I agree with Keith

On Wed, Oct 10, 2018, 10:46 AM Miller, Keith <[log in to unmask]> wrote:

I may be showing my ignorance here, but I would think that the fact that the five different lat longs all plotting at the same point showed that there WERE transformations taking place. If the “points” were supposed to represent the same physical location on the earth, then they SHOULD all overlap, as long as you tell ArcGIS the proper coordinate system used, which is what it sounds like you did in the second step. The first step showed the problem with not having proper documentation, in that the same “point” showed up in five different places on the map. What am I missing?

 

Sincerely,

Keith Miller

 

From: Northeast Arc Users Group [mailto:[log in to unmask]] On Behalf Of Christina Herrick
Sent: Wednesday, October 10, 2018 10:49 AM
To: [log in to unmask]
Subject: Re: Transforming xy data

 

I'd be curious to know if anyone figures this out.  I gave it a try and I'm also having the same issues.  

Christina Herrick

Research Scientist

V: 603.862.2639 | F: 603.862.0188

University of New Hampshire

Institute for the Study of Earth, Oceans, and Space

Earth Systems Research Center

Morse Hall, 8 College Road

Durham, NH 03824

 

ResearcherID:              O-3375-2017

ORCID ID: 0000-0002-8384-9450

 

 

 

On Wed, Oct 10, 2018 at 10:19 AM Dan Martin - NOAA Federal <[log in to unmask]> wrote:

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  It also has many superseded coordinates (Lat/Lon) going all the way back to NAD 83(1986).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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