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

Blog Post created by spk578 on Aug 19, 2014

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 ArcGIS ArcView Trai…