I have done a ton of research on the most accurate transformation to use in mainland Alaska to convert between the NAD83 and WGS84 datums, but I just can't seem to find a definitive answer.
ArcMap gives 3 options for my area of interest:
- This one I am really unsure of and I have not found much information on when it should be used. I know it has something to do with epochs or realizations of datums, but I am in over my head on this one. Can someone please enlighten me?
- This is the one I think might be most applicable, but I am unable to find any definitive information to say whether or not it should be used for Alaska.
- Esri says it is applicable for Alaska, but I can't find confirmation of this anywhere else
- EPSG doesn't list this transformation when I search with coordinates in Alaska (or at all for that matter)
- I am fairly certain that this is a "null" transformation that doesn't actually do anything, and would therefore be least accurate. Especially in Alaska where everything shifts with time.
I should also note that we are using NAD83 (NSRS 2007) in our geodatabase and converting GPS survey data from WGS84 to NAD83 (NSRS 2007) with a custom transformation developed by a geodesist for our area of interest which shifts everything by a meter or so in x and y (the Esri transformation for this is a null transformation that doesn't actually do anything). What I am trying to do is load legacy/reference data that is currently in NAD83 by first transforming to WGS84 (my question here) and then transforming to NAD83 (NSRS 2007) via our custom transformation.
I need to define a definitive procedure for the project team to follow and it will be used on potentially hundreds of layers so I need to get it right.