************************************************************************ IERS Message No. 429 April 07, 2021 ************************************************************************ IAG 2021, Session 1.3 on multi-technique combinations Dear Colleagues, We would like to draw your attention to Session 1.3 "Terrestrial and space geodetic ties for multi-technique combinations" of the upcoming Scientific Assembly of the International Association of Geodesy, taking place as virtual meeting between June 28 - July 02, 2021. Please consider to submit an abstract to this session. See http://www.iag2021.com/en/web/index/1646_140108 for this and other sessions of the Commission 1 Symposium. Abstract submission deadline is 30th April, 2021 (http://www.iag2021.com/en/web/index/1646_802946). We are looking forward to your contributions. With apologies for cross-postings. Best regards, Urs Hugentobler, Krzysztof Sosnica, Weiping Jiang Session 1.3: Terrestrial and space geodetic ties for multi-technique combinations Consistent combination of space geodetic techniques is a necessity for a full exploitation of the relative strength of the techniques for the generation of accurate and long-term stable geodetic products. Essential for this task are precise ties between the different techniques, co-located on ground and in space. This session aims at a review of the state-of-the art and outlook to future prospects as well as assessment of the impact on geodetic products of precision sight surveys, monitoring of temporal variations of tie vectors, identification of technique-specific biases, space geodetic combination methodologies, but also of using additional and novel tie information such as intra- and inter-technique tropospheric ties or ties realized through common clock parameters at geodetic observatories, as well as exploitation of already existing space ties such as SLR observations of GNSS satellites, experiments of observing GNSS satellites with VLBI, and simulations of the impact and benefit of future space co-location missions. The following topics are of specific importance: * Identification of technique-specific biases. * Temporal variations of tie vectors at co-located stations. * Intra- and inter-technique ties based on tropospheric parameters and common clock parameters. * Space-based ties using GNSS-satellite tracking via SLR or VLBI measurements. Keywords: Terrestrial/space geodetic ties, terrestrial reference frames, multi-technique combination, local tie vectors, co-located techniques, tropospheric parameters, SLR-to-GPS tracking. ************************************************************************ IERS Messages are edited and distributed by the IERS Central Bureau. If not stated otherwise, the IERS is only the distributor of the message and is not responsible for its content. To submit texts for distribution, please write to . To subscribe or unsubscribe, please create an IERS account or modify it: https://www.iers.org/Login/Login/EN/login_node.html or write to . Archives: http://www.iers.org/Messages ************************************************************************