What It Really Takes
Autonomous robots, precision agriculture equipment, material-handling systems and other high-precision applications increasingly depend on GNSS for much more than approximate location. They need reliable positioning accurate enough to navigate, operate and repeat tasks consistently.
But achieving centimeter-level positioning is not simply a matter of adding a correction service to a conventional GNSS design.
High-precision GNSS requires the antenna, RF integration, receiver and correction architecture to work together as a complete system. High-precision positioning architectures combine GNSS signals, high-quality antennas, carrier-phase positioning techniques and correction data to achieve the required performance.
Start With the Application Requirements
Before choosing an antenna, receiver or correction service, define exactly what the application needs.
Centimeter-level accuracy may be essential for one application, while decimeter-level accuracy may be sufficient for another. Likewise, an autonomous machine operating primarily under open sky presents a very different GNSS environment from a robot working around buildings, trees and other obstructions.
Key requirements to consider include:
- Required horizontal and vertical positioning accuracy
- Operating environment
- GNSS antenna orientation during operation
- Static versus dynamic operation
- Mechanical and dimensional constraints
- Availability of cellular or internet connectivity
- Power consumption and cost
- Required positioning availability and reliability
These requirements provide the foundation for selecting the antenna, receiver and correction architecture.
Step 1: Select the Right GNSS Antenna
High-precision positioning starts with good GNSS signal reception.
Correction data can reduce several GNSS error sources, but it cannot replace good RF design. Poor satellite visibility, severe multipath, RF interference or inadequate antenna performance can still limit the accuracy and availability of the final positioning solution.
For high-precision GNSS applications, antenna selection should consider:
- Supported GNSS frequencies and constellations
- Single-band versus multi-band operation
- Radiation pattern and satellite coverage
- Gain and efficiency
- Circular polarization and axial ratio
- Multipath performance
- Phase-center stability
- Active versus passive architecture
- Available ground plane
- Mechanical and environmental requirements
Phase-center stability is particularly important for carrier-phase positioning. High-precision GNSS antenna designs aim to minimize phase-center variation and multipath effects to improve carrier-phase measurements and the resulting RTK position solution.
Consider Antenna Orientation, Not Just Platform Movement
Mobile platforms highlight why antenna selection needs to consider the complete application.
A robot that changes direction, for example, does not automatically require an omnidirectional GNSS antenna. What matters is how the antenna itself is oriented relative to the sky throughout the operating cycle.
A consistently sky-facing installation can favor an antenna optimized for upper-hemisphere GNSS coverage. Applications where antenna orientation varies significantly may benefit from broader coverage.
The appropriate antenna should therefore be selected based on the actual installation, required satellite coverage and operating environment, then verified on the finished platform.
Step 2: Get the Antenna Integration Right
Selecting the right antenna is only part of the challenge. Its performance needs to translate successfully into the final device.
Antenna integration should be considered early in the product-development process, not as a final-stage activity. Antenna placement and orientation, surrounding materials, available ground plane, cables and connectors, and the overall RF environment of the device can all influence the final implementation.
Designers should also consider the electronic environment within the product and validate the GNSS system in its final operating configuration.
Multipath is particularly important. Reflected satellite signals from buildings and other structures can degrade positioning accuracy.
Signal-quality indicators such as C/N₀ can be useful during validation, but they need to be considered alongside satellite availability, positioning fix status, convergence time and, most importantly, measured positioning accuracy under representative operating conditions.
A good antenna specification alone does not guarantee a good positioning solution.
Step 3: Select the Right High-Precision GNSS Receiver
The receiver is another critical element of the positioning architecture.
For centimeter-level RTK positioning, the receiver needs to process carrier-phase measurements and suitable correction data. Unlike conventional code-based GNSS positioning, RTK uses the phase of the GNSS carrier signal and integer ambiguity resolution to enable centimeter-level positioning.
Depending on the application, receiver selection may need to consider:
- Supported GNSS constellations and frequencies
- Multi-frequency capability
- Carrier-phase measurement capability
- RTK support
- PPP and PPP-RTK capability
- Galileo High Accuracy Service compatibility
- Supported correction-data interfaces
- Position update requirements
- Convergence and reacquisition performance
- Power consumption
- Interference, jamming and spoofing resilience
The receiver and correction architecture should be selected together because receiver capabilities determine which correction techniques and services the system can use.
Step 4: Choose the Right Correction Architecture
Standalone GNSS normally provides meter-level positioning, with actual performance affected by factors including satellite geometry, signal blockage, atmospheric conditions and receiver design. GPS-enabled smartphones are typically accurate to approximately 4.9 m under open sky, and performance can deteriorate around buildings, bridges and trees.
High-precision positioning uses additional correction information and positioning techniques to reduce GNSS errors. But no single correction architecture is right for every application.
RTK and Network RTK
Real-Time Kinematic, or RTK, is a positioning technique rather than simply a subscription correction service.
RTK combines carrier-phase GNSS measurements with correction data from a reference station. Network RTK extends the concept using a network of reference stations. With suitable corrections and operating conditions, RTK can deliver centimeter-level positioning.
This can make RTK particularly attractive for applications requiring rapid centimeter-level positioning where the necessary reference infrastructure and correction-data connectivity are available.
Precise Point Positioning
Precise Point Positioning, or PPP, uses precise satellite orbit, clock and bias information to improve positioning without requiring a nearby reference station.
This makes PPP attractive for wide-area applications, but accuracy and convergence performance depend on the correction service, receiver and implementation.
PPP-RTK
PPP-RTK combines characteristics of PPP and RTK, using wide-area correction information together with carrier-phase positioning techniques. It is designed to deliver faster high-precision positioning than traditional PPP approaches, while actual performance depends on the service and implementation.
Galileo High Accuracy Service
Galileo High Accuracy Service provides high-accuracy correction data free of charge. Corrections can be delivered through the Galileo E6-B signal or through an internet interface, and the user equipment applies the corrections through a PPP algorithm to produce the high-accuracy positioning solution.
The service is described as delivering horizontal accuracy down to approximately 20 cm and vertical accuracy of 40 cm under its specified service conditions.
Galileo HAS can therefore be an attractive option for applications requiring substantially better performance than standalone GNSS, but it should not be viewed as a direct substitute for RTK when centimeter-level positioning is required.
Match the Correction Approach to the Application
Instead of simply asking, “Which correction service provides the highest accuracy?”, designers should ask:
“Which positioning and correction architecture best meets the requirements of this application?”
The decision should consider:
- Required accuracy and convergence time
- Geographic coverage
- Available connectivity
- Availability of reference-station infrastructure
- Receiver compatibility
- Cost
- Application dynamics and operating environment
For some applications, fast convergence to centimeter-level positioning will be critical. For others, wide-area coverage, infrastructure independence, connectivity or cost may be more important. This is why the receiver and correction architecture need to be considered together.
Corrections Cannot Solve Every GNSS Problem
Understanding what correction data cannot fix is just as important as understanding what it can.
GNSS positioning errors include satellite clock and orbit errors as well as atmospheric effects. Correction systems provide information that allows compatible positioning engines to reduce the impact of relevant errors.
But correction data does not replace good antenna design or RF integration. Satellite blockage, severe local multipath and RF interference can still degrade the signals reaching the receiver.
Simply increasing antenna gain is therefore not a universal solution. Radiation characteristics, satellite coverage, phase-center stability, multipath performance, integration and receiver performance all contribute to the final positioning result.
Step 5: Validate the Complete System
Ultimately, GNSS performance must be demonstrated on the finished product.
Testing an antenna independently, confirming that a receiver supports RTK and obtaining correction data do not individually prove that the final product will achieve its positioning target.
The complete system needs to be evaluated in its final configuration and under operating conditions representative of the actual application.
The objective is not simply to demonstrate good individual component performance. It is to verify that the complete product meets its required positioning accuracy, availability and operational performance.
How Taoglas Can Help
Taoglas offers a broad portfolio of GNSS antenna technologies together with engineering resources to help engineers identify, integrate and validate suitable antennas for different applications. The Taoglas AI Antenna Recommendation Engine can help narrow antenna choices based on application requirements, providing a starting point for antenna selection.
But selecting the antenna is only the beginning. For high-precision positioning, careful integration and final system validation are critical for determining whether component-level capability translates into the required real-world positioning performance.
The Bottom Line
Achieving centimeter-level GNSS positioning requires more than adding a correction service or selecting a high-performance receiver.
It requires a system-level approach:
- Define the application’s positioning and operating requirements.
- Select the right GNSS antenna, paying particular attention to frequency coverage, radiation characteristics, multipath performance and phase-center stability.
- Integrate the antenna correctly into the final platform.
- Select the GNSS receiver and correction architecture together.
- Test and validate the complete positioning system under representative operating conditions.
RTK can enable centimeter-level positioning when carrier-phase measurements and appropriate correction data are available. PPP and PPP-RTK offer alternative architectures with different coverage and convergence characteristics, while Galileo HAS provides a free high-accuracy option targeting approximately 20 cm horizontal and 40 cm vertical accuracy.
The key is to treat high-precision GNSS as one complete system. The antenna, RF integration, receiver, correction architecture and operating environment must all work together to deliver reliable real-world positioning performance.
Technical References
- GPS.gov, “GPS Accuracy”: https://www.gps.gov/gps-accuracy
- u-blox, “Real-Time Kinematic (RTK) and GNSS Corrections”: https://www.u-blox.com/en/technologies/rtk-real-time-kinematic
- u-blox, “High Precision Positioning”: https://www.u-blox.com/en/technologies/high-precision-positioning
- European GNSS Service Centre, “Galileo High Accuracy Service”: https://www.gsc-europa.eu/galileo/services/galileo-high-accuracy-service-has
- ESA, “New Galileo Service Set to Deliver 20 cm Accuracy”: https://www.esa.int/Applications/Satellite_navigation/New_Galileo_service_set_to_deliver_20_cm_accuracy
- NovAtel, “VEXXIS GNSS-800 Series Antennas”: https://novatel.com/products/gps-gnss-antennas/vexxis-series-antennas/vexxis-gnss-800-series-antennas
- Taoglas, “Best Practices for GNSS Antenna Integration”: https://www.taoglas.com/blogs/best-practices-for-gnss-antenna-integration
- Taoglas, “AI Antenna Recommendation Engine”: https://www.taoglas.com/ai-product-recommendation-engine
