Manage geometry metadata

Set the active geometry column and CRS before writing a table whose column names or coordinate metadata differ from GeoDataFrames' defaults.

Set metadata on a DataFrame

setgeometrycolumn! records which column contains geometries. setcrs! records the coordinate reference system.

using GeoDataFrames
using GeoDataFrames: setcrs!, setgeometrycolumn!

locations = DataFrame(
    label = ["library"],
    shape = GeoInterface.Point.([(4.8952, 52.3702)]),
)
setgeometrycolumn!(locations, :shape)
setcrs!(locations, EPSG(4326))

(geometrycolumns = GeoInterface.geometrycolumns(locations), crs = GeoInterface.crs(locations))

(geometrycolumns = (:shape,), crs = EPSG{1}((4326,)))

setcrs! assigns a CRS label. It does not transform coordinate values. Use reproject when coordinates must change.

Provide metadata only for one write

When a table cannot store metadata, pass the geometry column and CRS to write:

anonymous_locations = DataFrame(
    label = ["station"],
    shape = GeoInterface.Point.([(4.9000, 52.3790)]),
)

mktempdir() do directory
    GeoDataFrames.write(
        joinpath(directory, "locations.gpkg"),
        anonymous_locations;
        geometrycolumn = :shape,
        crs = EPSG(4326),
    )
end

"/tmp/jl_zV9q0Q/locations.gpkg"

This write-level metadata does not change anonymous_locations. For metadata formats and retrieval details, see the metadata reference and metadata and CRS background.