## How is ITRF defined?

The ITRF comprises concrete points (markers) attached to the solid Earth crust with precisely determined coordinates (mean 3D positions of the stations and their motions).

## What is the difference between ITRS and ITRF?

An International Terrestrial Reference Frame (ITRF) is a realization of the ITRS. Its origin is at the center of mass of the whole earth including the oceans and atmosphere.

**Which ellipsoid is used in ITRF system?**

Geodetic Reference System 1980 (GRS80) ellipsoid

IERS recommends to use the Geodetic Reference System 1980 (GRS80) ellipsoid as its reference ellipsoid with the geometric center of the ellipsoid coincident with the center of mass of the Earth and the origin of the coordinate system.

**What is WGS84 ellipsoid?**

WGS84 is standard for GPS It’s made up of a reference ellipsoid, a standard coordinate system, altitude data, and a geoid. Similar to the North American Datum of 1983 (NAD83), it uses the Earth’s center mass as the coordinate origin. Geodesists believe the error is less than 2 centimeters which is better than NAD83.

### What is the difference between WGS84 and Itrf?

The main difference between ITRF and WGS84 reference frameworks is the choice of fixed stations used in their adjustments. Not surprisingly, the difference between WGS84 and ITRF 2000 is now very small, generally less than 10 millimetres.

### What is terrestrial ellipsoid?

An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth’s form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations.

**What is Itrf datum?**

One of the main objectives of the International Terrestrial Reference Frame (ITRF) is to provide a standard global reference frame having the most attainable accuracy of its datum definition in terms of its origin, scale and the time evolution of its orientation.

**Which parameters are used to define an ellipsoid?**

Ellipsoid parameters The shape of an ellipsoid of revolution is determined by the shape parameters of that ellipse. The semi-major axis of the ellipse, a, becomes the equatorial radius of the ellipsoid: the semi-minor axis of the ellipse, b, becomes the distance from the centre to either pole.