RTK GPS (Real-Time Kinematic GPS) has revolutionized race management in the America’s Cup and now the previously unprecedented accuracy is coming to amateur racing. While GPS technology has been around since the 1970s, its use was initially restricted to military applications, and civilian users had to deal with a deliberately degraded accuracy of around 100 meters. It wasn’t until Selective Availability was disabled in 2000 that civilian GPS reached an average accuracy of about five meters.
However, even today’s L1/L5 GPS accuracy—which under ideal conditions can only place you somewhere within a 2m (7ft) circle—remains insufficient for highly demanding applications like automating OCS calls. RTK GPS technology addresses this gap by offering accuracy of 1.8cm (or less) transforming how races are managed and ensuring sailors can make data-driven decisions with confidence.
This level of accuracy allows race committees to confidently automate OCS calls, set accurate race courses and potentially remove subjectivity from protest hearings, enhancing both the fairness and safety of the competition. The integration of RTK GPS into sailboat racing and management systems represents a leap forward, optimizing race performance and providing a reliable foundation for cutting-edge innovations in competitive sailing.
RTK GPS uses a technique that enhances the accuracy of standard GPS by incorporating real-time corrections from a fixed reference station or network of stations. Here's a breakdown of how RTK GPS corrections work:
1. Standard GPS Limitations
Standard GPS provides positioning data using signals from satellites orbiting the Earth. While useful for general navigation, standard GPS is limited in accuracy due to several factors:
- Ionospheric and Tropospheric Delays: GPS signals travel through the Earth's atmosphere, which can distort their path.
- Satellite Clock Errors: Small errors in the timing of satellite clocks affect positioning.
- Multipath Errors: GPS signals may reflect off surfaces like water, masts, carbon fiber sails, or standing rigging, which can cause inaccuracies.
This results in a typical accuracy which is not suitable for precision applications like autonomous vehicles, precision agriculture, or sailing race management.
2. RTK GPS Overview
RTK GPS enhances this basic GPS positioning by correcting errors in real-time. It works by using differential positioning with two GPS receivers:
- A Base Station at a known, fixed location.
- A Rover (the mobile GPS receiver), such as the one on a boat or a mark.
Velocitek LIVE Base Station
3. How RTK Works
Here’s the step-by-step process:
- Base Station Data: The base station is set up in a relatively stable environment within 12 km of the race course. This can either be on land or on a race committee boat.. The base continuously receives signals from GPS satellites and compares the calculated position (based on satellite signals) with its known position.
- Error Calculation: The base station detects the errors in the satellite signals that affect GPS accuracy, such as atmospheric distortion, satellite clock drift, and other sources of noise.
- Correction Signals: The base station calculates the difference (error) between the known position and the GPS-calculated position. It then transmits correction data (real-time corrections) to the rover, which in our case is a racing yacht.
- Rover Receives Corrections: The rover, which is in motion receives both the standard GPS signals from the satellites as well as the correction signals from the base station either via cellular networks and the internet, or a more local radio signal.
- Precise Positioning: The rover then applies these corrections to its own GPS data, allowing it to determine its position with centimeter-level accuracy, instead of the typical 2-meter. The result is far more accurate than what standalone GPS can provide.
4. Carrier-Phase Positioning
RTK GPS achieves high accuracy by not only using the GPS signals’ travel time but also by using the carrier phase of the satellite signals. Here’s how:
- GPS signals consist of a carrier wave and code. Standard GPS measures the distance to satellites by analyzing the code, which is accurate to a few meters.
- RTK GPS measures the phase of the carrier wave (a much shorter wavelength than the code) to calculate distance much more precisely.
By using the carrier phase, RTK GPS can resolve distances down to the centimeter level, as it can measure fractions of the wavelength of the signal.
5. Applications in Racing
In sailboat racing, RTK GPS is valuable because it provides:
- Precise Course Setting: Accurate positioning of buoys (and racecourse boundaries).
- Real-Time Tracking: The race committee and competitors can track positions with centimeter-level accuracy, ensuring fairness and safety.
- Improved Start/Finish Line Accuracy: With RTK GPS, the exact positioning of start and finish lines, and the competitors positions, globally and relative to the start and finish lines, can be managed accurately, reducing ambiguity during race events.
The real-time corrections make RTK GPS indispensable for applications that require pinpoint accuracy, transforming how race management and sailing tactics are handled.
RTK GPS was first used in the 34th America’s Cup by legendary navigator and technologist Stan Honey to revolutionize race management and broadcasting. While RTK GPS has become standard in elite events like SailGP, Velocitek LIVE brings this game-changing technology to a broader range of racing fleets, making high-accuracy race management accessible to everyone.
Contact us today to learn more about how Velocitek LIVE can revolutionize race management for your next regatta.