g Errors with your Equipment
High end antenna and receiver designs can access more signals and are equipped to reduce more challenging error sources such as multipath, receiver noise, and poor signal quality. Antenna selection is important. An antenna acts as a gatekeeper: the quality and design of the antenna directly impacts the quality of what goes into your GNSS position. Their design is critical for filtering out bad quality signals, and the design should be matched to the capabilities of the receiver.
But nothing impacts your performance quite like your antenna placement; antennas with a clear view of the sky are able to track much cleaner signals, which means higher quality input into your position calculations. Our Introduction to GNSS book details the different antennas beneficial in real-life scenarios, so download the book for further reading.
Choosing receivers and antennas that track multiple constellations directly impacts the quality of your position. Tracking multiple constellations increases the number of potential satellites you can position with. If a satellite moves out of sight, or goes offline, you have built-in redundancy by tracking other satellites. With access to multiple frequencies, your receiver has more information about each satellite, and can perform more comprehensive error and positioning models. It also builds in resiliency against interference if one frequency band is knocked out.
Equipment and algorithm designs play a fundamental role in how all of the information in the satellite signal is used; systems that can leverage more information are often able to recover from delays and outages, atmospheric errors, and multipath effects. All these factors contribute to having better quality data to work with and provide a more accurate and reliable position.
Reducing Errors with Corrections Services
Depending on your location and application, you may want to use correction services to further improve your position accuracy. Corrections deliver additional information about error sources, which your receiver uses to improve the quality of its GNSS position. This ultimately provides a more accurate and reliable solution.
The three commonly used correction services we’ll focus on here are: Satellite-Based Augmentation Systems, Real-Time Kinematic, and Precise Point Positioning.
How Corrections Services Work
By this point in our series, we’ve thoroughly discussed the basic relationship between GNSS satellites and transmission of data to user equipment. The signals travel from the satellites and are tracked by receivers on the ground. When a receiver is established on a fixed coordinate, this is called a base or reference station.
These base stations play a fundamental role in correction generation. First, we can get important information about error sources by comparing the measured base position against its known coordinate. Second, if you have many base stations, you can collect data across this network to get regional information and provide corrections over a large area.
Whether you’re using a single base station, or a network-based service, these corrections are delivered to the user’s equipment to improve the position accuracy.
Satellite-Based Augmentation System Corrections
Countries around the world have their own SBAS networks to supply corrections to regional users. As shown here, GNSS satellites are tracked by a network of reference stations on the ground, and this data is forwarded to a master station. The master station knows the coordinates of all the stations in the network, and so it computes corrections by comparing the measured positions to the known coordinates. This technique reduces atmospheric, satellite timing, and orbital errors.
The corrections are then uplinked to geo-stationary SBAS satellites and broadcasted back to SBAS-enabled receivers on the ground. The corrections are freely available to all users in the covered region, providing nearly immediate meter-level accuracy.
Real-Time Kinematic Corrections
RTK is a regional solution requiring a base station near to where