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Good morning,

I will try to make this as understandable as possible:

Objective:  To show why proper metadata (datum/realization wise) is
important.

I got the datasheet for a geodetic control point in NJ.  It has a current
NAD 83(2011) lat/lon.  It also has many superseded coordinates (Lat/Lon)
going all the way back to NAD 83(1986).

I created a map in ArcMap, and established the data frame coordinate
reference to be NAD 83(2011)

I then created a .txt file of the various NAD 83 positions that reflected
the various realizations 2011, 2007, 1996, 1992, 1986.

I added the xy data to the map and told ArcMap that they were Geographic
NAD 83 (2011) (which of course they were not).  As one would expect, I got
5 dots on the map with a spatial separation that reflected the differences
between the 5 realizations.

Next I created one file for each coordinate, and added each file one at a
time.  This time, I told ArcMap that the coordinate system for each file
was actual realization of the position, i.e., when adding the NAD 83(2007)
lat and lon, I told ArcMap that the coordinate system of the position was
in fact NAD 83(2007).  The result was 5 dots that plotted exactly on top of
the other 5 dots, i.e., no transformation took place?

Am I doing something wrong?

Thanks for any input.  I have attached the files if anyone wants to test
this them selves.  I have provided the files to some of my counterparts and
they experienced the same.

Dan


Daniel J. Martin
Northeast Regional Geodetic Advisor
(ME, NH, VT, MA, CT, RI, NY, NJ)
NOAA/NOS/National Geodetic Survey

Email: [log in to unmask]
Cell:    240-676-4762

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