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ITRF epoch in compound NAD transformation

Question asked by joeb@cwd on Mar 30, 2016
Latest reply on Apr 18, 2018 by MKennedy-esristaff

Hello,

 

Another GIS specialist up to my neck in Coordinate System information here.

 

I have a number of questions related to the current realization of WGS1984(G1674).

 

When transforming between NAD83 (2011) and the original NAD83 (1986 or "CONUS") in ArcMap, compound transformations are listed. I understand this (transform to WGS/ITRF first and then back into the other NAD83 Epoch given the defined NGS conversion values). But in 10.4, the most suitable listed transformation is "WGS_1984_(ITRF00)_To_NAD_1983 + WGS_1984_(ITRF08)_To_NAD_1983_2011". Shouldn't the epoch of each WGS reference frame match? I don't see a choice for ITRF08_To_NAD83 + ITRF08_To_NAD83_2011. There is a choice for "WGS_1984_(ITRF00)_To_NAD_1983 + WGS_1984_(ITRF00)_To_NAD_1983_2011", but it is down the list in suitability, below the HARN transformations.

 

I consulted the NAD_1983_To_WGS_1984 knowledge base article here: 24159 - Determine which NAD_1983_To_WGS_1984 transformation to use, and I can see that the "WGS_1984_(ITRF08)_To_NAD_1983_2011" transformation is the most accurate (0.030 m versus 0.100 m for ITRF00). But it is not listed for use in the USA, only for the Pacific Ocean. I'm in California (State Plane Zn 2), so maybe that's fine? There is not a "WGS_1984_(ITRF08)_To_NAD_1983" (epoch 1986) transformation listed to be used in the second half of the compound transformation I need to perform. Is that because it is not currently defined by NGS?

 

Thanks in advance.

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