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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).

RD New (Rijksdriehoeksmeting New) is the national reference coordinate system of the Netherlands and the standard projection coordinate system for geographic information measurement and map production. The coordinate system is based on the Transverse Mercator Projection, with Amersfoort as the origin. It is widely known as EPSG code 28992. The system is designed to manage spatial data throughout the Netherlands with high accuracy and is currently widely used in public and private fields such as land management, urban planning, infrastructure design, and disaster response.

GPS Coordinate System, that is, the coordinate system used by the Global Positioning System, is usually based on the geographic coordinate system (EPSG:4326) WGS84 (World Geodetic System 1984). This is a universal reference system used to determine the longitude and latitude of any point on the earth. WGS84 is a geocentric coordinate system with the center of mass of the earth as the origin. It is widely used in navigation, surveying, mapping and geographic information systems (GIS).

Tokyo Datum (Tokyo 1918 | EPSG:4301) is a geodetic reference frame adopted by Japan in the early days. Its ellipsoidal parameters (such as the major semi-axis and inverse flattening) are set based on old surveying techniques, and the prime meridian passes through the original site of the Tokyo Observatory (not Greenwich). This coordinate system is mainly used for mapping and engineering surveying in Japan. After its establishment in 1918, it has long served the Japanese geographic information field. However, due to technical limitations, its accuracy and compatibility with international standards have gradually fallen behind.

GDA2020 is the latest geocentric coordinate reference frame launched by Australia in 2020. It is consistent with ITRF2014, providing the position and long-term velocity of the base station at the reference epoch, and includes the post-seismic deformation caused by large earthquakes and the annual and semi-annual parameter models. The accuracy of GDA2020 is improved compared to ITRF2014, and can meet the needs of high-precision geolocation and measurement.

Baidu Coordinate System (BD09), also known as Baidu Coordinate System, is a coordinate system developed by Baidu to meet the special needs of geographic information systems in mainland China. It is encrypted based on the WGS84 coordinate system (World Geodetic System 1984) to ensure accurate geographic positioning services within mainland China.

ETRS89 is the reference coordinate system for measurement and geographic information in Europe. Its goal is to establish a unified spatial reference frame across Europe.

Geographic Coordinate System (GCS) is a coordinate system based on a sphere or ellipsoid that is used to define locations on the surface of the Earth. It describes a location using two angular coordinates (usually latitude and longitude), and the third value can be an optional altitude value. GCS is widely used in fields such as geographic information systems (GIS), mapping, and navigation, and is the basis for expressing geographic data.

NAD83 (North American Datum 1983) is a geographic coordinate system (geographic reference system) widely used in North America, especially in the United States, Canada, and Mexico. It is a modernized, high-precision version of the previously used NAD27 (North American Datum 1927), developed with a focus on compatibility with GPS technology. Its EPSG code is 4269.

**SIRGAS 2000 **is a geocentric reference frame for Central and South America, which aims to define and implement a unified reference frame for Central and South America that is consistent with ITRF. Its ellipsoid adopts GRS 1980, with a major semi-axis of 6378137 meters, an oblateness of 298.257222101, the Greenwich meridian as the prime meridian, and the angle unit is degree. SIRGAS 2000 was established in 2000, consistent with the ITRF2000 framework, with a reference epoch of 2000.0. It is a regional encryption of ITRS in South America, achieved through a network of about 200 continuously operating stations (SIRGAS-CON) throughout Latin America and the Caribbean.