Review of Reference Frame Representations for a Deformable Earth
Our planet Earth is constantly deforming under the effects of geophysical processes that cause linear and nonlinear displacements of the geodetic stations upon which the International Terrestrial Reference Frame (ITRF) is established. The ITRF has traditi
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Abstract
Our planet Earth is constantly deforming under the effects of geophysical processes that cause linear and nonlinear displacements of the geodetic stations upon which the International Terrestrial Reference Frame (ITRF) is established. The ITRF has traditionally been defined as a secular (linear) frame in which station coordinates are described by piecewise linear functions of time. Nowadays, some particularly demanding applications however require more elaborate reference frame representations that can accommodate non-linear displacements of the reference stations. Two such types of reference frame representations are reviewed: the usual linear frame enhanced with additional parametric functions such as seasonal sine waves, and non-parametric time series of quasi-instantaneous reference frames. After introducing those two reference frame representations, we briefly review the systematic errors present in geodetic station position time series. We finally discuss the practical issues raised by the existence of these systematic errors for the implementation of both types of non-linear reference frames. Keywords
ITRF Nonlinear motions Reference frames Reference systems
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Introduction
Where am I and how to accurately navigate between places on Earth, oceans and in space? How to plan for territory and land management (construction, mining, civil engineering, national boundaries delimitation)? How to ensure that geospatial data are inter-operable within a country, a region and globally? How to locate areas and people at risk (natural disasters: earthquakes, tsunamis and flooding)? How to accurately determine orbits of artificial satellites? How to Z. Altamimi () · P. Rebischung · L. Métivier · K. Chanard Institut National de l’Information Géographique et Forestière (IGN), Université Paris Diderot, Paris, France e-mail: [email protected]; [email protected]; laurent. [email protected]; [email protected] X. Collilieux Ecole Nationale des Sciences Géographiques, Champs sur Marne, France e-mail: [email protected]
measure self-consistent sea level rise over several decades, through the usage of satellite altimetry data and tide gauges? How to accurately determine point positions on the Earth surface that is constantly deforming? In order to answer these crucial questions and to enable operational geodesy and Earth science applications, a unified terrestrial reference system and its materialization by an accurate terrestrial reference frame are needed. This is the purpose of the International Terrestrial Reference System (ITRS; see Chapter 4 in Petit and Luzum 2010) and of its materialization by the International Terrestrial Reference Frame (ITRF). The successive releases of the ITRF are provided in the form of reference regularized coordinates X .t/ for a set of geodetic stations, described by mathematical functions of time and obtained from the adjustment of data from the four contributing space geodetic techniques (VLBI, SLR, GNSS, DORIS). From ITRF91 (Altamimi et al. 1993; Boucher et
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