When should I use the Define Projection tool and the Project tool?

08-19-2014 12:26 PM
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There are two tools in ArcGIS Desktop associated with using coordinate reference systems that often cause confusion. I believe these confusions are mainly sourced from the semantics surrounding projections and the tools in question.

The tools are the Define Projection and Project tools.


In a nut shell...

Define Projection: This tool overwrites the coordinate system information in a dataset

This means only use the Define Projection tool on a dataset that has no coordinate system applied or to a dataset you know for certain has the wrong projection.

Project: This tool projects a dataset from one coordinate system to another through transformation or conversion

Use the Project tool when you want to convert a dataset from one coordinate system to another. For example when converting from ED_50_UTM_31N to ED_50_UTM_30N or when transforming between ED_50_UTM_31N and WGS84_UTM_31N

For more information check out these resources...

Exprodat Blog !@

ArcGIS Help

Support Services Blog

GIS Geek

Have a look at a related course to learn more on managing and working with coordinate reference systems with ArcGIS:

ArcGIS Coordinate Reference Systems for Petroleum | CRS Spatial Reference Petroleum Oil Gas Industry...

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About the Author
Geologist, Geospatial Expert and TAP Certified GIS Trainer working as an Independant Consultant. I have special interests in Geology, Exploration, Coordinate Reference Systems, Geodesy and Natural Science.