shrug-l: Lat-Long

Thomas, Jim jim_thomas at golder.com
Thu Dec 22 12:45:27 EST 2005


1. When you 'clear' data frame's coordinate system, there is no 'project
on the fly' because ArcMap doesn't know what to project any of the data
to.  My data was in two different places, which proves that the geometry
changed.
 
2. Alan Elebash added... "If your data's geographic coordinate system
<blocked::javascript:glossary_geographic_coordinate_system22168.Click()>
uses a different datum <blocked::javascript:glossary_datum22168.Click()>
than that of the new feature class, you will likely write spatially
inaccurate data." This is where datum transformation comes in to play.
There's no guarantee that the Export tool will transform datum
correctly.
 
3. Alan's email also stated:  "When you export data from ArcMap, you can
choose to create a new feature class
<javascript:glossary_feature_class22168.Click()>  using a different
coordinate system than that of the source data..." The tool does not
simply re-define.
 
One thing is certain.  A geometric change does occur.  
 
I won't tie up the Shrug members any longer with this issue today.
 
 

________________________________

From: Hughes, Ronald [mailto:Ronald.Hughes at dep.state.fl.us] 
Sent: Thursday, December 22, 2005 12:32 PM
To: Thomas, Jim; Paulsen, Janis
Cc: shrug-l at lists.dep.state.fl.us
Subject: RE: shrug-l: Lat-Long


Thomas I'll repeat it one more time.  If you bring it into another GIS
product that doesn't "project on the fly", you will see that the
geometry has not changed.  That's is what Janis did.
 
Just a moment ago, you said that the Export Data Tool IS NOT a
re-projection tool, but now you are saying that it IS and you were
correct the whole time?  I'm not sure what your datum argument is either
since I've already explained datum transformation.  
 
________________________________

From: Thomas, Jim [mailto:jim_thomas at golder.com] 
Sent: Thursday, December 22, 2005 12:23 PM
To: Hughes, Ronald; Paulsen, Janis
Cc: shrug-l at lists.dep.state.fl.us
Subject: RE: shrug-l: Lat-Long
 
I've tested my theory - the Export Data tool created a brand new
shapefile in a completely different geometry consistent with the data
frame's coordinate system (i tested this by 'clearing' the data frame
coordinate system - that's the same as bringing the two datasets into
ArcView GIS).  My point is that the Export Data tools will re-project.
Although, is appears there is no guarantee that it will transform the
datums correctly... "If your data's 
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