RTK positioning (Real-Time Kinematic) can provide centimeter-level high-accuracy position information (Fix solution) when conditions are favorable. However, in the field it is not uncommon to encounter problems such as “RTK not achieving a Fix.” There are various causes for not obtaining a Fix solution, but in many cases the issue can be resolved by reviewing basic points. This article explains five checkpoints to verify when RTK does not Fix. Please use this as a reference to help stabilize positioning.

Table of Contents

• Check satellite reception status

• Check positioning environment (obstructions and multipath)

• Check correction data reception and communication status

• Check base station settings and baseline length

• Check GNSS receiver settings and hardware

• Simple surveying with LRTK

• FAQ

Check satellite reception status

The first thing to check is the number and geometry of available satellites. For RTK positioning, it is important to be able to stably receive signals from at least five satellites. If the number of satellites is low or they are clustered in a particular direction, there may be insufficient information for position calculation, making it difficult to obtain a fixed solution (Fix). Generally, three-dimensional positioning is possible with four satellites, but to obtain a Fix solution it is desirable to use 5–6 or more satellites simultaneously. Check the number of GNSS satellites captured and DOP values (Dilution of Precision) on the positioning software or receiver status screen to ensure the required number of satellites is being met.

Satellite geometry balance is also important. If satellites are clustered in one area of the sky, the DOP will be high (poorer accuracy) and the Fix solution will not be stable. The more evenly satellites are distributed across the sky, the lower the DOP and the better the accuracy. If satellite geometry is poor at the current time, consider checking satellite visibility predictions with tools such as a GNSS planner and performing surveying at a time with better geometry. Also check whether the elevation mask in the receiver settings (which excludes low-elevation satellites) is set too high. Setting the elevation mask around 15° allows moderate use of low-elevation satellites, balancing satellite availability and accuracy. Using a multi-GNSS receiver that supports multiple GNSS constellations (GPS, GLONASS, Galileo, Michibiki, etc.) increases the number of usable satellites and helps improve the Fix rate.

Check positioning environment (obstructions and multipath)

The surrounding environment at the site is also a major cause of RTK not achieving a Fix. GNSS signals can be blocked or reflected (multipath) by building facades, tree branches and leaves, and other obstacles. In locations with a narrow sky view above the positioning antenna, it is difficult to secure a sufficient number of satellites and obtain a Fix solution. In addition, nearby tall buildings, metal fences, large vehicles, etc., can produce reflected erroneous signals, causing errors in position calculation.

As a countermeasure, the basic rule is to position yourself in as open an area as possible. If you can move to a location with an unobstructed sky, moving just a few meters may increase the number of received satellites and lead to a Fix. If you must survey near buildings or structures, try raising the antenna as high as possible or slightly shifting the measurement point. Also, initializing in an open-sky location to achieve a Fix before moving to the target point can be effective. Some receivers can maintain a Fix state for a short period even if the environment worsens after the Fix is obtained.

Multipath mitigation is also important. If a ground plane (conductive plate) can be attached to the antenna, do so to block reflections from the ground and underside. High-performance antennas and receivers may include multipath reduction features, but the fundamental approach is to create an environment that avoids reflections. In addition, check whether there are strong radio interference sources nearby (high-voltage lines, communication antennas, etc.). Strong electromagnetic fields can add noise to GNSS signal reception and impede Fix. Reviewing the radio environment at the site is thus a quick route to obtaining a Fix solution.

Check correction data reception and communication status

RTK positioning cannot achieve a Fix unless correction data from the base station is being received. Therefore, confirm that correction data is being correctly received. If using network RTK, first check the NTRIP connection status. On the dedicated app or receiver screen, confirm that a message such as “Correction data: Receiving” is displayed and that the communication icon indicates normal operation (e.g., green). If it shows not connected, recheck the NTRIP settings (connection URL, port, mountpoint name, user ID/password). Even a single character error will prevent connecting to the server. If using a cellular connection, verify that the smartphone or mobile router has internet access and sufficient signal strength.

If correction data is being received but a Fix is not obtained, pay attention to the content of the received correction information. For example, check that the satellite systems used by the base and rover are not mismatched. If one side is using GLONASS while the other has GLONASS turned off, satellite data will not align and a Fix solution will not be achieved. Make sure both units’ settings match. Also check correction data format and frequency band. If you are using a single-frequency receiver, you need corrections suitable for single-frequency (e.g., MSM4 format); for multi-frequency receivers, choose higher-precision multi-frequency corrections (e.g., MSM7 format). Receiving an unsupported format will prevent correct interpretation and block a Fix.

Continue to monitor communication state. If there is a time lag in correction data or frequent packet loss, the solution may drop to Float or become unstable. If the receiver displays items such as “Age of Differential” or the number of RTCM messages received, you can check whether corrections are arriving without delay. If the delay is large, improve the communication environment or disconnect and reconnect. In some cases, trying a different NTRIP service or another communication method (e.g., changing SIM carrier, switching to a Wi‑Fi router) can be effective. For local radio RTK, check the radio reach and channel interference. If obstacles block radio between base and rover, corrections will be cut off, so ensure line-of-sight installation and appropriate antenna heights.

If using a Virtual Reference Station (VRS) service, also confirm that the approximate rover position is being correctly transmitted. If you registered your position incorrectly during initial setup or position transmission is turned off, appropriate correction data will not be provided and Fix will not occur. Recheck the “position transmission” setting in the connection configuration.

Check base station settings and baseline length

Next, check for problems arising from base station settings or its position. If you are deploying your own base station, confirm that the base station coordinate settings are accurate. It is ideal to set base station coordinates to known values with as little error as possible. If you operate with provisional coordinates, setting values that are far from the actual location can introduce offsets in initial solution values and destabilize Fix. In particular, errors of tens of meters or more can cause integer ambiguity initialization to take longer or fail. If operating in a common public coordinate system, ensure the base station’s geodetic datum (JGD2011, WGS84, etc.) matches the rover’s. If the coordinate systems differ between base and rover, offsets will appear after applying corrections and the Fix may fail.

The baseline length (distance between base and rover) is also a point to verify. RTK accuracy and time to Fix tend to degrade as baseline length increases. Generally, baseline lengths within about 10 km make obtaining a Fix easier, but as distances increase to 20 km or 30 km, ionospheric and tropospheric differential errors grow, making Fix slower or less stable. At distances over 50 km, Fix may rarely be achieved depending on conditions. As a countermeasure, if possible place the base station closer to the work area, or use public Continuously Operating Reference Stations (CORS) or VRS services to effectively shorten the baseline. Network RTK services typically generate virtual base stations near the user, enabling maintained accuracy even at long distances. Conversely, if your local RTK base is too far, consider using a service or increasing the number of base stations.

Also note that the base station’s installation environment affects quality. If the base antenna is surrounded by high-rise buildings or placed in a multipath-prone environment, that error will propagate to the rover. Install base stations in sites with good visibility, measure antenna height accurately, and ensure the base is functioning correctly (not stopped, power and connection normal).

Check GNSS receiver settings and hardware

Finally, check the settings and hardware of the GNSS receiver and peripheral equipment in use. Surprisingly, equipment connection failures or misconfigurations can cause Fix failure. For example, if using an external antenna, inspect for loose or broken cables. If the antenna connector is not firmly connected, satellite signals will weaken and sufficient positioning accuracy cannot be obtained. If equipment that previously worked suddenly no longer Fixes, suspect antenna cable problems or receiver hardware failure. For RTK devices that pair with smartphones or tablets, app issues or freezes may be the cause. In that case, restart the app or the phone and reconnect.

Also review the receiver internal settings. Confirm that positioning mode and satellite settings have not changed inadvertently. For example, if the rover is left in “Static” mode while moving, the solution may not stabilize; conversely, measuring a static point for a long time in “Kinematic” mode can introduce unnecessary errors. Pay attention to ON/OFF settings for the satellite constellations being received. As noted earlier, base and rover must use the same GNSS systems; if one has GLONASS disabled, either disable GLONASS on the other or enable it on both. Some positioning software will reach a Fix after reloading base station information, so try re-acquiring base data.

On the hardware side, do not overlook antenna installation practices suitable for the environment. Mount the antenna as level as possible and avoid tilt. Tilt can cause biased satellite reception patterns and degrade accuracy. When using a pole or tripod, check level with a spirit level. Raising the antenna height reduces the influence of surrounding obstacles, but secure it against wind-induced sway. Also, restarting devices can be effective: power off both base and rover, then power the base up first and start the rover afterward.

If RTK still does not Fix, consider equipment limitations or external factors. Single-frequency receivers in particular may take longer or be unstable in achieving Fix due to ionospheric errors. If possible, using multi-frequency-capable equipment can greatly improve performance. Solar activity and atmospheric conditions can temporarily reduce accuracy; in such cases, wait and retry later.

Also check for GNSS receiver and app firmware/software updates. Older versions may contain bugs affecting RTK solutions; applying the latest firmware from the manufacturer or provider can improve Fix rates. Keeping systems up to date helps achieve stable Fix solutions.

Simple surveying with LRTK

Above we introduced the points to review when RTK does not Fix. Even with these in mind, some users may find device handling difficult or want an easier way to perform surveying. For those users we recommend simple surveying with LRTK. The LRTK series are compact, high-precision GNSS receivers provided by Refixia, aiming to enable anyone in the field to use centimeter-accuracy positioning easily.

LRTK receivers are pocket-sized yet support multi-GNSS and multi-frequency, achieving high-precision RTK positioning in conjunction with a dedicated app. Usage is simple: connect to a smartphone or tablet and operate the app. The app guides complex settings, so no specialized knowledge is required. For example, the smartphone-integrated model LRTK Phone is an ultra-compact receiver that attaches to an iPhone and weighs only 125 g. It can be carried on-site and used for immediate positioning and recording. Some models include tilt compensation so the tip position can be automatically corrected even when the antenna is tilted.

They also support CLAS satellite augmentation signals provided by Japan’s Quasi-Zenith Satellite System “Michibiki,” allowing receipt of corrections via satellite even in mountainous areas without internet access to obtain a Fix solution. Obtained positioning data can be linked in real time with the cloud, enabling on-site sharing of measured coordinates and notes. Introducing LRTK simple surveying lets site personnel handle tasks that previously required surveying specialists, lowering the barrier to RTK positioning and directly improving on-site productivity.

FAQ

Q1: What is the minimum number of satellites required to obtain a Fix in RTK? A: Theoretically, three-dimensional positioning is possible with four satellites, but to obtain a stable Fix solution in RTK it is said that 5–6 or more satellites are required. More satellites are better, and using receivers that can access constellations in addition to GPS—such as GLONASS, Galileo, and Michibiki—increases satellite availability and improves the Fix rate.

Q2: If RTK does not Fix easily, how long should I wait? A: In good environments, a Fix is normally obtained within seconds to a few minutes after powering on the receiver or starting positioning. If a Fix is not achieved after 5 minutes, there is likely some problem. At that point, recheck the points discussed in this article (satellite count, environment, correction data reception, etc.). Continuing to measure in a long-term Float state will not improve accuracy, so identifying the cause and taking corrective action is important.

Q3: Can weather or time of day make Fix more difficult? A: Rain or clouds generally do not significantly attenuate GNSS signals, but ionospheric disturbances and satellite geometry can cause time-of-day effects. For example, it is said that accuracy tends to degrade during daytime hours around 14:00–17:00 due to ionospheric effects. In urban areas satellites can also be at low elevations during specific times and more likely to be obstructed by buildings. If environmental factors make Fix difficult, try shifting the measurement time.

Q4: Is it acceptable to measure using a Float solution? A: A Float solution is less accurate than a Fix, typically with errors of tens of centimeters to about 1 meter. For precise surveying or construction management, a Float solution is inadequate. If a Fix cannot be obtained quickly, do not hastily record Float values; instead wait for a Fix or attempt measurement again later. If a Fix is impossible, switch to Static surveying (long-duration observation with post-processing) or take multiple quick measurements and average them to improve accuracy.

Q5: What measures are available when the base station is far away? A: When the base station is far away, obtaining a Fix becomes more difficult. Using a public network RTK service (VRS) is effective if possible. VRS services generate a virtual base station near the user, solving distance-related issues. If you must cover a long distance, consider installing repeater stations or using higher-power radios to strengthen communications. If still difficult, temporarily relocating the base station closer to the measurement area or using post-processing (PPK) analysis is also an option.