fix still cannot be obtained, what should I do? A. First, implement the countermeasures for the causes described above (review environment, check settings, improve communications). If that does not help, several additional measures exist. One is restarting equipment: reset both base and rover and reconnect, as refreshed data may allow the solution to reconverge to Fix. Another is trying a different base station service if available—switching to a regional public base station network or a virtual reference station (VRS) service can help determine if the issue is device-specific. If problems persist, consider upgrading equipment. An older single-frequency receiver may fail to Fix in slightly poor conditions, while a modern multi-GNSS, dual-frequency receiver (L1/L2 support) can dramatically increase Fix rates. There are many cases where upgrading to high-performance equipment allowed stable Fix where it was previously impossible. If Fix cannot be achieved long-term, rather than proceeding with a Float solution, investigate the cause or review your equipment to ensure accuracy. If needed, contact specialist support and provide detailed information to get advice.