Tropospheric Products from High-Level GNSS Processing in Latin America

ARTÍCULO PUBLICADO EN REVISTA EXTERNA. The present geodetic reference frame in Latin America and the Caribbean is given by a network of about 400 continuously operating GNSS stations. These stations are routinely processed by ten Analysis Centres following the guidelines and standards set up by the International Earth Rotation and Reference Systems Service (IERS) and International GNSS Service (IGS). The Analysis Centres estimate daily and weekly station positions and station zenith tropospheric path delays (ZTD) with an hourly sampling rate. This contribution presents some attempts aiming at combining the individual ZTD estimations to generate consistent troposphere solutions over the entire region and to provide reliable time series of troposphere parameters, to be used as a reference. The study covers ZTD and IWV series for a time-span of 5 years (2014–2018). In addition to the combination of the individual solutions, some advances based on the precise point positioning technique using BNC software (BKG NTRIP Client) and Bernese GNSS Software V.5.2 are presented. Results are validated using the IGS ZTD products and radiosonde IWV data. The agreement was evaluated in terms of mean bias and rms of the ZTD differences w.r.t IGS products (mean bias 1.5 mm and mean rms 6.8 mm) and w.r.t ZTD from radiosonde data (mean bias 2 mm and mean rms 7.5 mm). IWV differences w.r.t radiosonde IWV data (mean bias 0.41 kg/m2 and mean rms 3.5 kg/m2).Sitio de la revista: https://link.springer.com/chapter/10.1007/1345_2020_12

Simulation case study of deformations and landslides using real-time GNSS precise point positioning technique

[EN] The precise point positioning (PPP) is a Global Navigation Satellite System (GNSS) computation technique that performs precise positioning using a single receiver. This is the main advantage over the traditional differential positioning for geodesy and geomatics which requires, at least, two receivers to get a precise position or a single receiver connected to a network of reference stations. The main goal of this work was to study the real-time PPP technique for deformation and landslides monitoring. A custom designed device was used for the simulation of landslides, and several test campaigns were performed at field. A control unit was designed based on open-source software and Python libraries implemented in this research. The conclusion of the study shows that realtime PPP allows solutions for deformation monitoring with mean offsets of 2 cm in north, east and up components, and standard deviations of 2 cm. It demonstrates the reliability of real-time PPP monitoring systems to detect deformations up to 5 cm of magnitude when the double constellation (GPSCGLONASS) was used. Finally, an improvement in the results with the recovery of fixed ambiguities in the PPP algorithms is outlined.Capilla Roma, R.; Berné Valero, JL.; Martín Furones, ÁE.; Rodrigo Alemany, R. (2016). Simulation case study of deformations and landslides using real-time GNSS precise point positioning technique. Geomatics, Natural Hazards and Risk. 7(6):1856-1873. doi:10.1080/19475705.2015.1137243S185618737

advanced gnss processing techniques working group 1

Over the last decade, near real-time analysis of GPS data has become a well-established atmospheric observing tool, primarily coordinated by the EIG EUMETNET GPS Water Vapour Programme (E-GVAP) in Europe. In the near future, four operational GNSS will be available for commercial and scientific applications with atmospheric science benefiting from new signals from up to 60 satellites observed at any one place and time, however, many challenges remain regarding their optimal combined utilization. Besides raw data streaming, recent availability of precise real-time orbit and clock corrections enable wide utilization of autonomous Precise Point Positioning (PPP), which is particularly efficient for high-rate, real-time and multi-GNSS analyses

Improved Constraints on Models of Glacial Isostatic Adjustment: A Review of the Contribution of Ground-based Geodetic Observations

The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA isuncertain due to insufficient constraints on our knowledge of past glacial changes and to large simplifications in the underlying Earth models. Consequently, we show differences between models that exceed several mm/year in terms of surface displacement for the two major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement offer the potential for new constraints to be made on GIA models, especially when they are used to improve structural features of the Earth’s interior as to allow for a more realistic reconstruction of the glaciation history. We present the distribution of presently available campaign and continuous geodetic measurements in Greenland and Antarctica and summarise surface velocities published to date, showing substantial disagreement between techniques and GIA models alike. We review the current state-of-the-art in ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise surface velocities. In particular, we focus on known areas of need in GPS observation level models and the terrestrial reference frame in order to advance geodetic observation precision/ accuracy toward 0.1 mm/year and therefore further constrain models of GIA and subsequent present-day ice mass change estimates