Even RTK Has Limits: What Affects Your Signal—and How to Get the Most from It
When it comes to precision positioning, Real-Time Kinematic (RTK) GPS is the gold standard. It can deliver centimeter-level accuracy in real time, and it's transformed how we map, survey, fly drones, and guide autonomous equipment. But for all its power, RTK still has limits.
Just because your gear is “RTK enabled” doesn’t mean you're guaranteed perfect results in every situation. Like any high-precision system, RTK performance depends on a mix of environmental and technical factors. If you’ve ever had a signal drop out, or noticed weird position jumps, it’s not always your equipment—it could be the sky.
Let’s break down the four major factors that impact your RTK signal—and how you can get ahead of them to avoid downtime and keep your data tight.
1. Satellite Count: More Isn’t Just Better, It’s Essential
RTK depends on GNSS satellites (not just GPS, but also Galileo, GLONASS, BeiDou, and others) to calculate your position accurately. But it needs multiple satellites—at least five, but preferably ten or more—with a clear view of the sky to resolve those centimeter-level measurements.
Fewer satellites = weaker geometry = more potential error.
This becomes especially problematic during certain times of day when the satellite constellation geometry is weak, or if your equipment is limited to fewer GNSS constellations. Modern multi-band, multi-constellation receivers help—but they still can’t see through mountains or metal roofs.
✅ Pro tip: Before a mission, check GNSS satellite availability using tools like Trimble Planning or GNSSPlanner. Schedule around low-visibility times when possible.
2. Ionospheric Interference: It’s All About the Space Weather
The ionosphere is a layer of charged particles high above the Earth’s surface—and GNSS signals must pass through it to reach your receiver. Solar activity, geomagnetic storms, and even sunrise/sunset transitions can all distort the signal as it travels.
These effects introduce delays and phase shifts that can cause your RTK corrections to degrade, especially if your base station is far away (more on that below).
The good news? Dual-frequency receivers can account for some ionospheric delay, and RTK correction networks often use models to help mitigate the issue. But during periods of high solar activity (like we’re seeing in the current solar cycle), even the best models can’t eliminate all of the distortion.
✅ Pro tip: Use real-time space weather monitors or correction network alerts to anticipate high-interference days. If you're noticing high latency or float solutions, this could be the culprit.
3. Obstructions: Trees, Buildings, and Terrain
GNSS signals are line-of-sight. That means anything between your receiver and the satellites can block, reflect, or distort the signal—this is called multipath.
Tall trees, metal buildings, bridges, mountains, and even nearby vehicles can mess with your signal quality. Worse yet, multipath can be sneaky—it doesn’t always cause a complete signal loss, but it can introduce enough error to ruin your accuracy without you realizing it.
This is especially critical for drone operators and surveyors working in urban environments or forested areas. RTK works best in open sky, not in the shadows of steel or spruce.
✅ Pro tip: Before you deploy, perform a quick sky visibility check. Many apps like GNSS View or Mission Planner offer real-time sky plots. Avoid placing a base station near vertical surfaces or under cover, and always keep your rover as exposed to the sky as possible.
4. Base Station Distance: The Farther You Are, the Less Accurate You Get
RTK corrections are transmitted from a known fixed base station to your rover unit. These corrections rely on the assumption that the errors observed at the base station are roughly the same at your rover. But as you get farther from the base, that assumption breaks down.
This is often called the baseline length—and the longer the baseline, the less accurate the corrections. Most RTK systems are rated for 20–30 km baselines, but the quality degrades gradually beyond that, especially under poor ionospheric conditions.
If you're using a virtual network or NTRIP service, the correction provider often selects a "nearest mount point" or constructs a virtual base to minimize this baseline distance. But if you're manually selecting a base or using your own, distance matters a lot.
✅ Pro tip: Always check your current baseline distance and correction latency in your receiver interface or control app. For best results, try to stay under 20 km from your correction source.
Wrapping Up: Know the Limits, Stay in Control
RTK is an incredibly powerful tool—but it’s not magic. By understanding the limits of your system and watching for these four key factors, you can troubleshoot problems before they derail your work.
Whether you're flying drones, staking out points, or guiding equipment, here’s the takeaway:
✅ Check your sky visibility.
✅ Monitor your satellite count.
✅ Watch your baseline distance.
✅ Keep an eye on correction latency.
✅ Stay aware of solar and space weather.
And when in doubt, take a few minutes to pause and review the data—not just the position output, but the signal diagnostics too. A quick check now could save you hours of rework later.
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