Define Projection vs Project... a visual guide

09-06-2016 11:57 PM
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There is ... still ... confusion regarding the proper use of the  Define Projection Tool versus the Project Tool

"my data don't line up..."

"I am sure about the coordinate system..."

"everything is far apart onscreen..."

We have all been there.  The written descriptions don't seem to catch on, so a visual guide might be what is needed.

Prior to proceeding... make sure you have seen the ...References... at the end of this section... that is what you need to understand.

So with tongue firmly planted in cheek...

Existing coordinate systemDesired coordinate systemTool to useResult

Project Tool 

Project Tool

Wrong Geographic Transformation

Define Projection Tool

The choice really depends on:

  • what you know you have... not what you think you have...
  • what you really need...
  • applying the correct tool...   if it doesn't work out, undo what you did... locate the originals... read the metadata
  • understanding what you got and why.


And to cover some of the other combinations and permutations, just remember....things can get worse, before they get better...

About the Author
Retired Geomatics Instructor at Carleton University. I am a forum MVP and Moderator. Current interests focus on python-based integration in GIS. See... Py... blog, my GeoNet blog...