ITRF2020 (International Terrestrial Reference Frame 2020)

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Introduction

ITRF2020 (International Terrestrial Reference Frame 2020) is the latest earth reference frame officially released by the International Earth Rotation and Reference Systems Service (IERS) in 2022. The ITRF series is designed to define positions and motions on the earth with high precision. ITRF2020 is the successor to the traditional ITRF2014, and its updates are designed to improve the accuracy of observation techniques and respond to crustal movements. The reference frame is constructed from data from four observation techniques: VLBI (Very Long Baseline Interferometry), SLR (Satellite Laser Ranging), GNSS (Global Navigation Satellite System) and DORIS (Doppler Orbiting Integrated with Radio Positioning).

Coordinate System Composition

Coordinate data: Cartesian coordinate system format based on three-dimensional position (X, Y, Z), including annual changes (velocity components) of each observation station.
Velocity model: Provides velocity vectors that take into account crustal deformation (linear motion + nonlinear components) at each observation station.
Time label: Time series data based on the observation period (reference time is 2020.0).
Software compatibility: Compatible with GNSS analysis software such as GIPSY, Bernese and RTKLIB.

Pros

More accurate coordinate reference: Compared with the previous version ITRF2014, its accuracy has been improved, especially in the southern hemisphere and some plate boundary areas.
Nonlinear crustal motion modeling: Explicitly consider nonlinear motion associated with large earthquakes and long-term crustal motion, suppressing the decrease in position accuracy over time.
**Compatible with the latest observation technology: **It can reflect high-precision geodetic observation data as of 2020 and has high reliability in multi-GNSS environments.
**Global compatibility: **Global reference stations can adopt unified standards, which is conducive to international data sharing and the integration of measurement standards.

Cons

Complexity in handling nonlinear components: Handling nonlinear crustal motion requires more complex calculations than traditional linear approximation models, and requires certain expertise for software and data analysis.
Compatibility issues with older systems: Differences may occur when using ITRF2014 or ITRF2008 for coordinate conversion, and additional work may be required to ensure consistency with databases built on older versions of the standard.
Infrastructure requirements to take advantage of high precision: If the observation equipment and analysis environment are older, the accuracy advantages of ITRF2020 may not be fully utilized.

Application Scenario

ITRF2020 has a wide range of applications, including surveying and mapping, GNSS positioning, crustal movement analysis, geophysics, sea level change monitoring, spacecraft trajectory calculation, and national reference coordinate system updates. It plays an important role in improving the accuracy of GNSS observation networks, accurately grasping the laws of crustal movement for disaster prediction and reconstruction planning, and unifying location information between multiple countries and regions.

Example

Sites used for estimating conversion parameters between ITRF2020 and ITRF2014.

Distribution of ITRF sites [Source: Altamimi et al.].