Five Reasons RTK Won’t Fix: Thorough Explanation of Satellite Reception, Correction Data, Coordinate Setup Errors, and More

RTK (Real-Time Kinematic) surveying is a groundbreaking technique that enables centimeter-level (half-inch accuracy) high-precision positioning in real time using satellite positioning. However, in the field you will often hear complaints that “RTK won’t FIX (a fixed solution can’t be obtained).” If the solution remains a float, positional errors can reach tens of centimeters (tens of inches), potentially causing rework or re-measurement due to insufficient accuracy.

This article takes up five representative causes that are commonly considered as the main reasons RTK won’t fix, and explains each in detail. We cover frequent causes such as poor satellite reception environment, troubles receiving correction data, and errors in reference point coordinates, and present key points to prevent accuracy degradation and work interruptions. Survey professionals should find this useful. At the end of the article we also introduce a new simple surveying solution “LRTK” that can solve these problems.

Contents

• Poor satellite reception environment

• Unable to receive correction information

• Reference point / coordinate setting errors

• GNSS equipment misconfiguration or malfunction

• Baseline distance and atmospheric error effects

• Recommendation: simple surveying with LRTK

• FAQ

1. Poor satellite reception environment

For RTK positioning, it is essential to be able to stably receive signals from multiple GNSS satellites, including GPS and GLONASS, as a prerequisite for obtaining a FIX solution. However, if the satellite reception environment at the site is poor, the number of observed satellites may be insufficient or the data quality required for positioning may not be secured, and a fixed solution may never be obtained. For example, in urban areas surrounded by high-rise buildings or inside forests, the sky view is often blocked and the number of usable satellites tends to decrease. Multipath, where signals reflect off concrete walls, metal surfaces, or water, is also a serious problem. If reflected waves cause distance measurement errors, the RTK ambiguity (integer solution) analysis is disturbed and a FIX becomes difficult to achieve.

Moreover, if powerful radio-emitting equipment such as high-voltage lines or radar is nearby, noise or interference may be added to GNSS signals and reception strength may decrease. Bad weather should not be ignored either. During heavy rain or thunderstorms, ionospheric effects and signal attenuation can increase and RTK may become unstable. Under such poor satellite reception conditions, the risk that the RTK solution remains float and never fixes is high.

Countermeasure: When performing positioning, choose a location with as wide and open a sky as possible. Install the base station antenna at a site with clear line-of-sight and nothing obstructing 360°, and if possible remove obstacles near the survey point for the rover. Also avoid observations near large reflective objects when feasible. If this is difficult, fitting a ground plane to the antenna or using a high-performance choke-ring antenna to reduce multipath is effective. Recently, many GNSS receivers support multi-GNSS tracking and dual-frequency reception; using these increases the number of usable satellites even in poor visibility and helps cancel ionospheric errors, improving FIX rate. If RTK is unstable due to environmental factors, consider changing the time of measurement (measure when satellite geometry is favorable) or supplementing with other methods such as total stations rather than forcing RTK.

2. Unable to receive correction information

In RTK, centimeter-level accuracy is obtained only by continuously receiving real-time correction data sent from a base station (reference point). Therefore, if communication between the base station and rover is interrupted and correction information does not arrive, no matter how long you wait you cannot obtain a FIX solution. When corrections stop, RTK reverts to standalone positioning or DGPS-level accuracy and the solution remains float.

Causes for inability to receive correction information include communication environment and device configuration issues. In radio-based RTK, correction data is lost if the transmission frequency or channel settings of the base and rover radios do not match, or if the line-of-sight is lost and the signal cannot reach. With low-power or simple radio setups, usable communication distance is often limited to a few kilometers, so if the site is extensive you can move out of range. Environments with radio shielding, such as tunnels or building shadows, also cause communication drops. On the other hand, for network RTK that uses mobile Internet such as NTRIP, data may not be received if the site is out of coverage or mobile data is unstable, or if the base station service suffers an outage.

Countermeasure: First, check communication settings for the base station and rover in advance. When using radio, verify that transmission frequency and group ID match on both ends and inspect antenna connections for looseness or breakage. Install the base station antenna as high as possible to secure line-of-sight and extend the communication area by adding relay antennas if needed. When using mobile networks, prepare SIM cards from multiple carriers on-site so you can use the one with the best signal, and consider external antennas or mobile Wi‑Fi routers to boost reception. Also, battery depletion during long surveys is a frequent cause of correction stoppage. Confirm sufficient battery levels for both base and rover beforehand and carry spare power. If you cannot obtain real-time corrections, consider recording raw data via static surveying and doing PPK (post-processing) later instead of insisting on RTK.

3. Reference point / coordinate setting errors

In RTK surveying, it is a prerequisite that the coordinates of the reference point used and the geodetic/coordinate system settings are accurate. If these are wrong, even when RTK has FIXed the resulting coordinates will be offset, causing major errors. For example, entering a known point coordinate with one digit wrong at the base station or selecting the wrong zone number in Japan’s plane rectangular coordinate system can lead to positional deviations of tens of meters. There are real cases where someone entered a coordinate with one digit off and later found the data didn’t match, causing panic—coordinate setting errors are no laughing matter.

Be especially careful on sites using geodetic or coordinate systems different from Japan’s. If the site uses the old Tokyo datum instead of the modern global geodetic system (JGD2011/2022), or uses a local coordinate system, results will not match local references unless proper coordinate transformations are performed. In the vertical direction, forgetting to apply geoid height correction can cause obtained heights to deviate substantially from the site elevations.

Countermeasure: Before surveying, always confirm the coordinates of the reference points to be used and the designated geodetic/coordinate system. Check contract documents and known-point lists and set the correct reference coordinate system in your equipment (for example: JGD2011, specific prefecture zone, etc.). When installing the base station, double-check that the entered known-point coordinates are correct. If possible, observe one known point before starting work to verify that the equipment yields the expected coordinates. When using a local custom coordinate system, perform site calibration using multiple known points to align the instrument coordinates with the local survey coordinates. If you discover a setting mistake afterward, you may be able to salvage recorded raw data by converting it to the correct coordinate system later, but conversion is laborious, so preventing mistakes from the start is best.

4. GNSS equipment misconfiguration or malfunction

System and equipment misconfiguration or malfunction can also prevent RTK from fixing. A basic example is incorrect mode settings between the base and rover. If a receiver that should operate as a base is left in rover mode, or a rover is mistakenly set to fixed/base mode, corrections will not be generated or applied properly and positioning will fail. When using RTK network services, choosing the wrong mount point (virtual reference point for correction data) can result in an incompatible data format and no solution.

Device-specific issues such as problems with the GNSS antenna or cables must not be overlooked. If an antenna connector is loose or a cable is broken, you may not be able to receive satellite signals or correction data properly and RTK will not fix. Field controllers (data collectors) also require careful software settings. As noted above, incorrect geodetic or projection coordinate settings will cause result offsets, and erroneous RTK solution mode settings will prevent correct solutions. Firmware or app bugs/freezes occasionally occur as well. For receivers controlled by tablets or smartphones, there have been cases where an app force-quit stopped correction reception.

Countermeasure: Prevent equipment troubles by performing pre-site checks. Inspect connections of the GNSS receiver, antenna, and radio; confirm power and battery levels. When using equipment at a new site, simulate software settings (geodetic system, coordinate system, antenna height input, communication settings, etc.) from scratch to ensure proper setup. Keep receiver firmware and control apps updated to the latest stable versions and monitor for release notes on bug fixes. During work, if equipment behaves oddly, pause measurement, reboot, or verify with another known point to isolate the cause early. Also attend to basic human error prevention: check bubble levels on the survey pole for plumbness and avoid antenna height input mistakes.

5. Baseline distance and atmospheric error effects

When RTK does not fix, constraints intrinsic to the RTK method such as baseline distance between the base and rover and atmospheric errors must be considered. Generally, the farther the distance to the base station, the greater the differential ionospheric and tropospheric errors between the two stations, and the larger the residuals that cannot be canceled by corrections, making it harder to obtain a fixed solution. Even high-precision RTK receivers specify performance like “horizontal accuracy 8 mm + 1 ppm,” meaning error increases by roughly 1 mm per kilometer of distance. Therefore, if the rover is tens of kilometers from the base, the observation precision needed to resolve integer ambiguities cannot be maintained and the solution becomes unstable. In particular, single-frequency (L1-only) receivers cannot sufficiently correct ionospheric error, so long baselines often take a very long time to move from float to FIX or may never fix.

Solar flares and other ionospheric disturbances, or times when satellite geometry is poor, also reduce FIX rates. Even with no obstructions, if the satellite distribution overhead is biased and PDOP is high, RTK initialization may take longer. Conversely, with multi-GNSS providing 10 or more satellites, RTK can often fix stably even with some atmospheric error.

Countermeasure: Keep the distance between the base station and the survey point as short as possible. If you can deploy your own base, put it near the site; if that’s difficult, use GNSS CORS (continuously operating reference stations) or VRS (virtual reference station) services to effectively shorten the baseline. Before surveying, check satellite availability and avoid times with few satellites or poor geometry—services like the Geospatial Information Authority’s GNSS satellite visibility prediction can show PDOP forecasts. On days with large ionospheric disturbance, avoid high-precision real-time positioning and instead record short observation sessions for later precise processing (PPK or PPP). Don’t be fixated on RTK’s real-time aspect; flexibly switching to other surveying methods as conditions require is the best path toward “zero rework.”

Recommendation: Simple surveying with LRTK

So far we’ve reviewed typical causes and countermeasures when RTK doesn’t easily FIX. Successful high-precision RTK surveying requires attention to many points—checking the surrounding environment, device configuration, and so on—and demands specialized knowledge and experience. This is where the new solution “LRTK” stands out, as it addresses these issues and makes centimeter-level positioning easy for anyone.

LRTK is a new surveying system designed to enable convenient high-precision positioning using smartphones or dedicated small devices. By combining multiple satellite positioning technologies and cloud services, it eliminates much of the complexity associated with conventional RTK operations. For example, without consciously performing advanced tasks such as base station installation, communication maintenance, or coordinate adjustments, LRTK can automatically achieve millimeter-level positioning simply by setting up the terminal at the site. In practice, LRTK also utilizes augmentation signals from the QZSS (Michibiki) satellites, enabling stable positioning even in mountainous areas where cellular service may not reach.

Some benefits of LRTK include:

• Ease of use: Intuitive smartphone-app-centered operation that can be used without special GNSS expertise. No complicated settings or onsite adjustments are required, so users can be up to speed after short training.

• High accuracy: By combining observations from multiple points and advanced cloud correction techniques, LRTK achieves horizontal and vertical positioning accuracy of approximately 1–2 cm (0.4–0.8 in). Using a dedicated monopod allows one-person stable positioning, and averaging dozens of observations can approach sub-millimeter (sub-0.04 in) precision.

• Reliability: Risks such as communication dropouts or configuration errors common in traditional RTK are greatly reduced. Data are automatically saved to the cloud in real time, so positioning logs remain even in the event of device failure.

• Efficiency: Equipment can be carried in a pouch to the site and positioning started with one touch, improving surveying productivity. Reduced post-processing allows you to obtain deliverables on site and proceed to the next task.

Adopting LRTK—leveraging modern technology—can free you from worries about RTK not fixing or failing to achieve accuracy. If interested, check LRTK’s detailed information. Free service brochures are currently available, so please consider requesting materials.

FAQ

Q: If RTK remains in a float solution and won’t fix, what should I do? A: First, check the five causes introduced here—satellite reception environment, correction information, coordinate settings, equipment configuration, and baseline length—one by one to see which might be at fault. Inspect whether you can move to a more open location, whether the base station’s radio reaches you, and whether there are any setting errors. If FIX still cannot be obtained, pausing measurement and waiting for satellite geometry to improve is another option. If real-time FIX is impossible, don’t insist on continuing; consider recording static observations and solving by PPK later.

Q: How many satellites are minimally required for RTK to fix? A: Generally, it is desirable to observe at least five satellites simultaneously for an RTK fixed solution (four for pseudorange differencing plus one for error mitigation). However, if satellite geometry is poor or data quality is low due to multipath, even five visible satellites may not be sufficient. In practice, always having seven to eight or more satellites available is ideal. Multi-GNSS receivers that use GPS, GLONASS, QZSS, Galileo, etc., can more readily secure around ten satellites even in urban areas, improving FIX rates.

Q: Does using a multi-GNSS, dual-frequency receiver increase FIX rate? A: Yes, it does. Multi-GNSS receivers significantly increase the number of available satellites, making it easier to secure the satellites needed for positioning even with limited sky view. Dual-frequency receivers (L1/L2, etc.) greatly improve ionospheric delay correction accuracy and can resolve ambiguities faster than single-frequency units. As a result, time to initial FIX and hold time (the ability to maintain a FIX once acquired) are significantly improved. For stable, high-precision results, use multi-GNSS and multi-frequency receivers where possible.

Q: What is LRTK? A: LRTK is a new high-precision positioning service that serves as an alternative to traditional RTK operations. Combining a smartphone with a dedicated receiver and a cloud-based correction platform, it enables anyone to perform centimeter-level positioning without specialized procedures. Complicated base station setup and coordinate transformations are unnecessary—take the device to the site, push a button, and the survey is complete. Communication and configuration troubles are minimized, and positioning data are automatically stored in the cloud for secure, reliable results. For details, refer to LRTK’s official information.