shrug-l: Lat-Long

Thomas, Jim jim_thomas at
Thu Dec 22 12:00:52 EST 2005

In my opinion, the Export Data tool's purpose is not to be a
re-projection tool, but it can re-project your data to the data frame's
projection during data export.  It saves me time having to go to
ArcToolbox to run a re-projection.  
I can also troubleshoot unknown coordinate systems by changing the data
frame coordinate system.  When my data lines up, I can export it to a
new file using the data frames coordinate system while keeping the old
file in it's original state.


From: Hughes, Ronald [mailto:Ronald.Hughes at] 
Sent: Thursday, December 22, 2005 11:47 AM
To: Thomas, Jim
Cc: shrug-l at
Subject: RE: shrug-l: Lat-Long

Sorry Thomas, but it doesn't re-project.  That method you used simply
re-defines the projection unless they've changed it in Version 9x (which
is highly doubtful).  If you want to change the geometry, you'll need to
use ArcToolbox.  It's simply isn't good practice to assign incorrect
projection files to spatial data.
I hope that clears things up.

From: Thomas, Jim [mailto:jim_thomas at] 
Sent: Thursday, December 22, 2005 11:33 AM
To: Hughes, Ronald
Cc: shrug-l at
Subject: RE: shrug-l: Lat-Long
It's not simply re-defining.  It's re-projecting.  
When you use the 'Export Data...' tool from ArcMap you can select the
export coordinate system (see attached jpg).  It will re-project the
data to what you define.
The Shruggers can use whatever method works best for them.

From: Hughes, Ronald [mailto:Ronald.Hughes at] 
Sent: Thursday, December 22, 2005 11:23 AM
To: Thomas, Jim; shrug-l at
Subject: RE: shrug-l: Lat-Long
Actually Thomas, the problem with that is that the NEW shapefile will
still be in STATEPLANE projection.  In other words, the geometry or
"physical condition" remains as STATEPLANE.  All you've done is
re-define the projection file.  Defining a projection and actually
RE-PROJECTING a shapefile are two separate things.  Re-projecting a
shapefile involves changing its geometry and topology while re-defining
the projection only changes a text file.  You never want to assign an
incorrect projection file to a shapefile because it tends to lead to
trouble if you send that file to somebody else and then they try to
re-project that shapefile using incorrect projection information.  
The reason that it appears to work for you is because of the ArcGIS
"projection on the fly" capability.  If you were to use a GIS product
that doesn't project "on-the-fly" you would see that re-defining the
projection file hasn't changed the geometry of the shapefile: it's still
As far as datum transformation is concerned, when switching between
certain coordinate systems, you may wind up using different datum and
need to transform from one datum to the next.  For example when I was
using ArcGIS version 8x and projected from STATEPLANE NAD83 datum to
Geographic North American 1983 HARN datum I would get the following
error message:

I would then have to set the transformation from NAD_1983 to

Many people think that redefining the projection of a shapefile is the
same and projecting a shapefile but it is not.  I hope that I've
contributed to clearing this up.
Good luck,

From: Thomas, Jim [mailto:jim_thomas at] 
Sent: Thursday, December 22, 2005 10:52 AM
To: Hughes, Ronald; shrug-l at
Subject: RE: shrug-l: Lat-Long
The steps I listed will work too.  You can export a NEW shapefile from
ArcMap in the spatial reference of the data frame (which can be
different than the original shapefile).  As long as everything is
defined correctly, you'll have no problem.  I do it all the time.
As far as the datum transformation list... that's a good question. I
always wondered that.

From: shrug-l-bounces at
[mailto:shrug-l-bounces at] On Behalf Of Hughes,
Sent: Thursday, December 22, 2005 10:32 AM
To: shrug-l at
Subject: RE: shrug-l: Lat-Long
Actually, you need to use ArcToolbox to reproject the shapefile.  All
the steps mention below do is re-define the projection file.  It would
be analogous to assigning a new mailing address to you home without
physically moving it from its current location.  In other words, if your
house sits at 800 Main Street and you change the address to 21 Jump
Street, the house still remains at 800 Main Street.  
The Present version of ArcToolbox that I have (ArcGIS 9.1) is different
from that what I'd previously had but it appears to work the same way.
Open up ArcToolbox and select Data Management Tools --> Projections and
Transformations --> Project. 
Click on Project and a menu should come up that asks for your imput
feature and output (in ArcGIS 9.1 it automatically assigns a 'P' at the
end of the name of the input and places it in the output.  Select the
projection that you want for the output by clicking on the button to the
right of the input window.  That will bring up a menu called "Spatial
Reference Properties".
1.) Click the button labeled "Select".
2.) Click the Geographic Coordinate Systems folder
3.) Click the North America folder and select the coordinate system that
you want (probably North American 1983 HARN.prj).
4.) Click the "Add" button and select "OK".
If you have any other questions just ask.  
Good luck!
-----Original Message-----
From: shrug-l-bounces at
[mailto:shrug-l-bounces at] On Behalf Of Thomas, Jim
Sent: Thursday, December 22, 2005 9:34 AM
To: tdarsey at; shrug-l at
Subject: RE: shrug-l: Lat-Long
1. Define your shapefile's spatial reference in ArcCatalog
2. Load the shapefile into ArcMap
3. Change the data frame spatial reference to Lat/Long
4. Export the new shapefile using the data frame's spatial reference
(during export)
5. That's it.

From: shrug-l-bounces at
[mailto:shrug-l-bounces at] On Behalf Of Tony Darsey
Sent: Thursday, December 22, 2005 9:30 AM
To: shrug-l at
Subject: shrug-l: Lat-Long
Can anyone tell me how to convert a shape file from State Plane to
Tony Darsey 
HSA Consulting Group, Inc. 
1311 Executive Center Drive, Suite 255 
Tallahassee, FL 32301 
Phone (850) 309-7510 
Fax     (850) 309-7510 
Cell     (850) 508-6477 
email   tdarsey at 
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