Simon Lutz

The CODE MGEX orbit and clock solution

The Center for Orbit Determination in Europe (CODE) is contributing as a global analysis center to the International GNSS Service (IGS) since many years. The processing of GPS and GLONASS data is well established in CODE’s ultra-rapid, rapid, and final product lines. With the introduction of new signals for the established and new GNSS, new challenges and opportunities are arising for the GNSS data management and processing. The IGS started the Multi-GNSS-EXperiment (MGEX) in 2012 in order to gain first experience with the new data formats and to develop new strategies for making optimal use of these additional measurements. CODE has started to contribute to IGS MGEX with a consistent, rigorously combined triple-system orbit solution (GPS, GLONASS, and Galileo). SLR residuals for the computed Galileo satellite orbits are of the order of 10 cm. Furthermore CODE established a GPS and Galileo clock solution. A quality assessment shows that these experimental orbit and clock products allow even a Galileo-only precise point positioning (PPP) with accuracies on the decimeter- (static PPP) to meter-level (kinematic PPP) for selected stations.

CODE's new ultra-rapid orbit and ERP products for the IGS

Abstract The International GNSS Service (IGS) issues four sets of so-called ultra-rapid products per day, which are based on the contributions of the IGS Analysis Centers. The traditional (“old”) ultra-rapid orbit and earth rotation parameters (ERP) solution of the Center for Orbit Determination in Europe (CODE) was based on the output of three consecutive 3-day long-arc rapid solutions. Information from the IERS Bulletin A was required to generate the predicted part of the old CODE ultra-rapid product. The current (“new”) product, activated in November 2013, is based on the output of exactly one multi-day solution. A priori information from the IERS Bulletin A is no longer required for generating and predicting the orbits and ERPs. This article discusses the transition from the old to the new CODE ultra-rapid orbit and ERP products and the associated improvement in reliability and performance. All solutions used in this article were generated with the development version of the Bernese GNSS Software. The package was slightly extended to meet the needs of the new CODE ultra-rapid generation.

Near Real-Time Coordinate Estimation from Double-Difference GNSS Data - A Case Study for the National Multi-Hazard Early Warning System in the Sultanate of Oman

Real-time and near real-time coordinate estimation become increasingly important in many applications like, e.g., environmental hazard monitoring. The typical approach is based on a Precise Point Positioning (PPP), which has the advantage that all stations can be processed independently and, therefore, the processing of monitoring networks with a large number of stations becomes efficient due to parallelization. However, a PPP requires external satellite clock corrections and the accuracy of the obtained coordinates strongly depends on the consistent usage of these clock corrections and on their quality. Since the processing time for real-time products is strictly limited, it is clear that, in general, the quality of such clock corrections is degraded w.r.t. post-processed products.The purpose of this article is to demonstrate that the classical double-difference network approach, where no accurate satellite clock corrections are needed, has a lot of potential also for near real-time applications, when a latency of a few minutes is acceptable. The presented results were obtained in the framework of the establishment of a National Multi-Hazard Early Warning System in the Sultanate of Oman.

CODE Analysis center: Technical Report 2015

Applications of the Global Navigation Satellite Systems (GNSS) to Earth Sciences are numerous. The International GNSS Service (IGS), a voluntary federation of government agencies, universities and research institutions, combines GNSS resources and expertise to provide the highest–quality GNSS data, products, and services in order to support high–precision applications for GNSS–related research and engineering activities. This IGS Technical Report 2015 includes contributions from the IGS Governing Board, the Central Bureau, Analysis Centers, Data Centers, station and network operators, working groups, pilot projects, and others highlighting status and important activities, changes and results that took place and were achieved during 2015.

Erratum to: Impact of the arc length on GNSS analysis results

6 Bundesamt für Kartographie und Geodäsie, Richard-Strauss-Allee 11, 60598 Frankfurt am Main, Germany day to day, orbit misclosures in the Earth-fixed system exclusively characterize the difference of the orbits at the day boundaries in one and the same reference frame. In the inertial system the pole misclosures (Eq. 1) affect the orbit misclosures, as well. Subsequently, we uniquely analyze the orbit misclosures in the inertial system.”

Near Real-Time Coordinate Estimation from Double-Difference GNSS Data

Real-time and near real-time coordinate estimation become increasingly important in many applications like, e.g., environmental hazard monitoring. The typical approach is based on a Precise Point Positioning (PPP), which has the advantage that all stations can be processed independently and, therefore, the processing of monitoring networks with a large number of stations becomes efficient due to parallelization. However, a PPP requires external satellite clock corrections and the accuracy of the obtained coordinates strongly depends on the consistent usage of these clock corrections and on their quality. Since the processing time for real-time products is strictly limited, it is clear that, in general, the quality of such clock corrections is degraded w.r.t. post-processed products.The purpose of this article is to demonstrate that the classical double-difference network approach, where no accurate satellite clock corrections are needed, has a lot of potential also for near real-time applications, when a latency of a few minutes is acceptable. The presented results were obtained in the framework of the establishment of a National Multi-Hazard Early Warning System in the Sultanate of Oman.

Monitoring of Antenna Changes at IGS Stations in Iceland

GNSS antenna changes are in particular critical for the long-term stability of the coordinate time series and the reference systems realized with these stations. Depending on the antenna types and the available antenna calibrations, discontinuities of up to several centimeters can be introduced. Therefore, a monitoring of the antenna changes is important to verify the continuity of the time series. In order to add Galileo tracking capability the GNSS equipment at the Icelandic IGS stations Reykjavik and Hoefn had to be replaced. Temporary GNSS sites were set up in the vicinity of both sites. These short baselines are analyzed with different observables. In addition, the temporary sites were included in the routine processing of the Center for Orbit Determination in Europe analysis center of the IGS. The equipment changes introduced discontinuities of up to 1.5 cm in the coordinates derived from the global solution. Depending on the analysis strategy and observables used, the results of the short baselines differ by up to 2.5 cm.