Projection and CRS Basics
Tutorials to walk you through the basic tools for working with projections and coordinate systems in GIS software.
Some reminders and useful information
The coordinate reference system (CRS) of a map view or data frame is not the same as the CRS of the datasets included within that map or data frame. GIS software reprojects your data on-the-fly to match the CRS that of the map or data frame, whenever possible.
Reprojecting a spatial dataset is the process of assigning a new CRS to a dataset with existing CRS information.
Reprojecting may include a transformation if the original dataset’s datum is different from that of the new CRS. This transformation is built into your software’s projection tool.
If your dataset is missing CRS information, you must define its projection. (Reprojection is not the same as defining the projection of a dataset.) We “define the projection” when a spatial dataset’s CRS information needs to be added. This is the case, for example, if a shapefile is acquired without its associated .prj file. In these cases, consult the file’s metadata to learn which CRS should be defined for the dataset.
ArcGIS Pro
