Metadata and CRS

For DataFrames, GeoDataFrames stores spatial table metadata under these keys:

Key	Value
"GEOINTERFACE:geometrycolumns"	A tuple of geometry-column symbols
"GEOINTERFACE:crs"	The coordinate reference system, or nothing

Use GeoInterface.geometrycolumns(table) to retrieve the geometry columns and GeoInterface.crs(table) to retrieve the CRS. For a DataFrame, set the values with:

setgeometrycolumn!(df, :geometry)
setgeometrycolumn!(df, (:geometry, :centroid))
setcrs!(df, crs)

setcrs! assigns metadata; it does not transform coordinates. Use reproject! when coordinates must be transformed.

Writing

ArchGDALDriver obtains its default geometrycolumn and crs values from this metadata. Its explicit geometrycolumn and crs keywords override those defaults. Other drivers support different write keywords; consult the native-driver reference or the ArchGDAL driver reference.

For the rationale for this metadata representation, see Metadata and CRS background.