ESA’s efforts for more consistent geodetic products

<p>The importance of an accurate global geodetic reference frame and associated Earth orientation parameters is undisputed and has been recognised by the UN resolution 69/266. Given the importance of global geodetic references,  ESA is actively contributing to the IAG services: IGS, ILRS, IDS and the contribution to the IVS is in preparation.</p><p>ESA’s activities can be divided into four main areas: the operation of Ground Infrastructure (ESTRACK, EGON, …), the establishment and improvement of inter-technique ties, the operation of a scientific data archive (GSSC) and the generation of geodetic products and services.</p><p>This presentation will focus on the activities performed by the Navigation Support Office. The Navigation Support Office at ESA/ESOC is responsible for providing the Geodetic Reference Frame for all ESA missions and is also the Consortium Coordinator of the Galileo Geodetic Service Provider (GGSP) that generates the Galileo Geodetic Reference Frame (GTRF). Within its responsibilities, the Navigation Support Office is continuously working on improving the consistency of its geodetic products. The possibility to perform a Combination On the Observation Level (CoOL) for all geodetic observations is an excellent tool to identify inconsistencies. Over the recent years, significant improvements have been implemented in the data processing in order to enhance the consistency of the delivered products. As the status of the inter-technique ties remains a limiting factor in this context, ESA is currently investigating the possibility of using space ties, e.g. combining GNSS, SLR, DORIS and VLBI in space.</p><p>This presentation will give an overview of the geodetic products and services generated by ESA’s Navigation Support Office and outline the associated processing setup. In particular, it will report on the analysis performed to improve the consistency of the results provided by the different observation techniques and outline the recent improvements and ongoing activities.</p>

Sistemas Geodésicos de Referência: Rumo ao GGRS/GGRF

O estabelecimento de Sistemas Geodésicos de Referência globais integrando características geométricas e físicas é um dos desafios atuais da Geodésia, principalmente devido às demandas de diversas áreas do conhecimento de que as informações relacionadas aos Sistemas de Observação da Terra (EOS – Earth Observation Systems), sejam integradas em Redes Geodésicas de Referência (RGRs) com uma acurácia de 10-9 ou melhor. O surgimento das técnicas de posicionamento espacial trouxe melhora significativa na qualidade posicional e possibilitou a substituição das RGRs clássicas por redes modernas com características globais. Hoje, a questão das coordenadas de caráter geométrico, está bem resolvida com o ITRS/ITRF (International Terrestrial Reference System/International Terrestrial Reference Frame). Todavia, aspectos associados a diversos processos físicos, tais como os reflexos das redistribuições de massa, não são atendidos por referenciais puramente geométricos. A aprovação da resolução para o GGRS/GGRF (Global Geodetic Reference System/Global Geodetic Reference Frame) surge com a visão da integração entre o referencial terrestre, o celeste, um referencial com características físicas para as altitudes e a nova rede global de gravidade absoluta. Esforços têm sido feitos para definição e realização deste referencial global para as altitudes. É uma tarefa complexa em vista das características clássicas dos referenciais verticais, heterogeneidade em termos de qualidade e distribuição espacial de dados necessários, principalmente os relacionados ao campo de gravidade da Terra. Apresentam-se como grandes desafios para o futuro a necessidade de estabelecimento de procedimentos padrão para a integração ao referencial altimétrico global e a precisão necessária para o estabelecimento dos EOS.

Evaluating the Stability and Adequacy of NIGNET for the Definition of Nigerian Geodetic Reference Frame

A set of Continuously Operating Reference Stations (CORS) distributed all over Nigeria constitutes the Nigerian GNSS Reference Network referred to as NIGNET. Global Navigation Satellite System (GNSS) is a system tha uses satellites for autonomous position determination, and is a critical component of the modern-day geodetic infrastructure and services. Using CORS provide geodetic controls of comparable accuracy and a better alternative to the classical geodetic network. As the NIGNET infrastructure is utilised for different geodetic applications, it has become necessary to evaluate the suitability of the network data for the definition of a geodetic reference frame (GRF). This study utilised the technique of Precise Point Positioning (PPP) in position estimation, and time series analysis for temporal monitoring of the network. The sufficiency and adequacy of the NIGNET data archive was also evaluated against that of an International GNSS Service (IGS) Station. The temporal stability of the station coordinates measured in terms of standard deviations varied between 10 mm and 22 mm. This analysis suggests a relative stability required for Tiers 1 and 2 CORS in line with the IGS standards. Based on this reported stability, it is concluded that NIGNET is fit for purpose in defining the Nigerian Geodetic Reference Frame. However, despite the good data quality observed, the adequacy of the network has been compromised by infrastructural failures and lack of continuity in data transmission. Accordingly, it is recommended that both practical and policy measures required to ensure the realisation of the goal of the network should be implemented. Keywords: Geodetic reference frame, NIGNET, CORS, precise point positioning, temporal stability and adequacy.

Continuously operating reference stations in Russia: current state and future enhancements

<p>     At the present time the Russian  state geodetic reference frame of the new generation consists of the three hierarchical levels that include: 1. fundamental astronomical-geodetic reference frame ; 2. high-precision geodetic reference frame; 3. satellite-based geodetic reference frame of the first category.  The spatial coordinates of the networks of these three levels are determined by satellite methods.   However, only the points of the fundamental astronomical-geodetic reference frame are continuously operating reference stations.  Many surveying engineers, geodesists, map-ping specialists, as well as scientists from different backgrounds, are using RINEX files every day freely downloading them from the site //rgs.centre.ru</p><p>    At the same time, private networks of Continuously operating reference stations are developing rapidly in Russia. These networks are owned by various corporations, both private and public, as well as stations owned by private individuals.  Now,  a center is being created, the main task of which is to unite all Continuously operating reference stations located on the territory of Russia into a unified network.</p><p>    This paper addresses the current state of the Continuously operating reference stations network  in Russia and plans for enhancing it within the next few years.</p><p>Key words: Russian continuously operating reference stations network</p>

Developing a highly-available GNSS reference station network

<p>Having modern and well-maintained geodetic infrastructure is critical for the development of an accurate and reliable Global Geodetic Reference Frame (GGRF). Geoscience Australia (GA) contributes to the development of the GGRF through a network of Global Navigation Satellite System (GNSS) reference stations positioned in key locations across Australia, Antarctica and the Pacific. Data from these reference stations contribute to the realisation of the GGRF, the development and maintenance of the Asia-Pacific Reference frame and the monitoring of deformation across the Australian continent. We are also seeing a rapid increase in the use of this data for location-based positioning applications, such as civil engineering, transport, agriculture and community safety. These applications bring with them a new suite of challenges for geodetic infrastructure operators, such as reduced data latency, denser networks and accessing the latest signals in the most modern formats. Through the Positioning Australia program, GA is addressing these challenges by developing a modern highly-available GNSS reference station design that will be deployed at over 200 sites across the region. This paper discusses the concept of highly-available infrastructure and presents a GNSS reference station design that is openly available for use by the global geodetic community.</p>

GOM20: A Stable Geodetic Reference Frame for Subsidence, Faulting, and Sea-Level Rise Studies along the Coast of the Gulf of Mexico

We have established a stable regional geodetic reference frame using long-history (13.5 years on average) observations from 55 continuously operated Global Navigation Satellite System (GNSS) stations adjacent to the Gulf of Mexico (GOM). The regional reference frame, designated as GOM20, is aligned in origin and scale with the International GNSS Reference Frame 2014 (IGS14). The primary product from this study is the seven-parameters for transforming the Earth-Centered-Earth-Fixed (ECEF) Cartesian coordinates from IGS14 to GOM20. The frame stability of GOM20 is approximately 0.3 mm/year in the horizontal directions and 0.5 mm/year in the vertical direction. The regional reference frame can be confidently used for the time window from the 1990s to 2030 without causing positional errors larger than the accuracy of 24-h static GNSS measurements. Applications of GOM20 in delineating rapid urban subsidence, coastal subsidence and faulting, and sea-level rise are demonstrated in this article. According to this study, subsidence faster than 2 cm/year is ongoing in several major cities in central Mexico, with the most rapid subsidence reaching to 27 cm/year in Mexico City; a large portion of the Texas and Louisiana coasts are subsiding at 3 to 6.5 mm/year; the average sea-level-rise rate (with respect to GOM20) along the Gulf coast is 2.6 mm/year with a 95% confidence interval of ±1 mm/year during the past five decades. GOM20 provides a consistent platform to integrate ground deformational observations from different remote sensing techniques (e.g., GPS, InSAR, LiDAR, UAV-Photogrammetry) and ground surveys (e.g., tide gauge, leveling surveying) into a unified geodetic reference frame and enables multidisciplinary and cross-disciplinary research.

Semi-kinematic geodetic reference frame based on the ITRF2014 for Malaysia

Malaysia is located at the stable part of the tec-tonic Sundaland platelet in SE Asia. The platelet is surrounded in almost every direction by tectonically active convergent boundaries, at which the Philippine Sea, the Australian and the Indian Plates are subducting respectively from the East, South and West.The current Malaysia geodetic reference frame called MGRF2000 is a static reference frame and hence did not incorporate the effects of plate motion and the ensuing deformation from (megath-rust) earthquakes. To prevent degradation of Continuously Operating Reference Station (CORS) coordinates, a new time-dependent national reference frame was developed. Taking advantage of the availability of the GNSS data of the CORS network in Malaysia, notably the Malaysia Active GPS System (MASS) and Malaysia Real-Time Kinematic GNSS Network (MyRTKnet), a more accurate and robust Malaysian geodetic reference frame was determined, fully aligned and compatible with ITRF2014. The cumulative solution obtained from stacking Malaysian CORS position time series formed the basis of the new MGRF2020 realization. It consists of 100+ station positions at epoch 2020.0, station velocities and Post-Seismic Deformation (PSD) parametric models for stations subjected to major earthquakes. The (1999-2018) position time series exhibit Weighted Mean Root Square (WRMS) values of 3.0, 3.2 and 7.6 mm in respectively the East, North and Vertical components. A new semi-kinematic geodetic datum (GDM2020) for Malaysia, useable for GIS, mapping and cadastre applications is proposed to replace the existing static datum (GDM2000). A transformation suite to convert the spatial databases from GDM2000 to GDM2020 was also developed.