What is GPS RTK (Real-time Kinematic Positioning)?

RTK (Real-Time Kinematic) technology, initially developed for industrial applications, has found a new purpose in the lawn care industry, enhancing the accuracy and efficiency of autonomous mowers. This technology allows these machines to achieve centimeter-level accuracy in navigation, making it a critical component for smart lawnmowers like the ANTHBOT Genie. Such accuracy is especially important for tasks such as autonomous mowing, obstacle avoidance, and creating precise mowing patterns, ensuring that the lawn is perfectly trimmed without any missed spots.

In this blog, we’ll dive into the technical details of RTK, the differences between full-band and dual-band RTK systems, and how these technologies enhance the performance of robotic lawnmowers.

RTK in Robotic Lawn Mowers

The integration of RTK into robotic lawnmowers brings significant benefits to both consumers and manufacturers:

Enhanced Precision: RTK allows the mower to mow in complex patterns without missing spots, ensuring a more consistent cut and a healthier lawn.
Autonomy and Efficiency: The technology enables full autonomy, with mowers operating with minimal human intervention while navigating complex obstacles like trees, fences, and garden furniture.
Scalability: Full-band RTK systems are ideal for large residential properties, commercial lawns, and public spaces, where precise navigation and coverage are essential.

The use of RTK technology in robotic mowers significantly enhances their functionality, allowing them to operate autonomously with minimal supervision. This leads to better results and more efficient mowing operations, which ultimately saves time and effort for homeowners and businesses.

How RTK Works

RTK technology relies on a base station and a mobile receiver. The base station is a fixed unit located at a known, precise position, and it continuously measures the difference between its fixed position and the positions of satellites in the sky. The base station calculates the error in the satellite signal, then transmits correction data to the mobile receiver (mounted on the robotic lawnmower). This correction data improves the GPS accuracy, allowing the receiver to achieve centimeter-level precision.

Base Station Role: The base station is essential in RTK technology, as it provides the correction signals that improve the precision of the GPS system. Without the base station’s real-time correction, the positioning accuracy would be much lower, typically at meter-level precision.
Mobile Receiver Role: The mobile receiver on the robotic mower receives GPS signals from satellites and correction data from the base station, enabling it to adjust its position in real-time and navigate with high precision.

The base station essentially "corrects" the GPS signal errors caused by atmospheric conditions, satellite geometry, and other factors, enabling the mower to achieve much higher accuracy than standard GPS systems.

How Fast is RTK?

One of the standout features of RTK technology is its ability to provide high-precision positioning data in real-time. The speed at which RTK systems can update their position is crucial for maintaining smooth and accurate navigation, particularly in dynamic environments like lawns with obstacles.

Refresh Rate: Full-band RTK systems typically operate with a 50Hz refresh rate, meaning they update their positioning data 50 times per second. This high refresh rate ensures that the mower can make real-time adjustments as it navigates the lawn, reducing the likelihood of drift or boundary violations.
Dual-band RTK systems usually have a lower refresh rate of 5Hz, meaning they update the position data only 5 times per second. This slower update rate can result in delays and discrepancies between the mower’s actual location and the displayed position, especially in fast-moving or complex environments.

The fast refresh rate and accurate data provided by RTK systems allow robotic mowers to maintain their position even when navigating tight corners, avoiding obstacles, or working under varying environmental conditions.

RTK Technology: Full-band vs. Dual-band

RTK technology, at its core, utilizes satellite signals to improve the positioning accuracy of GPS systems. The technology is categorized into two types: Full-band RTK and Dual-band RTK. Each has its own capabilities and limitations, and understanding these differences is key to choosing the right solution for autonomous systems like robotic lawnmowers.

Full-band RTK

Multiple Satellite Systems: Full-band RTK receivers can receive signals from multiple satellite systems, such as GPS (U.S.), GLONASS (Russia), BeiDou (China), and Galileo (Europe). This broadens the global coverage and enhances the robustness of the system, allowing it to provide more stable positioning services across different regions and environments.
Higher Frequency and Robust Data Handling: A full-band RTK system can handle up to 6 satellites and 22 frequencies, with a baseband channel count of 1040. This enables the system to process data from multiple satellite constellations more effectively.
Fast Data Convergence: The full-band system operates with a 50Hz refresh rate, meaning it updates positioning data more frequently. This ensures that the mower's location data is accurate and up to date, reducing the chances of discrepancies during operation.
Advanced Features for Precision: Full-band RTK systems support features such as base station scoring, interference detection, environmental scoring, low-speed RTK, and transmission packet segmentation. These features allow the mower to evaluate whether its current position aligns with installation requirements and adjust its operation accordingly.

Dual-band RTK

Limited Satellite Coverage: Dual-band RTK systems are only capable of receiving signals from two fixed frequency bands. This limits their global coverage and can lead to situations where the mower cannot obtain a signal, especially in regions with fewer satellite systems.
Lower Frequency and Channel Count: A dual-band RTK system typically uses 4 satellites and 8 frequencies, with a baseband channel count of 135. This results in less efficient signal processing and lower accuracy compared to full-band systems.
Slower Data Convergence: Dual-band RTK systems operate at a 5Hz refresh rate, which means their signals refresh less frequently. This results in a slower convergence of positioning data, leading to potential delays and discrepancies between the actual location and the displayed position.
Increased Latency: Due to the slower refresh rate, dual-band systems can experience lag or offset in positioning data, making the system prone to errors, especially in dynamic environments where precision is essential.

How RTK Technology Sets the Genie Apart

At ANTHBOT, we’ve integrated a full-band RTK system into our Genie series lawnmowers, setting them apart from competitors that rely on dual-band RTK technology. Here are the key advantages of using full-band RTK in our Genie models:

Easier Signal Acquisition: Full-band RTK systems are more capable of acquiring signals across a broader spectrum of satellite systems. This provides more flexibility in choosing installation locations for the base station, allowing for better coverage even in challenging environments.
Better Precision and Real-time Performance: Full-band RTK technology ensures more accurate and real-time positioning data. This means the mower can navigate more precisely, avoiding issues like boundary violations and ensuring that its displayed position matches the actual location with minimal delay.

Real-world Testing: Genie vs. Competitor N

To highlight the practical benefits of full-band RTK, we conducted a series of tests comparing our Genie mower, equipped with full-band RTK, against a competitor's model (N), which uses a dual-band RTK system. These tests were conducted in several common mowing environments:

Under Trees
Under Roof Eaves
Rainy/Cloudy Days
Rainy/Cloudy Days with Roof Eaves
Rainy/Cloudy Days with Trees

Genie performed flawlessly across all test scenarios, maintaining accurate, real-time navigation without any significant drift or boundary violations.

On the other hand, Competitor N experienced frequent issues with signal loss, position drift, and even failure to operate. In some tests, the mower couldn’t recover for up to 10-15 minutes, or failed to work entirely. These discrepancies are mainly due to the limitations of dual-band RTK technology, which struggles in complex environments.

Learn more about how to install the Genie RTK system.

RTK in Other Industries

While RTK is widely recognized for its application in autonomous mowing, it has been successfully implemented in several other fields, such as:

Agriculture: RTK is used in precision farming to guide tractors and other farming equipment, ensuring that planting, fertilization, and harvesting are done with high accuracy, improving crop yield and reducing waste.
Surveying and Mapping: RTK provides the high precision necessary for land surveying, topographic mapping, and construction layout.
Autonomous Vehicles: RTK is essential for autonomous cars, drones, and other robotic systems, providing precise navigation for safe and efficient operation in dynamic environments.

To wrap up, RTK technology is a key factor in enhancing the performance of robotic lawnmowers, offering precise real-time positioning. Full-band RTK systems, like those in the ANTHBOT Genie, provide faster signal acquisition and higher accuracy compared to dual-band systems. This results in better reliability and smoother performance, even in challenging environments. With Genie’s full-band RTK, users can expect a consistent, efficient mowing experience, making it a standout choice in the market.