Why Won’t RTK Fix? 8 Checkpoints for Beginners

RTK (Real-Time Kinematic) is a positioning technique that uses GNSS (Global Navigation Satellite Systems) to obtain high-precision positions in real time. By correcting errors through relative positioning between a base station (reference) and a rover (mobile station), errors that would be several meters in standalone positioning can be reduced to centimeter-level. If an integer-ambiguity-resolved fixed solution (Fix) is obtained, positional accuracy can be within a few centimeters or less, a level reliable enough for surveying and construction sites. On the other hand, if ambiguities remain unresolved and the solution stays as a float (Float), accuracy is limited to several tens of centimeters to about 1 m (3.3 ft), and the position tends to drift over time, remaining unstable. To achieve high-precision results, obtaining a solid RTK Fix is indispensable.

However, beginners attempting RTK positioning often encounter problems like “it never switches from Float to Fix” or “it doesn’t achieve the expected accuracy.” RTK is a very delicate technology; small differences in satellite reception environment or equipment settings can greatly affect results. So when you can’t get a Fix, what should you suspect and check? This article narrows down eight checkpoints beginners should verify when RTK won’t Fix, explaining the causes and remedies for each in an easy-to-understand way. Use this as a guide to diagnose and address “won’t Fix” issues encountered in the field.

Contents

• Insufficient satellite count/geometry

• Effects of nearby obstructions and multipath

• Strong radio interference or noise

• Base-to-rover distance (baseline) too long

• Correction data not being received

• Mistakes in reference point coordinate settings

• GNSS equipment misconfiguration or malfunction

• Issues in measurement procedures

• Achieve high-precision positioning easily with LRTK

Insufficient satellite count/geometry

In RTK, being able to stably receive signals from multiple satellites is a prerequisite for obtaining a Fix. If the number of available satellites is extremely low or satellites are clustered in one part of the sky, the geometric dilution of precision (DOP) worsens and a fixed solution may never be achieved. When observational information from satellites is insufficient, the RTK engine cannot correctly resolve integer biases and remains in a Float state. For practical centimeter-level 3D positioning, it is generally desirable to track at least five satellites simultaneously, and ideally seven to eight or more satellites should be visible.

As a countermeasure, choose an environment and time when as many satellites as possible are visible. Use tools that can simulate GNSS satellite geometry in advance to check observation conditions, and measure during times when satellite count is sufficient and DOP values are favorable. If possible, use a receiver that supports multiple satellite systems such as GLONASS, Galileo, and Japan’s Michibiki (Quasi-Zenith Satellite System) in addition to GPS to increase the number of visible satellites and improve stability. Also check that the elevation mask (which excludes low-elevation satellites) in the receiver or app settings is not set too high—about 15° is a balanced value. Securing a sufficient number of satellites greatly increases the probability of transitioning to a Fix.

Effects of nearby obstructions and multipath

When the sky view is obstructed, RTK reception degrades. Being surrounded by buildings or trees not only reduces the number of available satellites but also weakens signal strength and increases noise, lowering solution quality and making Fix acquisition difficult. Multipath—satellite signals reflected off concrete walls, the ground, or water surfaces—is also a major enemy of RTK. The inclusion of reflected waves introduces ranging errors and disrupts integer ambiguity resolution. In poor reception environments such as urban canyons or dense forests, it is common that the solution remains Float indefinitely.

As a remedy, choose open locations with clear sky views whenever possible. Simply moving away from obstructions such as buildings, trees, or large machinery can increase the number of receivable satellites and make Fixing easier. In some locations like a valley between tall buildings, moving a few meters can noticeably improve conditions. Measures such as placing a metal ground plane under the antenna to suppress ground reflections or mounting the antenna as high as possible on a pole to reduce surrounding reflections can also be effective. The basic principle is to secure satellite visibility. If the environment prevents Fixing, it is wise to stop and change location or time rather than forcing the measurement.

Strong radio interference or noise

Strong radio interference or noise affecting GNSS signals can also prevent RTK from obtaining a Fix. Environments with strong radio sources—directly under high-voltage power lines or near radar installations and radio stations—can superimpose noise on the weak satellite signals and significantly degrade the received S/N ratio. As a result, positioning accuracy can worsen drastically and remain in a Float state. In practice, even nearby construction radios or Wi-Fi routers can introduce noise into GNSS antennas. Additionally, during severe weather such as heavy rain or thunderstorms, ionospheric instability or increased signal attenuation can temporarily destabilize RTK.

To mitigate this, inspect the surrounding radio environment and keep distance from any obvious interference sources. During measurement, stay away from high-voltage lines, keep wireless devices away from the GNSS antenna, and turn off unnecessary electronics to reduce the risk of noise intrusion. If weather is causing instability, prioritize safety and wait for the rain to stop or perform the survey on a calmer day.

Base-to-rover distance (baseline) too long

In RTK, as the distance between the reference base and the rover (baseline) increases, differential error components between the two stations (such as ionospheric and tropospheric delays) grow larger, leaving residuals that cannot be fully canceled by correction data. Consequently, observation accuracy decreases and obtaining a fixed solution becomes more difficult. This is especially pronounced when using single-frequency (L1 only) GNSS receivers, which cannot adequately compensate ionospheric errors, making it take much longer to go from Float to Fix—or in the worst case, never fix. Even high-precision receivers have distance-dependent error specifications like “horizontal accuracy 8 mm (0.31 in) + 1 ppm,” so when the base station is tens of kilometers away, the initial observations required for initialization may not meet necessary precision, and the solution tends to be unstable.

As a rule, keep the base-to-rover distance as short as possible. If you can set up your own base station, place it as close to the survey area as practical. When using a network RTK service, check whether the currently connected base station is too far away. If needed, switch to a closer base station mount point or use a Virtual Reference Station (VRS) correction service to effectively shorten the baseline. Shortening the baseline reduces differential errors like ionospheric effects and greatly improves the time to Fix and overall stability.

Correction data not being received

To achieve high precision with RTK, it is essential to continuously receive real-time correction data from the base station. Therefore, if correction information is not arriving, no matter how long you wait you will not get a Fix. If communication is lost, RTK reverts to standalone positioning and the solution remains Float. For radio-based RTK, problems can include the base and rover radios not being properly linked, or mismatched frequency or channel settings preventing data delivery. Low-power radios or simple portable radios often have limited communication ranges of a few kilometers, so in wide-area sites the signal may not reach. For internet-based network RTK such as NTRIP, the field may be out of coverage with an unstable mobile connection, or the base station service may be experiencing system outages preventing data distribution. If correction data is not being received at all, Float will not progress to Fix.

As a countermeasure, first check the communication status with the base station. For radio connections, verify that transmitter and receiver radio settings (frequency, group ID) match and inspect antenna connections for looseness or breaks. Ensure the rover is within communication range of the base station. For network RTK, confirm that the device has mobile data connectivity and that the NTRIP connection settings (IP, port, mount point) are correct. If your positioning app shows “Age of Diff” or the number of received messages, monitor whether those values are appropriate. Typically, an Age of Diff within a few seconds indicates real-time correction is functioning, but 30 seconds or more means communication trouble. Retry the connection or restart the mobile router to secure stable correction reception—this is a quick route to achieving Fix. Also verify you are selecting correction data formats appropriate for your receiver model (for example, use single-frequency-compatible data for single-frequency receivers, not multi-frequency correction streams).

Mistakes in reference point coordinate settings

In RTK, it is fundamental that the coordinates of the reference point used and the geodetic/coordinate system settings are correct. If these are incorrect, even if RTK is Fixing, the computed coordinates will be offset, resulting in significant errors. For example, entering a known base point coordinate with a digit error, or selecting the wrong zone number in Japan’s Plane Rectangular Coordinate System, can shift results by tens of meters. Confusing different geodetic datums (such as the old Tokyo Datum versus the World Geodetic System) or using a local custom coordinate system also requires care. If correction information is applied without accounting for differences in coordinate systems, the rover’s output coordinates will not match local references unless proper transformations are performed. In the vertical direction, neglecting to apply geoid height corrections will result in heights that differ significantly from the site’s elevation.

As a remedy, carefully verify the reference point coordinates and geodetic/coordinate system settings before starting surveying. Refer to contract documents or reference point sheets and set the correct reference coordinate system in the GNSS receiver or software (for example: WGS xx system, block yy). When setting up a base station, double-check the entered known-point coordinates. If possible, observe a known point before work begins to validate that expected coordinates are obtained. When using a local custom coordinate system, perform a “site calibration” with multiple known points to align the instrument’s coordinate system to local coordinates so that results are consistent. If you discover a setting mistake later, you may be able to salvage data by converting the raw recorded data to the correct coordinate system afterwards, but this requires effort, so preventing setting errors from the start is best.

GNSS equipment misconfiguration or malfunction

Receiver and system configuration errors or equipment faults can also cause RTK not to Fix. A typical mistake is swapping base and rover mode settings. If a device that should operate as a base is left in rover mode—or vice versa—corrections will not be sent or applied properly and positioning will fail. When using a network RTK service, choosing the wrong mount point and receiving data in an incompatible format for your receiver can also prevent a solution. Furthermore, incorrect geodetic or projected coordinate settings in the field controller software will cause the results to be displaced as described earlier, and incorrect RTK solution mode settings (e.g., setting a rover as a base) will prevent obtaining the correct solution.

Equipment-specific issues like GNSS antenna or cable faults must not be overlooked. Loose antenna connectors or broken cables will prevent normal reception of satellite signals or correction data, and RTK will not Fix. When controlling the receiver with a tablet or smartphone, app crashes or freezes can also stop correction reception.

As a countermeasure, thoroughly inspect equipment state and settings before going into the field. Check connections of the GNSS receiver, antenna, and radio equipment, and confirm power and battery levels are sufficient. When using a new site, preconfigure surveying software settings (geodetic/coordinate system, antenna height, communication settings, etc.) and simulate operations to ensure proper setup. Update receiver firmware and control apps to the latest stable versions provided by the manufacturer, and review known-issue advisories. If you notice abnormal device behavior during work, stop measuring early and reboot the system or validate with another known point to isolate the cause. Basic practices such as keeping the survey pole vertical using the bubble level and avoiding antenna height input errors are important to prevent human error.

Issues in measurement procedures

Operational procedures for RTK surveying also require attention. If you start moving immediately after beginning positioning while still in a Float state, the solution may remain unstable and never transition to Fix. Although the RTK engine updates solutions in real time while the rover is moving, during the initial phase data may be insufficient and the solution will follow as Float. Also, if you continue measuring without noticing that a Fix has reverted to Float, you risk recording a large amount of un-fixed data.

As a remedy, when starting RTK measurement, keep the rover stationary for sufficient time until a Fix is obtained before proceeding to full-scale point measurement. Especially when initializing RTK for the first time or during poor satellite geometry, patience of tens of seconds to several minutes may be necessary to obtain a Fix. Even after obtaining a Fix, continuously monitor that “Fix” is maintained in the receiver or app status. If the solution drops to Float, stop immediately, remove environmental causes if possible, re-acquire base station information, and wait to return to Fix before resuming measurement. If you cannot get a real-time Fix despite effort, consider switching to static positioning to record data and perform PPK (post-processing kinematic) later.

Achieve high-precision positioning easily with LRTK

So far we have reviewed typical reasons RTK may not Fix and their countermeasures. Successful high-precision RTK surveying requires attention to many points such as satellite reception and equipment settings, and requires specialized knowledge and experience. One solution that addresses these challenges at once and enables beginners to achieve centimeter-level positioning easily is LRTK.

LRTK (El-Arr-Tee-Kay) is a new positioning system composed of a small RTK-GNSS receiver device that attaches to a smartphone and a cloud service. By combining multiple satellite positioning technologies and internet correction services, it eliminates the cumbersome procedures traditionally associated with RTK operation. For example, at the site you simply connect a dedicated unit to your smartphone and tap a few buttons; the system automatically establishes communication with reference stations and adjusts coordinate systems, allowing millimeter-level positions to be obtained instantly. It supports Michibiki’s centimeter-class augmentation signal (CLAS), maintaining stable positioning accuracy even in mountainous areas without mobile coverage.

Using LRTK brings many benefits. Operation is simple: an intuitive smartphone app UI allows use without specialized GNSS knowledge. Complex setup and field tuning are unnecessary, and a short training session is sufficient to start using it. Yet positioning accuracy remains very high—leveraging multiple base station data and advanced correction algorithms, it achieves approximately 1〜2 cm (0.4-0.8 in) accuracy horizontally and vertically. With a dedicated monopod stand, stable observations can be made by one person, and averaging data over tens of seconds can approach sub-millimeter precision. Reliability is also improved, greatly reducing the risk of communication outages or configuration errors common in traditional RTK. Positioning data is automatically saved to the cloud in real time, so logs are not lost even if a field device fails. Mobility and efficiency are outstanding: pocket-sized devices enable one-touch measurement start on site, dramatically increasing surveying productivity. Because no post-processing is required, you can obtain results on the spot and move on to the next task immediately.

By adopting LRTK, you can be freed from RTK-related issues like “won’t Fix” or “insufficient accuracy.” If you are interested, please check LRTK’s detailed information. Service brochures are currently available for free distribution—feel free to inquire.