# Strategies and methods that Datums and Coordinate Systems use to account for movement of the earth's surface

Are there `datums` and `coordinate systems` that address the issue of shifting coordinates through time? If so, what are some of the strategies and methods that the `datums` and `coordinate systems` use to address the issue?

To provide some context:

Several Earth processes, plate tectonics and isostatic rebound, affect where a `(x, y, z)` location is (or perhaps better, is calculated to be) in a time step `t1` in comparison to a different time step `t2`. In some areas of the world, such as California, USA, this movement can be in the magnitude of centimeters per year. For some GIS analysis the shift in `(x, y, z)` locations could have a serious effect on the results, for example examining sediment flux that rely on comparing raster cells and/or coordinates across different time steps often spanning several years or decades.

• How are you defining your x,y,z ? Many coordinate systems are fixed with respect to what they apply to (see ga.gov.au/scientific-topics/positioning-navigation/geodesy/… for an Australian example, which is moving 7cm/year). – BradHards Oct 23 '15 at 6:22
• @BradHards Thank you for the link. This is the type of information I am looking for :-) This is more of an in general question and examples are welcome, I have edited the question to reflect that. It is difficult for me to answer your question. But in the example given of tracking sediment flux, I think the (x, y, z) can be defined in two ways (perhaps more) one which (x, y, z) tracks a location on the surface of a moving plate, the other (x, y, z) is a fixed location that depending on the time step could be a different location on the moving plate. – GeoSharp Oct 23 '15 at 6:52
• There are a couple of answers here which discuss NAD83(CSRS), Proj.4 and Natural Resources Canada's TRX tool, which transforms coordinates w/r/t tectonic and isostatic movement. – Rob Skelly Oct 26 '15 at 17:06
• You'll likely also want to look at the NGS's HTDP software and connected papers. – mkennedy Oct 27 '15 at 21:28

## 1 Answer

One example is the the International Terrestrial Reference Frame (ITRF). Each ITRF realization provides alongside its transformation parameters also its linear rates of change with respect to the reference epoch. See for instance the ITRF 2014:

http://itrf.ensg.ign.fr/doc_ITRF/Transfo-ITRF2014_ITRFs.txt

I assume these parameters account also for plate tectonics movements .