How to reduce GNSS & GPS errors - Intro to GNSS Episode 4 – Reducing GNSS Errors, Hexagon | NovAtel

How to reduce GNSS and GPS errors

Hexagon | NovAtel Corrections Services Product Manager Jennifer Busser explores the methods used to reduce GNSS errors in episode four of our on-demand webinar series. From equipment to additional services, these methods help your solution deliver a position you can trust. We cover more of these topics in our free book, an Introduction to GNSS: https://novatel.com/support/knowledge...

This is episode four of our introduction to GNSS webinar series exploring the foundations of GNSS positioning. In this episode, we’ll review the ways in which to reduce GNSS positioning errors.

Basic errors occur at all stages of GNSS positioning: clock and orbit errors are introduced at the satellite; the satellites’ signals are sped up or delayed as they move through the earth’s atmosphere; and as they get closer to the ground, they could reflect off buildings before finally getting to the antenna receiver.

You can reduce errors through your equipment environment through high quality antennas and receivers, as well as antenna placement. Equipment designed to connect to multiple satellite constellations, or across multiple signal frequencies, will have more information with which to calculate a more accurate position. But nothing impacts your performance quite like your antenna placement; antennas with a clear view of the sky can 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: https://novatel.com/support/knowledge...

You can also reduce errors through Corrections Services networks. Depending on your location and desired accuracy, you may choose one or more corrections services that provide additional information to your positioning solution. In this episode, we review three service types: satellite-based augmentation systems (SBAS), real-time kinematic (RTK), and precise point positioning (PPP).

Countries around the world have their own SBAS networks that are managed regionally. Using the network of base stations at known coordinates, the master station computes corrections between your solution and the base stations. This technique reduces atmospheric, satellite timing, and orbital errors. Corrections are freely available to all users in the covered region, providing nearly immediate meter-level accuracy.

RTK is another regional solution that relies on base stations. Using the carrier phase calculation explained in episode three, the base station resolves positioning ambiguities between its known location and your solution’s unknown location. This process outputs centimeter-level accuracy, but it is limited to a 20-30 kilometer area (as opposed to the SBAS solution’s country-wide area).

PPP correction services use an expansive global network of base stations to provide corrections, model clock and orbit errors, and resolve pseudorange and carrier phase biases. These corrections are downloaded by your positioning solution through the internet. While PPP enables accuracy in the decimeter range, it does require time for the receiver to properly compute any remaining errors. This time is called “convergence time.” But advances in technology are improving this performance with some services now providing centimeter level performance in under a few minutes.

When choosing a correction service to use, consider what services are available near you, what are your hardware and infrastructure requirements, and what kind of reliability and accuracy do you need.

Each correction type has benefits and limitations, and their use ultimately depends on your application requirements. Some users choose to use multiple correction sources to provide extra coverage, redundancy and reliability. Regardless of which service you choose, the additional information supplied by corrections all improve the GNSS position calculated by your receiver.

That concludes our section on reducing errors through GNSS equipment and correction services. Our next episode will describe how to use additional sensors like inertial navigation systems to enhance your position even further. If you’re ready to start learning these GNSS concepts, you can download our book An Introduction to GNSS: https://novatel.com/support/knowledge...