Can RTK Be Used Under Trees? 6 Countermeasures for Obstructed Environments

RTK is a convenient technology that can handle centimeter-level positioning information, but it may not provide the expected accuracy under trees. On site, problems such as "not fixing under the canopy," "position jitter," and "differences appearing on re-observation at the same location" tend to occur, and in practice, operating it with the same mindset as on flat or open areas often leads to failure.

That said, being under trees doesn't mean RTK is completely unusable. If you appropriately review canopy density, the surrounding terrain, observation time, equipment settings, and operational methods, there are plenty of situations where it can be used. The important thing is to understand what degrades accuracy under trees and, rather than forcing normal operating procedures, switch to observation procedures tailored to the obstructed environment.

In this article, after summarizing the reasons RTK becomes unstable beneath trees, we explain in detail six countermeasures that are easy to implement in obstructed environments. We also introduce how to distinguish situations under trees that are easy to deal with from those where it is better to consider alternative methods.

Table of Contents

• Can RTK be used under trees?

• Reasons why RTK accuracy tends to decrease under trees

• Measure 1: Choose a position that allows you to secure at least some sky visibility

• Countermeasure 2: Change observation procedures rather than being overly fixated on Fix

• Measure 3: Review observation time windows and seasonal conditions

• Measure 4: Prioritize stabilizing communications and corrections first

• Measure 5 Verify results by re-observation and checking known points

• Countermeasure 6: Avoid relying on RTK alone; combine it with other methods

• Situations where RTK is easy to use even under tree cover

• Situations where you want to prioritize non-RTK methods under tree cover

• Summary

Can RTK be used under trees?

In conclusion, RTK can sometimes be used under trees, but it is risky to expect the same stability and repeatability as in open areas. Under trees, signals from satellites can be weakened or reflected by leaves, branches, and trunks, making it difficult to maintain a Fix and causing not only horizontal accuracy but also vertical accuracy to become unstable.

One thing to be particularly careful about is that even if a measurement appears to have been obtained, the value is not necessarily truly reliable. While RTK offers the convenience of obtaining coordinates instantly, deterioration of the observation environment is immediately reflected in the positioning results. In obstructed environments such as inside forests or beneath street trees, you should not be reassured merely by a "Fix" indication on the display; it is essential to check the variability of the values and their reproducibility.

On the other hand, conditions under tree cover vary widely. In sparse woodlands where the sky is partially visible, on open work paths beneath branches, or in places where only the upper part of a slope is covered by canopy, RTK can be usable in practice by adjusting observation positions and rigorously following verification procedures. Conversely, in forests with dense stands of evergreen trees, in locations where valley terrain and canopy overlap, or on steep slopes where the sky appears very limited, it is often difficult to guarantee accuracy with RTK alone.

In other words, when using RTK under trees, the important thing is not to think in binary terms of "usable or unusable" but to determine "how reliable it can be in this environment." The measures for obstructed environments that follow will support that assessment.

Reasons RTK accuracy tends to degrade under tree cover

The reasons RTK accuracy degrades under trees can be broadly categorized into five: signal attenuation, multipath, degraded satellite geometry, unstable initialization, and reduced repeatability. These factors often overlap, and in the field they appear as combined causes rather than a single source.

The most common issue is radio wave attenuation. Because GNSS signals are very weak, reception can easily deteriorate due to moisture in leaves and branches and shielding by trunks. In particular, the effect tends to be stronger after rain, during periods of high humidity, and in seasons when foliage is dense. If you suddenly find it difficult to get a Fix in summer, the cause may be changes in foliage density or moisture content rather than a simple equipment failure.

Another problem is multipath. This is a phenomenon in which satellite signals are reflected by trees, the ground, nearby structures, and so on, and are received shifted relative to the direct wave. When multipath occurs, the receiver has difficulty determining the correct time of arrival, which leads to position jitter and altitude instability. This effect tends to be greater in locations where forest edges, trees, retaining walls, guardrails, vehicles, and similar objects are in close proximity.

Moreover, the degradation of satellite geometry cannot be overlooked. RTK uses signals from multiple satellites to obtain high-precision positions, but when the portion of sky visible is reduced by the tree canopy, not only does the number of usable satellites decrease, directional bias also occurs. In situations where only satellites near overhead can be picked up, or satellites in certain directions are almost entirely obscured, the geometry becomes unfavorable and the positioning solution becomes unstable.

Unstable initialization is also a problem peculiar to working under trees. Even in situations where you could obtain a Fix quickly in an open area, in obstructed environments the solution can remain in Float for a long time, or even revert to Float soon after achieving a Fix. If observations are made while the positioning status is unstable, people in the field may assume they have measured correctly, which can cause discrepancies to be discovered in later stages.

Finally, there is a decrease in reproducibility. This is very important. For example, if you measure the same point in the morning and in the afternoon, or reobserve it after a few minutes, large differences tend not to appear in open areas, whereas under trees it can shift by several centimeters or more. In other words, errors that went unnoticed in a single observation are more likely to become apparent when observations are separated in time.

In this way, under tree cover the weaknesses of RTK tend to manifest together. That's why simply using a high-performance receiver is insufficient; you need to optimize the entire field operation, including observation positions, procedures, and verification methods.

Measure 1: Choose a position where you can maintain at least some view of the sky

When using RTK beneath tree cover, the most effective measure is to choose a position that provides even a small amount of sky visibility. This may seem obvious, but in practice it is surprisingly often neglected. Rather than forcing a measurement directly over the target point, it is often more reliable to shift your position slightly to find a spot with a clearer view of the sky and, if necessary, use offsets or auxiliary procedures.

For example, beside a forest road, in a cutting on an access track, at a gap in the branches, near the shoulder of a slope, or on the side with a thinner canopy, reception can change significantly even with what looks like only a few steps' difference. On site, simply moving the receiver a short distance while it is set up and comparing the number of satellites, the ease of obtaining a Fix, and the stability of the position will make it much easier to find a favorable observation location.

The important point here is not to assume that making the observed target point and the receiver position coincide exactly is the only correct approach. In obstructed environments, insisting on the target point can yield only unstable values. It is more practical to determine a reference coordinate at a position where observations can be made stably, and then transfer that to the target point using a tape measure, a total station, offset functions, etc.

Also, the way the receiver is held and how the pole is set up affect measurements. If observations are made with the pole tilted, human error compounds the already unstable positioning under trees. Especially beneath tall trees, people tend to unconsciously lose their posture while trying to see the sky, so it is necessary to check the pole bubble and maintain stillness more carefully than usual.

You should also check for surrounding reflective objects. Not only the trees themselves, but nearby chain-link fences, vehicles, temporary structures or materials, wet slope-protection materials, and building exterior walls can all cause multipath. At entrances to wooded areas or near material storage yards, focusing only on the effects of trees can lead you to overlook the true cause. Even if the view is somewhat open, a large number of reflectors means it is not necessarily a good observation point.

In practice, when you arrive on site, it’s important not to start measuring right away but to spend a few minutes comparing candidate observation points. This brief reconnaissance will greatly reduce subsequent re-measurements and return trips. In obstructed environments, it is not an exaggeration to say that the initial position determines the bulk of the accuracy.

Countermeasure 2 Change the observation procedure without being too fixated on Fix

A common mistake under trees is to think, "as long as it shows Fix, that's fine." However, in a obstructed environment, what matters more than the Fix indication itself is how stable it is after fixing and whether repeated observations return the same values. It is necessary to shift operations from merely chasing the display to verifying the reliability of the results.

First, be aware that you should avoid taking a single observation immediately after a Fix. In open areas a short observation may often be fine, but under trees the values at the moment of Fix are not necessarily stable. It is safer to remain still for at least several to ten or so seconds and confirm that the fluctuations have settled before making the observation. If the coordinate readout continues to fluctuate finely, you should lower your confidence in the observed value.

Another effective approach is to take multiple observations at the same point. Rather than measuring once and stopping, wait a short time and measure again to check whether the difference falls within an acceptable range. This reduces the risk of adopting an unstable result obtained by chance. Especially under trees, confirming reproducibility rather than relying on single measurements becomes the core of quality control.

Adjusting the observation sequence can also be effective. Before measuring points consecutively within a forest, it is often better to first stabilize the receiver in an open area or at known points, and then operate by entering the obstructed section; this can be more likely to succeed than attempting to initialize directly in the forest. Conversely, if you force continuous observations in the forest while the receiver's condition remains degraded, the quality of all points can deteriorate without you noticing.

Furthermore, it is important to decide in advance the criteria for judging that an observation is infeasible. For example, if you set conditions such as not obtaining a fix within a certain time, a re-observation difference exceeding a certain amount, or the difference from a known point exceeding the standard, on-site decisions will be less likely to fluctuate. In obstructed environments, the more you try to force completion on the spot, the greater the risk of bringing errors back.

To obtain stable positions under tree cover, it is important not to simply apply the short-term, one-off, or continuous observation approaches designed for normal environments. A Fix indication is only the starting line; only by introducing procedures to verify stability and repeatability from that point does the observation become usable in practical work.

Countermeasure 3 Review observation time periods and seasonal conditions

RTK under trees varies in difficulty not only by location but also by time of day and season. Even at the same spot, it is not uncommon for conditions to be relatively stable in the morning but make it difficult to obtain a fix in the afternoon, or for it to work in winter but be challenging in summer. Therefore, you need to consider not only the site conditions but also the timing of observations as part of your mitigation measures.

First, what deserves attention is the seasonal difference in foliage density. In areas with many deciduous trees, it is generally easier to secure a clear view of the sky and for reception to improve during the period when leaves have fallen. Conversely, from the fresh spring leaf flush through midsummer, leaves become denser and tend to hold more moisture, so conditions can deteriorate significantly even within the same stand of trees. Even at sites with past observation records, you should plan on the assumption that the difficulty will change with the seasons.

Next, wet conditions. During rain or just after rainfall, leaves and branches retain moisture, which tends to increase signal attenuation. Even locations that had been barely operable in clear weather can suddenly experience an unstable Fix in damp environments. In forest work the ground easily becomes muddy, affecting movement and equipment handling, so weather conditions affect not only accuracy but the overall quality of the work.

Regarding the time of day, changes in satellite geometry should not be overlooked. You cannot obtain positioning equally well at all times, and the visibility of usable satellites changes over time. In obstructed environments, because the satellites that are visible in the first place are limited, differences by time of day can have a greater effect than in open locations. At some sites, there may be tendencies such as being more stable in the morning or becoming extremely unstable during specific time periods.

Therefore, for important observations and initial site visits, trial observations conducted at staggered times are effective. Even brief observations at several different times make it easier to determine when that location is easiest to measure. In particular, at sites that are visited repeatedly, as this knowledge accumulates, the precision of work planning improves significantly.

We should also reconsider the practice of consolidating observations made under trees at the end of the day. When running behind and rushed, there is often insufficient time to wait for a fix or to carry out reobservations, which tends to lead to lapses in judgment. The more obstructed the environment, the safer it is to prioritize observations during time slots that allow sufficient leeway.

RTK may look like automated positioning, but in obstructed environments it is strongly affected by natural conditions. Precisely for that reason, designing the process to include when measurements are taken leads to more stable results.

Countermeasure 4: Prioritize Stabilizing Communications and Corrections

When RTK is unstable under tree cover, many people first suspect satellite reception alone. That is of course important, but in practice instability in communications and correction data often combine to make the situation worse. Especially in mountainous areas and along forest edges, not only the view of the sky but also cellular reception can vary greatly from one location to another.

RTK assumes that the rover (mobile station) can continuously receive high-precision correction information. However, under tree cover or in areas with complex terrain, communications can become intermittent and correction updates can become unstable. If satellite reception is also poor in this situation, problems such as failing to obtain a fix, being unable to maintain a fix even when obtained, or sudden jumps in the reported values are likely to occur.

Therefore, when you enter the site, it is important to first check the communication status and confirm whether you are in a location where corrections can be received stably. Even if reception is poor directly under trees, it may become stable if you move a short distance to the side of a forest road or to an open ridge. If you dismiss the issue as “that’s unavoidable in the woods” without checking communications, you may overlook problems that could be fixed.

Also, the placement of receivers and terminals is another point to review. Placing a communications device close to the ground or in a position shadowed by your body can make reception even worse. Under trees, people tend to focus only on satellite reception, but the communications side may also be obstructed. Even small details such as the device’s orientation, how it is held, and the connection method can affect stability.

You should also check the correction service’s coverage area and operating conditions in advance. Even if it works fine at your usual sites, corrections can become unstable in mountainous or forested areas. It is important to test not only whether you are within the communication range but also whether you can operate stably on site. Especially at a site you are visiting for the first time, rather than starting the actual observations immediately upon arrival, it is reassuring to verify the connection in both an open area and an obstructed area.

In addition, you should ensure that you can isolate faults on site. If you perform work without knowing whether the issue is with the satellite, the communications, or the receiver settings, your response will be ad hoc. By checking in order whether you can get a normal Fix in an open area, how the status changes with and without communications, and whether the values stabilize at known points, it becomes easier to isolate the cause.

In obstructed environments, RTK can only be achieved when both satellite reception and communication stability are present. When it comes to accuracy measures under tree canopy, attention tends to focus only on the antenna and sky visibility, but in practical work ensuring communication and correction services are in place is just as important.

Measure 5: Verify results by re-observation and checking known points

When using RTK under trees, the most indispensable quality-control measures are re-observation and known-point verification. In obstructed environments, values may appear plausible at first glance but can be offset from the true values. Therefore, rather than adopting the measured values as-is, you should verify them before use.

First, verifying known points is the basic step. If there are known points or reliable control points on site, it is effective to check them before starting work, during work, and, if possible, before finishing. This is especially true at sites with many observation points under trees, where changes in instrument condition or environmental conditions can go unnoticed; checks at known points act as a safety valve.

The purpose of verifying known points is not simply to check whether they match. It is meaningful to understand how much deviation might occur under the current site conditions. A known point that is fine in an open area can suddenly show poor repeatability when you move under tree cover. Therefore, if possible, having check points in conditions close to obstructions will make on-site judgments easier.

Next, re-observation is important. By measuring the same point at different times and checking how closely the results agree, you can detect instabilities that a single observation would not reveal. For example, if the first observation and the observation a few minutes later differ by several centimeters (several inches) or more, you might not want to accept that point based solely on the on-site RTK result. Conversely, if multiple measurements concur even under harsh conditions, the practical level of confidence increases.

What you need to be careful about here is not to adopt only convenient values. When the field is busy, people tend to accept the first seemingly good value and want to dismiss later observations that don't match as "just a bad one." However, in shielding environments, the variability itself is important information. The fact that values do not line up indicates that the reliability of that point is low.

Work records are also important. If you record the observation time, time to Fix, satellite conditions, re-observation differences, communication status, and characteristics of the surrounding environment, it will be easier to evaluate the results later. This is especially valuable in forested areas, where differences between locations can be large even within the same area, so it is worth keeping them as material for improving future work.

In RTK under trees, verification can be more important than the observations themselves. You need the ability to question results as much as the ability to measure. Not skipping re-observations and checks of known points is the shortest route to maintaining quality in obstructed environments.

Countermeasure 6: Don't rely on RTK alone—combine it with other methods

One of the most important principles when using RTK under tree canopy is not to over-rely on RTK alone. On site the system’s high mobility makes you want to complete the job with RTK if possible, but in obstructed environments the more you insist on standalone operation, the higher the accuracy risk becomes. The idea of combining it with other methods as needed will, as a result, improve both efficiency and quality.

A typical approach is to secure stable reference points in open areas and supplement the detailed work under tree cover with other methods. For example, you fix coordinates at intersections of forest or service roads, or at points with open sky, and then perform auxiliary surveying from those points to the target locations. This allows you to distinguish between places where RTK performs well and places where it struggles.

Also, depending on the target, it may not be necessary to directly acquire all points under trees as high-precision coordinates. By distinguishing between situations where a rough grasp of position is sufficient and those that require exact positions, you can reduce unnecessary observations. In obstructed environments, it is important to determine in advance which points require which level of accuracy.

Furthermore, combining multiple observations and verifications from different routes is also effective. If the same point can be confirmed from different vantage points, systematic errors are easier to detect. Because the conditions at each point within a forest differ, it can be difficult to make all points the same quality using only a single observation method.

In practice, it is important to determine the areas where RTK can be used and assign roles accordingly. Streamline work with RTK — acquiring reference points in open areas, mapping the backbone of movement routes, and positioning perimeters and entrances — and carefully address the most severely signal‑obstructed areas with separate procedures. With this approach, you can take advantage of RTK while making it easier to avoid accidents caused by environments in which it performs poorly.

What is truly required at sites under trees is not that everything can be done with RTK alone. It is the ability to decide which parts to process with RTK and where to switch to other methods to ensure the necessary quality. That flexibility becomes the most practical measure in obstructed environments.

Situations Where RTK Is Easy to Use Even Under Trees

Even under tree cover, there are situations in which RTK is relatively easy to use. For example, in sparse woodlands where the sky appears patchy, along work tracks or forest roads that have openings to the sky, at target points close to the forest edge, or where trees are tall but trunk spacing is wide and horizontal visibility exists. In such environments, provided observation positions are adjusted and re-observation is assumed, there is room for practical use.

Also, for tasks that do not demand extremely strict absolute accuracy, it becomes easier to use even under tree cover. For example, for rough position awareness, route confirmation, recording the positions of inspection targets, or positioning for progress management, it can be used with a different set of decision criteria than precise surveying results. However, even in these cases, it is a prerequisite to avoid ambiguity about the required accuracy and to make clear that it is suitable for the intended use.

Moreover, cases where only part of a site is under tree cover are also well suited to RTK. By efficiently surveying the largely open areas and addressing only the problematic points individually, you can maintain high overall productivity. On such sites, clarifying where and how to use RTK can yield significant benefits.

The important point is not to lump things together as “usable because it’s under trees” or “not usable.” Conditions can vary greatly even within the same site, and results can change just a few meters apart. First identify the conditions that are easy to work with, and then reliably build up results within that range.

Situations Where You Should Prioritize Non-RTK Methods Under Trees

On the other hand, there are situations where methods other than RTK should be prioritized. A typical example is places where the tree canopy is very dense and the portion of the sky that is visible is extremely limited. In stands of densely packed evergreen trees, deep in valleys, or where slopes and trees overlap and severely restrict the view, maintaining stable RTK operation can be difficult.

Also, pay special attention in situations where the reliability of height accuracy is particularly important. Under trees, height measurements tend to be less stable than horizontal measurements, and vertical offsets can occur even when things appear fine. If you need to handle height precisely, do not rely solely on RTK.

Boundary setting, as-built measurements, and structure installation are tasks where errors directly affect subsequent processes, so they require caution. In these situations, measuring correctly is more important than merely being able to measure. If there are concerns about reproducibility, it is safer to switch to an alternative method at that point.

Moreover, locations with unstable communications where maintaining correction information is difficult are also disadvantageous for RTK. In areas where not only satellite conditions but also communication conditions are poor, on-site trial and error tends to be prolonged, and as a result efficiency declines. In obstructed environments, it is important to choose methods that prioritize quality assurance rather than forcing conformity to RTK.

Summary

RTK can sometimes be used under trees, but it is a technology that, if used with the same mindset as in open areas, can easily cause poor accuracy and the need to remeasure. Under trees, signal attenuation, multipath, degraded satellite geometry, unstable initialization, and reduced repeatability tend to combine, and you cannot judge quality based solely on an indication that it is "Fix".

Therefore, in obstructed environments it is essential to operate with countermeasures in mind. First, as a basic measure choose a location that secures as much sky visibility as possible, and switch to an observation design that does not fixate too much on the target point. Next, rather than a one-shot observation immediately after Fix, incorporate stationary confirmation and multiple observations to assess the stability of the results. Furthermore, be mindful of the observation time of day, seasonal conditions, and moisture, and check the stability of communications and corrections in advance.

And above all, it is important to verify values through re-observation and checking known control points. Beneath tree canopy, there are situations where confirming is more important than measuring. If the results do not agree, it may be necessary to decide not to accept that point based solely on RTK. In practice, the most rational approach is to combine other methods as needed and to delineate the areas where RTK performs well from those where it does not.

The key to succeeding with RTK under trees is not to expect it to be universally applicable. By adjusting your position, procedures, and verification methods to suit the environment, there are certainly situations where it can be used. Conversely, in harsh conditions, recognizing the limits early is also part of quality control. In obstructed environments, not only the performance of the equipment but also the quality of field judgment determines the outcome. To use RTK with confidence, under trees it's important to structure operations based not on "can it get a fix?" but on "can it be used reliably?"