science

International Terrestrial Reference System and Frame

International Terrestrial Reference System and Frame is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand International Terrestrial Reference System and Frame rather than just read about it. In short: The International Terrestrial Reference System (ITRS) describes procedures for creating reference frames suitable for use with measurements on or near the Earth's surface. This is done in much the same way that a physical standard might be described as a set of procedures for creating a realization of that standard.

Key takeaways

International Terrestrial Reference System and Frame belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect International Terrestrial Reference System and Frame to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of International Terrestrial Reference System and Frame from memory before moving on to harder problems.

Reference excerpt

The International Terrestrial Reference System (ITRS) describes procedures for creating reference frames suitable for use with measurements on or near the Earth's surface. This is done in much the same way that a physical standard might be described as a set of procedures for creating a realization of that standard. The ITRS defines a geocentric system of coordinates using the SI system of measurement. 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. New ITRF solutions are produced every few years, using the latest mathematical and surveying techniques to attempt to realize the ITRS as precisely as possible. Due to experimental error, any given ITRF will differ very slightly from any other realization of the ITRF. The difference between the latest as of 2006 WGS 84 (frame realisation G1150) and the latest ITRF2000 is only a few centimeters and RMS difference of one centimeter per component. ITRFs are Earth-centered, Earth-fixed (ECEF) reference frames. The ITRS and ITRF solutions are maintained by the International Earth Rotation and Reference Systems Service (IERS). Practical navigation systems are in general referenced to a specific ITRF solution, or to their own coordinate systems which are then referenced to an ITRF solution. For example, the Galileo Terrestrial Reference Frame (GTRF) is used for the Galileo navigation system; currently defined as ITRF2005 by the European Space Agency.

Versions The ITRF realizations developed from the ITRS since 1991 include the following versions:

Users GNSS systems:

Galileo Terrestrial Reference Frame (GTRF), ITRF2005; own implementation using IGS sites. GPS just uses WGS 84, ITRF2020 since January 2024 (but used many versions of WGS 84 before), a little modified with International GNSS Service (IGS) implementation, IGS20. BeiDou Coordinate System, China Terrestrial Reference Frame (CTRF) 2000 = ITRF97 at epoch 2000.0; own implementation. GLONASS PZ-90.11 is nominally its own system, but is quite close to ITRF and uses many of the same techniques. National systems:

United States: WGS 84 (see above); domestic use is mainly based on NAD 83 instead. China: CTRF 2000 per above. The GPS reference epoch was moved from 2000.0 to 2001.0 in G1150 due to the magnitude 7.9 Denali Fault earthquake in Alaska in November 2002. Still in 2022 ITRF2020 was released, yet GPS was only using G2139 in its antennas, which was aligned to ITRF2014 (IGb14) (though at epoch 2016.0, not reference epoch 2010.0). On 7 January 2024 move to IGS20 happened, so WGS 84 is now aligned with ITRF2020, including PSD (post-seismic deformation), also called G2296. On the other hand GLONASS is using PZ-90.11, which is close to ITRF2008 at epoch 2011.0 and is using 2010.0 epoch (that means when you use reference transformation to PZ-90.11 you will get January 2010 date).

See also Earth-centered, Earth-fixed coordinate system Earth orientation parameters Geodetic datum International Celestial Reference System and its realizations Terrestrial reference frame World Geodetic System

References

External links Forward and backward transformations using 14 parameters Helmert Convertor between ITRF realisations with changing the epoch and tectonics, tectonics for it What is ITRF? Terrestrial reference systems and frames (PDF; chapter 4 of IERS Conventions 2010)

Illustrations

Worked examples

Example 1 — a first encounter with International Terrestrial Reference System and Frame

Start with the simplest possible case. Write down what International Terrestrial Reference System and Frame claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to International Terrestrial Reference System and Frame before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about International Terrestrial Reference System and Frame ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of International Terrestrial Reference System and Frame

In research: International Terrestrial Reference System and Frame appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses International Terrestrial Reference System and Frame in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: International Terrestrial Reference System and Frame is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geodetic datums, so understanding it makes those chapters shorter.
In everyday life: Look for International Terrestrial Reference System and Frame outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study International Terrestrial Reference System and Frame in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what International Terrestrial Reference System and Frame means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain International Terrestrial Reference System and Frame out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is International Terrestrial Reference System and Frame in simple terms?

Why does International Terrestrial Reference System and Frame matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study International Terrestrial Reference System and Frame?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on International Terrestrial Reference System and Frame.