If you’ve ever used RTK (Real-Time Kinematic) GNSS for surveying, mapping, or precision agriculture, you’ve likely heard the term multipath. It’s one of those invisible problems that can make your receiver act like it’s had a few too many drinks—telling you you’re somewhere you’re definitely not.
In this post, we’ll break down exactly what multi-path is, why it messes with your RTK positioning, what causes it, and—most importantly—how modern RTK systems are designed to work around it.
Why Multipath is a Problem in RTK
The Future of Multipath Handling
Multipath is when a GNSS signal (like from a GPS, GLONASS, or Galileo satellite) doesn’t travel straight to your receiver but instead bounces off a nearby surface—like a building, tree, car, or even the ground—before it gets there.
That bounce adds extra distance to the signal’s journey. Since GNSS receivers rely on precise timing to calculate your position, even a tiny delay (a few nanoseconds) throws off the calculation. That means your receiver might think it’s in one location when it’s actually somewhere else. Not ideal if you’re trying to map a field edge, lay out a construction site, or collect survey data.
So, the term “multipath” refers to multiple paths the same satellite signal might take—some direct, some bounced—before reaching your receiver. These reflected signals can cause a lot of issues.
There are two broad categories of multipath sources: artificial (man-made) and natural. Let’s go over both.
1. Man-Made Sources
2. Natural Sources
Trees are the main source of multi-path interference you will encounter while in the field. There are two different main tree types that will interact with the signals differently.
The final source you should be aware of are bodies of water: Wet surfaces, especially when calm, can reflect signals. Ponds, lakes, even puddles near your survey site can contribute. This extends to icy conditions as well. In a rather infamous case, David and I were testing the tilt sensor on older equipment on a frozen parking lot we could not figure out why we were running into issues obtaining a reliable fix. It turned out as we tilted the pole we ran into issues where reflections off the ice in the parking lot were causing high levels of multi-path.
To understand the impact of multipath in RTK, you need to know how RTK works. You can check out our explainer on RTK here:
RTK uses satellite signals and correction data from a fixed base station to calculate your position in real time—down to the centimeter. The whole process relies on:
When a satellite signal gets reflected, the receiver may mistakenly treat the longer, indirect signal as legitimate. That corrupts the timing, throws off the phase calculation, and results in conflicting data when calculating the position. The receiver needs to have as direct a line of sight to the satellite as possible in order to obtain a fixed solution.
Here’s what that can look like:
That’s why older RTK devices—especially those from the 4th and 5th generation—struggled under trees or near buildings. They just couldn’t filter out the bad signals effectively or had limited access to satellite constellations. You can see the difference in our comparison of the 7th generation Hemisphere S631 to the 4th generation Hemisphere S320.
Let’s get this out of the way: you can’t eliminate multipath entirely.
You can’t bulldoze a building next to your job site. You (probably) shouldn’t cut down every tree in sight. And you can’t control the environment in most real-world scenarios.
So instead of trying to remove all the causes, the key is to understand how to work around them—either by changing your setup or using the latest equipment with all available satellite constellations.
Even though you can’t erase multipath, there are several ways to reduce its impact and make sure you can get your work done:
1. Use a Modern Receiver with Multi-Constellation Support
Older GNSS receivers might only track GPS or GPS + GLONASS. That means fewer satellites to work with—and a higher chance that the only available signals are reflected ones.
Modern receivers (like the Hemisphere S631, Trimble R12 or Leica GS18) can track:
More satellites = more direct paths to choose from = less reliance on possibly reflected signals.
When you’re under trees, next to buildings, or in any high-multipath environment, having access to all the constellations gives your RTK engine options. It can cherry-pick the cleanest signals for the job.
However, it is not just enough to ensure you see all of the latest signals, you also want to make sure your receiver can see all available signals. Many of the latest signals like GPS L5 and BeiDou B3 are designed to punch through tree canopies with more robust modulation and a higher broadcast power level.
2. Use an Advanced RTK Engine
The RTK engine is the brain of your receiver. It decides which signals to trust, which to reject, and how to combine them into a final position.
Basic RTK engines might just average everything together—which doesn’t work when you have corrupted multi-path signals in the mix. They only make it harder to calculate a final position.
Advanced engines (like Hemisphere’s Athena or Trimble’s models with ionospheric filtering) do a lot more:
In some cases, with a really good engine, you can even maintain centimeter-level fixes under a leafy canopy or in partially enclosed environments—something that was nearly impossible just a few years ago. However, different engines can produce different levels of performance in different environments. Check out our video series where we took the R12i, GS18 and GRx3/Hiper VR under trees.
3. Pay Attention to the Environment
Yes, the tech matters. But technique and awareness matter too.
If you’re running an RTK rover in the field, consider these practical tips (which are especially important for your base station setup):
– Avoid standing close to reflective surfaces (walls, cars, water).
– Watch the height of your receiver—higher positions can sometimes see more satellites with fewer obstructions.
– Use short observation windows in clean areas—move out from under trees to capture clean fixes, then return for measurements. By comparing fixes to one another that were captured at different times of the day can ensure your position is reliable. Check out our article and video on repeatability: How Repeatable is RTK GPS in The Real World?
As GNSS and RTK tech evolves, multipath is becoming more manageable. Here’s what’s helping:
Multipath is a fact of life in GNSS work, especially in RTK. It’s caused by reflections—usually from nearby surfaces—and leads to bad data if your receiver can’t handle it. While you can’t avoid multipath completely, you can work smarter:
If you’re still using older hardware—or struggling to get fixes near buildings or under trees—it might be time to upgrade. Multipath isn’t going away, but modern receivers are getting a whole lot better at dealing with it.
Multipath happens when satellite signals bounce off surfaces like buildings, cars, or trees before reaching your receiver. These bounced signals take longer to arrive, which throws off the receiver’s position calculation, leading to inaccurate results.
No. Multipath can’t be eliminated because you can’t control every surface around your job site. But you can reduce its impact by using modern receivers, avoiding reflective environments, and adjusting your survey technique.
Different GNSS signal frequencies reflect differently. By comparing how the same signal behaves across L1, L2, and L5 bands, modern RTK engines can better identify and isolate clean, direct signals from reflected ones, improving position accuracy.
They use multi-constellation support (GPS, GLONASS, Galileo, BeiDou), track more frequencies (like L5 and B3), and include advanced RTK engines that filter, downweight, or reject reflected signals. Some even use machine learning to identify patterns of multipath interference.
Older receivers often lack support for newer constellations and frequencies. They also use less sophisticated RTK engines, which can’t properly filter out corrupted signals. As a result, they struggle to maintain fixed solutions near buildings, under trees, or around reflective surfaces.
Bench Mark Equipment & Supplies is your team to trust with all your surveying equipment. We have been providing high-quality surveying equipment to land surveyors, engineers, construction, airborne and resource professionals since 2002. This helps establish ourselves as the go-to team in Calgary, Canada, and the USA. Plus, we provide a wide selection of equipment, including global navigation satellite systems, RTK GPS equipment, GNSS receivers, and more. We strive to provide the highest level of customer care and service for everyone. To speak to one of our team today, call us at 403-286-0333 or email us at [email protected].
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