Precise point positioning (PPP) using global navigation satellite systems (GNSS) enables accurate positioning worldwide. Recent advances, including improved error source modelling and the modernization of GNSS constellations, have reduced the time required to achieve cm-level accuracies from hours to seconds, creating new possibilities for several applications. To address remaining technical issues in this area, the Remote Sensing journal has created a special issue dedicated to PPP.
Only recently, fast convergence of PPP-RTK solutions depended on the proximity of users to a regional network of ground stations. Obtaining quasi-instantaneous cm-level accuracies worldwide seemed like a utopic goal. But two weeks ago, Hexagon's Autonomy and Positioning division announced “RTK From the Sky”, a technology that enables such positioning feat. In this blog post, I offer insights into what it takes to achieve rapid PPP convergence at a global level.
I have been talking about it for years now, but it is finally coming: in October 2020, CSRS-PPP will offer precise point positioning with ambiguity resolution (PPP-AR) solutions for data collected on or after 1 January 2018.
Since August 2018, the CSRS-PPP service is supporting RINEX version 3. While this feature was necessary to keep up with modernization efforts within the GNSS community, it led to further challenges that were not an issue with RINEX 2. This blog post explains some of the issues encountered and describes how CSRS-PPP v2.31, released this week, helps in mitigating them.
Algorithms for precise point positioning with ambiguity resolution (PPP-AR) were developed over a decade ago. Since then, techniques have matured and most analysis centres (ACs) of the International GNSS Service (IGS) now produce products enabling PPP-AR. The IGS PPP-AR working group, created during the 2018 IGS workshop in Wuhan, investigated the interoperability of such products and recently published a paper on this topic in the Journal of Geodesy.
To obtain the highest accuracy from precise point positioning (PPP) solutions, consistency between network and user algorithms must be ensured. An error source prone to mismodelling is satellite attitude, especially during eclipse periods. This blog post explains how to use data from an attitude exchange format being tested within the IGS.
The annual ION GNSS+ meeting was held in Miami, Florida, from September 16 - 20, 2019. I was surprised, and initially disappointed, that there was no session dedicated to precise point positioning (PPP) this year. However, it quickly became clear that PPP-related research is still going strong: it has simply evolved to focus on low-cost GNSS devices, smartphones and integrity.
While writing my ION GNSS+ 2019 paper, I realized I should use some sort of checklist to ensure that my work meets basic quality requirements. I may sound like I have been brainwashed by ISO certification but, especially as a reviewer, I wish everybody would follow this checklist to the letter. This is still work in progress, so if you can contribute further advice, please feel free to leave a comment!
Will PPP ever replace RTK? Over the past decade, we have seen the convergence of PPP and RTK towards “PPP-RTK,” where satellite orbit/clock/bias corrections are augmented by local atmospheric corrections to enable instantaneous convergence to cm-level accuracies. But how close are we to instantaneous cm-level PPP-AR, without local augmentation?
After an 8-month interruption, I am thrilled to announce that the BlackDotGNSS blog is back! While management was supportive of this initiative, issues were raised by the ethics committee regarding information sharing and it was recommended to abort this activity. I recently had the opportunity to have a face-to-face discussion with members of this committee, and I learned that blogging is allowed under certain conditions.