Explore the vast range of titles available.

All papers published in this volume have been reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing Publishing.• Type of peer review: Single Anonymous• Conference submission management system: Morressier• Number of submissions received: 32• Number of submissions sent for review: 32• Number of submissions accepted: 29• Acceptance Rate (Submissions Accepted / Submissions Received × 100): 90.6• Average number of reviews per paper: 1• Total number of reviewers involved: 23• Contact person for queries:Name: Assoc. Prof. Tony VenelinovEmail: tvenelinov_fhe@uacg.bgAffiliation: University of Architecture, Civil engineering and Geodesy, Sofia, Bulgaria

All papers published in this volume have been reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing Publishing.• Type of peer review: Single Anonymous• Conference submission management system: Morressier• Number of submissions received: 61• Number of submissions sent for review: 61• Number of submissions accepted: 49• Acceptance Rate (Submissions Accepted / Submissions Received × 100): 80.3• Average number of reviews per paper: 1• Total number of reviewers involved: 11• Contact person for queries:Name: Dr. Filsa BioresitaEmail: filsa_b@geodesy.its.ac.idAffiliation: Department of Geomatics Engineering, Institut Teknologi Sepuluh Nopember, Kampus ITS, Keputih, Sukolilo, Surabaya, 60111, Indonesia

Space and time on earth are regulated by the Prime Meridian, 0ہ, which is, by convention, based at the Royal Observatory, Greenwich. But the meridian's location in southeast London is not a simple legacy of Britain's imperial past. Before the nineteenth century, more than twenty-five different prime meridians were in use around the world, including Paris, Beijing, Greenwich, Washington, and the location traditional in Europe since Ptolemy, the Canary Islands. Charles Withers explains how the choice of Greenwich to mark 0ہ longitude solved complex problems of global measurement that had engaged geographers, astronomers, and mariners since ancient times. Withers guides readers through the navigation and astronomy associated with diverse meridians and explains the problems that these cartographic lines both solved and created. He shows that as science and commerce became more global and as railway and telegraph networks tied the world closer together, the multiplicity of prime meridians led to ever greater confusion in the coordination of time and the geographical division of space. After a series of international scientific meetings, notably the 1884 International Meridian Conference in Washington, DC, Greenwich emerged as the most pragmatic choice for a global prime meridian, though not unanimously or without acrimony. Even after 1884, other prime meridians remained in use for decades. As Zero Degrees shows, geographies of the prime meridian are a testament to the power of maps, the challenges of accurate measurement on a global scale, and the role of scientific authority in creating the modern world.-- Provided by publisher.

The aim of this contribution is twofold. First, we show that when two (or more) different quantum groups share the same noncommutative spacetime, such an ‘ambiguity’ can be resolved by considering together their corresponding noncommutative spaces of geodesics. In any case, the latter play a mathematical/physical role by themselves and, in some cases, they can be interpreted as deformed phase spaces. Second, we explicitly show that noncommutative spacetimes can be reproduced from ‘extended’ noncommutative spaces of geodesics which are those enlarged by the time translation generator. These general ideas are described in detail for the κ -Poincaré and κ -Galilei algebras.

\"A stunning geographical exploration of our world through 50 unique maps. Modern satellite and geographical technology has enabled the world to be researched in new and incredible detail. From measuring species diversity to monitoring land shifts, our physical and sociological world is mapped like never before. Includes 50 specially commissioned maps that examine our world in a beautifully visual and fascinating way. Alastair Bonnett accompanies each map with a vivid essay that provides detailed insight into how the planet has changed and what it may look like in the future. From examining new deserts and charting airspace, to revealing emerging lands and measuring each continent's natural treasures, each map showcases an important part of our world's history, sociology and of course, geography\"-- Provided by publisher.

P228

The International Laser Ranging Service (ILRS) was established by the International Association of Geodesy (IAG) in 1998 to support programs in geodesy, geophysics, fundamental constants and lunar research, and to provide the International Earth Rotation Service with data products that are essential to the maintenance and improvement in the International Terrestrial Reference Frame (ITRF), the basis for metric measurements of changes in the Earth and Earth–Moon system. Other scientific products derived from laser ranging include precise geocentric positions and motions of ground stations, satellite orbits, components of Earth’s gravity field and their temporal variations, Earth Orientation Parameters, precise lunar ephemerides and information about the internal structure of the Moon. Laser ranging systems are already measuring the one-way distance to remote optical receivers in space and are performing very accurate time transfer between remote sites in the Earth and in Space. The ILRS works closely with the IAG’s Global Geodetic Observing System. The ILRS develops (1) the standards and specifications necessary for product consistency, and (2) the priorities and tracking strategies required to maximize network efficiency. The service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with (1) new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity, and (2) science programs to optimize scientific data yield. Since its inception, the ILRS has grown to include forty laser ranging stations distributed around the world. The ILRS stations track more than ninety satellites from low Earth orbit (LEO) to the geosynchronous orbit altitude as well as retroreflector arrays on the surface of the Moon. Applications have been expanded to include time transfer, asynchronous ranging for targets at extended ranges, free space quantum telecommunications, and the tracking of space debris. Laser ranging technology is moving to lower energy, higher repetition rates (kHz), single-photon-sensitive detectors, shorter pulse widths, shorter normal point intervals for faster data acquisition, and increased pass interleaving, automated to autonomous operation with remote access, and embedded software for real-time updates and decision making. An example of pass interleaving is presented for the Yarragadee station (see Fig. 4); tracking of LEO satellites is often accommodated during break in LEO and GNSS passes. New satellites arrays provide more compact targets and work continues on the development of lighter less expensive arrays for satellites and the moon. The service now provides operational ITRF products including daily/weekly station positions and daily resolution Earth orientation products; the flow of weekly combination of satellite orbit files for LAGEOS/Etalon-1 and -2 has recently been established. New products are under testing through a pilot project on systematic error monitoring currently underway. The article will give an overview of activities underway within the service, paths forward presently envisioned, and current issues and challenges.

The primary objective of the 1-cm geoid experiment in Colorado (USA) is to compare the numerous geoid computation methods used by different groups around the world. This is intended to lay the foundations for tuning computation methods to achieve the sought after 1-cm accuracy, and also evaluate how this accuracy may be robustly assessed. In this experiment, (quasi)geoid models were computed using the same input data provided by the US National Geodetic Survey (NGS), but using different methodologies. The rugged mountainous study area (730 km × 560 km) in Colorado was chosen so as to accentuate any differences between the methodologies, and to take advantage of newly collected GPS/leveling data of the Geoid Slope Validation Survey 2017 (GSVS17) which are now available to be used as an accurate and independent test dataset. Fourteen groups from fourteen countries submitted a gravimetric geoid and a quasigeoid model in a 1′ × 1′ grid for the study area, as well as geoid heights, height anomalies, and geopotential values at the 223 GSVS17 marks. This paper concentrates on the quasigeoid model comparison and evaluation, while the geopotential value investigations are presented as a separate paper (Sánchez et al. in J Geodesy 95(3):1. https://doi.org/10.1007/s00190-021-01481-0 , 2021). Three comparisons are performed: the area comparison to show the model precision, the comparison with the GSVS17 data to estimate the relative accuracy of the models, and the differential quasigeoid (slope) comparison with GSVS17 to assess the relative accuracy of the height anomalies at different baseline lengths. The results show that the precision of the 1′ × 1′ models over the complete area is about 2 cm, while the accuracy estimates along the GSVS17 profile range from 1.2 cm to 3.4 cm. Considering that the GSVS17 does not pass the roughest terrain, we estimate that the quasigeoid can be computed with an accuracy of ~ 2 cm in Colorado. The slope comparisons show that RMS values of the differences vary from 2 to 8 cm in all baseline lengths. Although the 2-cm precision and 2-cm relative accuracy have been estimated in such a rugged region, the experiment has not reached the 1-cm accuracy goal. At this point, the different accuracy estimates are not a proof of the superiority of one methodology over another because the model precision and accuracy of the GSVS17-derived height anomalies are at a similar level. It appears that the differences are not primarily caused by differences in theory, but that they originate mostly from numerical computations and/or data processing techniques. Consequently, recommendations to improve the model precision toward the 1-cm accuracy are also given in this paper.