Can RTK Be Used on Rainy Days? 5 Factors That Reduce Accuracy

RTK is a convenient technology that allows centimeter-level positioning to be used on-site (cm level accuracy (half-inch accuracy)), and it is utilized in a wide range of fields such as civil engineering, construction, surveying, agriculture, and infrastructure inspection. On the other hand, what many field personnel are concerned about is whether it can really be used on rainy days. Although it would achieve a stable fix in clear weather, when it rains initialization can take longer, the values may not settle, communications can become unstable, and variations in the vertical direction may become noticeable—many people may have experienced such issues.

To put it simply, RTK can be used on rainy days. However, it may not operate under exactly the same conditions as on a sunny day. Rain itself does not instantly make RTK unusable, but during rainfall multiple adverse conditions tend to coincide, and as a result accuracy degradation and operational troubles are more likely to occur. In other words, the core issue is less the rain itself and more the changes in surrounding conditions that rain causes.

For example, in rainy conditions error factors increase simultaneously: changes in reception caused by antennas and equipment getting wet, degraded visibility and influences from the surrounding environment, instability of communication equipment, pole tilting due to muddy footing, and reduced accuracy of workers' checks. If you carry out work using your usual procedures without understanding these factors, you may unknowingly accumulate errors of several cm (several in) or more.

In this article, we address the question of whether RTK can be used on rainy days, organizing the practical considerations you should keep in mind and explaining five factors that tend to cause accuracy degradation in wet weather. We then detail countermeasures to maintain accuracy on site and perspectives for deciding whether to continue or stop operations. If you want to be able to handle RTK calmly even on rainy days, please read through to the end.

Table of Contents

• Can RTK be used even on rainy days?

• Factor 1 Changes in reception conditions due to raindrops and water films

• Factor 2 Increase in multipath that tends to occur during rainy weather

• Factor 3: Instability of correction information caused by deterioration of the communication environment

• Factor 4 Errors caused by deteriorating underfoot conditions and changes in equipment orientation

• Factor 5: Decline in Work Judgment and Verification Quality

• Practical measures for using RTK on rainy days

• How to tell the difference between rain you can continue working in and rain that should make you consider stopping

• Summary

Can RTK be used even on rainy days?

RTK is a system that combines correction information from a reference station with the satellite signals received by a rover to obtain high-precision positions in real time. Judging only by how it works, rain does not necessarily render it immediately unusable. In practice, it is not uncommon for RTK to be operated in light rain or intermittent rain in the field.

The important point here is that managing conditions becomes more critical for RTK on rainy days than on clear days. RTK inherently only delivers high precision consistently when many conditions are met — satellite reception conditions, stability of correction information, coordinate system settings, consistency with known points, management of antenna height, and the line of sight of the surrounding environment. In rainy conditions some of these factors are more likely to degrade, and even if it appears to be Fix, it may be a poor-quality Fix.

A common misconception on site is the judgment that everything is fine simply because a Fix has been obtained. On rainy days, even when a Fix is displayed, internal observation conditions can deteriorate. In particular, the vertical direction tends to be less stable than the horizontal, and slight changes in attitude or reception conditions are likely to be reflected in the results. Therefore, in rainy conditions it is more important than usual to ensure the quality of the fixed solution, to verify against known points, to re-observe, and to secure sufficient observation time.

Also, it is necessary to distinguish between the effects caused directly by rain itself and environmental factors that are likely to occur simultaneously on rainy days. For example, in practice, reflections from wet ground or wet structures, workers’ rainwear more easily coming into the vicinity of antennas, difficulty operating touch controls on communication devices, and difficulty keeping poles straight can be bigger problems than the mere presence of rain clouds.

In other words, RTK can be used on rainy days, but the practical answer is that to maintain accuracy you need to understand the error factors specific to rainy conditions and change your operational procedures. From the next chapter, we will organize the causes of accuracy degradation into five factors and examine them in detail.

Factor 1 Changes in reception conditions due to raindrops and water films

The first factor is that reception conditions change due to raindrops and water films on equipment surfaces. Because RTK handles weak signals from satellites, even slight changes in the conditions around the antenna can affect observation conditions. In particular, when water remains attached to antenna covers or equipment surfaces, conditions are no longer the same as in clear weather.

Of course, general RTK receivers are designed for outdoor use, so a little rain won't immediately produce large errors. However, as the rain gets heavier, a continuous film of water can more easily form on the antenna surface, causing subtle changes in reception stability. This rarely causes serious errors on its own, but when combined with conditions such as poor satellite geometry, limited sky visibility, or many nearby reflectors, it can become a factor that makes maintaining a Fix unstable.

Particularly important to watch for are conditions where raindrops tend to accumulate on the antenna and where contamination that includes splashed mud adheres. When not only water but mud and dust are mixed in, the surface becomes even more uneven, which can lead to degraded reception. In the field, even if there is no problem in the morning, the antenna surface can gradually become dirty as work continues, and accuracy may become unstable from the afternoon. In such cases, it is not uncommon for the cause to be simply the condition of the antenna surface rather than communications or settings.

Also, on rainy days workers are more likely to use umbrellas, hoods, and rain covers. If these intrude too close to the antenna, they can partially block signals from satellites or alter reflection conditions. In particular, when observing while holding a pole, an overhead rain hood or shoulder-mounted equipment can change the antenna’s immediate environment. These small interferences, which are unlikely to occur on sunny days, tend to accumulate during rainy conditions.

In addition, in rainy weather the frequency of wiping equipment during observations increases, but you must be careful about how you wipe. Wiping roughly and shifting the antenna’s position, or merely smearing surface dirt with a wet cloth, can actually make the condition worse. On site, the basic practice is to keep the area around the antenna as close to its natural state as possible: gently blot moisture with a soft cloth, remove foreign matter first when mud is present, and avoid sticking anything unnecessary to the surface.

To address this factor, it is important not to over-rely on rain protection measures. Waterproofing is effective for protecting equipment, but it is a separate matter from guaranteeing reception quality. Incorporate a check of the antenna surface condition into your work routine; simply giving the surface a quick check for puddles or dirt before each observation can greatly affect stability. Rather than assuming light rain is nothing to worry about, it is important to recognize that reception conditions can change even in light rain.

Factor 2 Increase in multipath that tends to occur during rainy weather

The second factor is that multipath tends to increase on rainy days. Multipath is the phenomenon in which signals from satellites are reflected by buildings, the ground, vehicles, guardrails, temporary installations, slope protection works, wet wall surfaces, and the like, and arrive at the antenna via paths different from the direct wave. In high-precision RTK positioning, the effects of these reflections cannot be ignored, and special care is required during rainy weather.

The reason multipath tends to become a problem on rainy days is that the surface conditions around you change. Dry ground and wet ground have different reflection characteristics. When paved surfaces, steel plates, structural steel, retaining walls, bodies of heavy machinery, scaffolding materials, and the like get wet, the signal reflection conditions change and reflections with a greater impact than usual can occur. Even locations that did not show noticeable problems in clear weather can have unstable readings only on rainy days; in such cases, the cause may be the wet reflective surfaces.

Especially at sites in urban areas and around structures, reflections from wet man-made objects can be a greater practical problem than the rain itself. If guardrails beside roads, pavement with puddles, wet vehicle roofs, temporary fencing, or steel temporary construction materials are near the antenna, they can gradually affect the vertical direction more than the planar position. What is hard for operators to notice is not values that jump wildly, but a type of instability where the value differs slightly each time. This is a typical example of how, even when it appears to be Fix, repeatability becomes poor.

Also, on rainy days the sky becomes darker, reducing visibility and making it harder than usual to accurately judge your position at the observation point and the distances to surrounding obstacles. As a result, you are more likely to end up standing a little closer to a wall than usual, to take observations near a vehicle, or to measure right next to a materials storage area. This is also a contributing factor to increased multipath.

Even in forests and mountainous areas, on rainy days the wetting of trees and leaves easily alters signal reception conditions. In addition to the direct shielding by branches and foliage, reflections and scattering from wet leaf surfaces compound the effects, causing it to take longer than usual to obtain a fix and producing greater variations in quality depending on the location. At spots such as forest edges or the upper parts of slopes, where the sky is only barely visible, the difficulty of observation can increase sharply during rainy weather.

An effective measure against this factor is to check the surroundings of the observation point more carefully on rainy days. Even just looking within a radius of a few meters of where you set up the antenna to see whether there are wet metal objects, vehicles, puddles, or easily reflective walls makes a difference. Often simply shifting the position slightly will improve things, and on rainy days the choice of observation point tends to have a more direct impact on the results than on clear days.

Furthermore, it is important to implement procedures that verify measurements multiple times using known points and checkpoints. Because multipath effects can appear mixed in with fixed solutions that seem normal at first glance, it is essential not to rely on a single observation result. Especially on rainy days, you should not stop after obtaining a fix once; wait and reobserve after some time to check for repeatability.

Factor 3: Instability of Correction Information Caused by Degraded Communication Conditions

The third factor is that deterioration of the communication environment can make correction information unstable. When using network RTK, the rover must continuously receive correction information via a communication link. Therefore, not only satellite reception but also the stability of the communications is a prerequisite for maintaining accuracy. On rainy days, unexpected problems are more likely to occur on the communications side.

Generally, rainfall alone does not necessarily cause a significant deterioration in mobile communications, but at worksites conditions that make communication failures more likely tend to coincide during rainy weather. For example, the sky darkens and workers put devices into waterproof cases, making it difficult to check signal status; wet hands make operation harder; and sluggish screen responsiveness can delay noticing connection errors. In addition, in mountainous areas, development sites, or locations with many temporary structures, there are places that are inherently prone to unstable communications, and on rainy days that instability can become more pronounced.

If correction information is intermittently cut off, maintaining a Fix becomes difficult; the solution may fall to Float or require reinitialization. What is frightening in this situation is that the operator may continue observations without noticing the changes in status displayed on the screen. In particular, when rushing to work while avoiding rain, quality checks for each measurement tend to become sloppy, and unstable values immediately after a correction loss may be adopted.

Also, even if the communication link is established, high latency can cause an offset in the timing of correction updates, making results unstable during on-the-move or continuous observations. While it is still relatively easy to cope when carefully observing one point at a time while stationary, in situations such as guidance tasks, positioning, navigation, or continuous data acquisition, subtle communication delays affect both usability and reliability.

Even when operating a wireless reference station, there are additional considerations on rainy days. If the antenna connection is not sufficiently waterproofed, communication quality can deteriorate even though the equipment itself is functioning. If water reaches the connector, the cable routing puts undue strain on the cables, or the waterproof cap is not tightened properly, symptoms may appear only during rainy weather. Equipment that showed no problems on sunny days cannot be assumed safe if a rain-condition reproduction test has not been performed.

As a countermeasure against this factor, it is essential to regularly check the communication status using numerical indicators or icons. It is important not only to check whether a connection is active, but also to monitor the continuity of correction reception, the update interval, the Fix retention time, and whether reconnections occur. Also, depending on the site, it is effective to identify locations with weak communication before starting observations and, in those areas, change the observation order, prepare alternative measures, or first complete only the known-point checks.

On rainy days, not only equipment performance but also the quality of checks determines the outcome. Let go of the assumption that communications are necessarily functioning, and monitor system status more carefully than usual — it’s the quickest way to prevent accuracy degradation.

Factor 4: Errors Caused by Deterioration of Underfoot Conditions and Changes in Equipment Orientation

The fourth factor is errors caused by deteriorating footing and changes in the equipment's orientation. This is a highly practical and easily overlooked issue for RTK operations on rainy days. People tend to focus mainly on satellites and communications, but in the field physical changes—such as the pole tilting slightly, the tripod sinking, or the setup position shifting subtly—directly affect positioning results.

To measure a single point correctly with RTK, the position of the antenna center must be clearly defined, and the relationship between that position and the observation point on the ground must be stable. However, on rainy days the stability of the pole or tripod is reduced by mud, slippery pavement, settling of crushed stone, softening of slopes, puddles, and mud adhering to equipment. Even if it appears to be standing, a shift of a few millimeters to a few centimeters during the observation will directly become a positioning error.

Especially during pole observations, when the operator puts on rainwear and ends up holding a device in one hand and the pole in the other, maintaining verticality tends to become sloppy. Adopting a posture to avoid the rain, worrying about the ground and having unstable footing, and trying to finish the observation quickly—unfavorable conditions accumulate more than usual. Even if a bubble level is attached, raindrops make it hard to see, it’s dark and difficult to check, and the number of times the operator looks at it decreases; for these reasons, tilt control tends to become lax.

Also, observations using a tripod require caution. On soft ground or embankments, the tripod feet can slowly sink, and although there may be no problem immediately after setup, the orientation can change slightly after a few minutes. On rainy days this change tends to be larger, and it cannot be ignored, especially when installing a reference station on a known point or during longer static observations. The legs can sink without the operator noticing, introducing a systematic bias into the entire set of observation results.

Moreover, mud on the soles of your shoes can make your standing position at the survey point unstable. Even if you intend to place the tip of the pole exactly on stake heads, boundary markers, nails, or marking positions, you may shift slightly while trying to avoid slipping. This is not a satellite reception issue but simply a problem of setup positioning; however, looking only at the results it can appear as an RTK error. On rainy days, not only does instrument accuracy decline, but the accuracy of human setup drops as well.

With respect to this factor, mechanical stability should be emphasized as much as in rainy conditions. For pole observations, rather than trying to finish quickly, it is important to take a moment to verify verticality. When setting up a tripod, you are required not to omit checking for leg sinking, readjusting the legs, and re-checking the level. On poor ground, assume changes in the setup's attitude during the observation period, and, if necessary, reconsider the choice of the observation point itself.

On site, it is often dismissed as unavoidable because of the rain, but deterioration of underfoot conditions is one of the most reproducible sources of error. Precisely because many measures can be taken, it is a point that should be reliably controlled in operations.

Factor 5 Decline in Task Decision-Making and Verification Quality

The fifth factor is that rain degrades operational decision-making and verification quality. This, apart from equipment performance, may be the factor that creates the biggest differences on site on rainy days. RTK accuracy is not something the machine automatically guarantees; ultimately it depends on how appropriately people make decisions and perform verifications. On rainy days, the quality of these decisions tends to decline.

For example, because you don't want to get wet, want to finish quickly, find the screen hard to see, have difficulty operating with gloves or rain gear, or find it hard to leave records on paper, you may skip items you would normally check. Continuously confirming the Fix status, cross-checking with known points, rechecking antenna height, re-observing, recording observation times, and checking the coordinate system—each is a small procedure, but omitting them removes the support for accuracy.

What is particularly dangerous is the mindset that some deviation is inevitable because conditions are poor today. Once that way of thinking takes hold, values that would normally be redone tend to be accepted as they are. However, in practice, a single compromise on a rainy day can lead to major rework in later stages. In tasks such as as-built control, setting out, temporary works layout, boundary verification, and construction records, there are many situations on site where a tolerance of several centimeters (a few in) is not acceptable, and weather cannot be used as an excuse.

Also, during rainy weather the quality of record keeping tends to decline. If you don't record when and under what conditions the observation was made, whether it was Fix or Float, how it compared to known points, and whether it was re-observed, you won't be able to verify the results later.

Things you might notice and review on the spot on a clear day can be overlooked in favor of packing up on a rainy day, causing problems to emerge later. If the observation notes are insufficient in such cases, it takes time to determine the cause.

Furthermore, when working with multiple people, communication lapses are more likely to occur. If the sound of the rain makes it hard to hear, cold-weather clothing or hoods make it hard to see the surroundings, or there is an atmosphere of wanting to finish quickly, confirmation and double-checking become less effective. Misreading antenna height, mixing up observation point numbers, skipping survey points, and forgetting to re-observe are among the human errors that also increase on rainy days.

The way to address this factor is to have verification rules specifically for rainy days. For example, requiring known-point matching, checking the Fix duration for each observation, observing important points twice, treating height values especially carefully when conditions are poor, and always leaving records on site — mechanisms that do not leave decisions to individual judgment are effective. The drop in accuracy on rainy days is not only a matter of the equipment but also because the density of checks decreases. That is precisely why operational rules are effective.

Practical measures for using RTK on rainy days

As we have seen so far, the issues that cause problems for RTK on rainy days involve multiple factors: signal reception, signal reflections, communications, equipment orientation, and human verification actions. Therefore, a single countermeasure is not enough. On-site, it is necessary to consider a set of basic practical measures that must be observed precisely because it is raining.

First and foremost is the verification of known points before starting observations. It is important even in clear weather, but its priority increases in rainy conditions. By first checking values at known points or reliable checkpoints, you can quickly grasp how severe that day's observation conditions are. If there are signs such as large discrepancies with the known points, poor repeatability, or a long time to obtain a Fix, you can decide to switch that day's operations to a cautious mode.

Next, it is important to be stricter than usual when choosing observation points. On rainy days, simply avoiding spots with a somewhat restricted sky view, locations near wet structures, beside puddles, and close to vehicles or materials will help stabilize results. Places that posed no problem on sunny days should be assumed to have worsened conditions in the rain. You should prioritize good overhead sky visibility and minimal surrounding reflections over ease of observation.

Also, it's important not to finalize critical points based on a single attempt. Rather than measuring once and stopping, wait and re-observe, approach from a different direction and re-set, and, if necessary, verify at another check point—these steps make it easier to detect incidental errors. In work where height is especially important, exercise greater caution in rainy conditions than you would for planimetric measurements. Even if the numbers seem to match, if reproducibility is low you should decide not to adopt them.

In terms of equipment, making moisture control of antenna surfaces and connection points a routine is effective. Even if it is difficult to keep them completely dry, simply checking regularly whether water has pooled, mud has adhered, or there are any abnormalities at the connectors can reduce unexplained instability. The same applies to the fastening of poles and tripods; it is important to be mindful of checking them not only before observations but also during them.

In terms of communications, it is desirable to have a system that always allows confirmation that correction reception is stable. Even when the screen is hard to see, operational measures such as checking the status display before important measurement points, changing the work order in places with weak communications, and treating observations immediately after reconnection with caution are effective. Being prepared to suspect a communications cause immediately when a problem occurs can reduce unnecessary re-observations.

Furthermore, it is important for the team to share the policy of prioritizing quality assurance over work speed on rainy days. The more you rush, the more checks get missed, and as a result the number of reworks increases. You need the mindset to switch the plan itself to a rainy-weather mode—such as reducing the number of observation points from the outset, setting priorities, or waiting for the right conditions for only the critical points.

How to distinguish rain that is okay to continue working in from rain that should prompt you to consider stopping work

RTK can be used on rainy days, but you cannot carry out operations the same way in all types of rain. In practice, it is important to distinguish between rain in which work can continue and rain that should prompt consideration of cancellation or postponement. Decision criteria should consider not only simple rainfall amounts but also accuracy requirements, site conditions, the nature of the work, and the availability of alternatives.

Work is easiest to continue in cases of light or intermittent rain where overhead visibility is relatively good, there are few reflective objects nearby, communications are stable, and no problems have arisen with matching known points. Under such conditions, allowing a slightly longer observation time and incorporating re-observations can often be sufficient. On sites with stable footing, such as paved or developed areas, operations tend to be relatively easy to manage even in rainy weather.

On the other hand, situations in which cancellation or postponement should be considered include heavy rain that makes visibility poor, strong winds that make holding the pole difficult, ground so muddy that installation stability cannot be ensured, numerous wet reflective objects in the vicinity, intermittent communication dropouts, and inability to reconcile with known points. In particular, for tasks that require high reliability—such as staking out the positions of critical structures or verifying as-built conditions—the risks of forcing continuation are substantial.

Also, it is important to judge not whether an observation value is simply available, but whether that value can be explained. Values obtained during rainy conditions are easier to accept if they are corroborated by matching to known points, reproducibility, persistence of a Fix, and observation records. Conversely, if numbers are produced but the explanatory basis is weak, using them in downstream processes is risky. Because RTK displays numerical values, it can give a false sense of security, but what matters is not the existence of numbers but the substantiation of their quality.

As a site supervisor, you must make decisions to ensure you secure only the reliable points rather than trying to finish everything on schedule during bad weather. Even if you don't need to halt all operations, flexible practices—such as narrowing the scope of RTK work, switching to mainly checking tasks, or treating measurements as provisional pending a re-survey on a later date—are realistic.

When deciding on rainy days, the important thing is not to think in a binary way of usable or not usable. You need staged judgments according to the required level of accuracy — for example, usable under certain conditions, usable if verification is strengthened, or certain critical points should be deferred. Keeping this perspective makes it easier to avoid both unwarranted continuation of work on site and excessive cancellations.

Summary

RTK can be used even on rainy days. However, if you treat rainy conditions the same way as clear weather, it can lead to unexpected accuracy degradation and operational errors. The important thing is not to view rain itself as the only problem, but to consider the whole picture — including reception conditions, surrounding reflections, communication status, equipment orientation, and the quality of operational decisions that change because of the rain.

The five factors of accuracy degradation introduced here were changes in reception conditions due to raindrops and water films, increased multipath from wet surrounding objects, instability in the communication environment, changes in the orientation of poles and tripods caused by worsening footing, and a decline in the quality of human verification. None of these alone necessarily produces large errors, but on rainy days they tend to overlap, so accuracy is likely to become unstable as a result.

Therefore, in RTK operations during rainy conditions, basic actions such as confirming known points, selecting observation points, re-observing, monitoring communications, checking equipment condition, and thorough record-keeping become more important than usual. Do not be reassured solely by whether you have a Fix; it is essential to discern whether that Fix can be trusted.

On rainy days at a site, practical skill lies not in whether something can be used, but in determining under which conditions it can be used and to what extent it can be trusted. The worse the weather, the more necessary it is to adopt an operational approach to maintain accuracy rather than simply relying on equipment. If you want to use RTK stably, don’t judge based only on successful experiences in clear weather; it’s important to identify in advance the error factors and countermeasures for rainy conditions. By doing so, you will be able to make reproducible positioning decisions on site without being swayed by changes in the weather.