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How it works

GIS data as a DataFrame

SimpleFeatures reads vector GIS data from files and creates a DataFrame containing geometries and their attributes.

Each row is a feature, and geometry data for each feature are stored in the geom column.

Example:

1000×2 DataFrame
  Row │ geom                          lyr.1 
      │ sfgeom                        Int32 
──────┼─────────────────────────────────────
    1 │ POLYGON ((853787 3905499,...      1
    2 │ POLYGON ((853800 3905499,...      1
    3 │ POLYGON ((853803 3905499,...      1
  ⋮   │              ⋮                  ⋮
  998 │ POLYGON ((904045 3905468,...      1
  999 │ POLYGON ((905355 3905468,...      1
 1000 │ POLYGON ((905561 3905469,...      1
                            994 rows omitted

Metadata: crs and geomtype

These metadata (.crs, .geomtype) are stored as a attributes within a SimpleFeature object and can be modified or accessed directly.

Example::

x.crs 

GeoFormatTypes.WellKnownText2{GeoFormatTypes.Unknown}(GeoFormatTypes.Unknown(), "PROJCRS[\"NAD83(2011) / UTM zone 17N\",BASEGEOGCRS[\"NAD83(2011)\",DATUM[...
x.geomtype

wkbPolygon::OGRwkbGeometryType = 3

Types:

Geometries as sfgeom objects

Each row of the geom column is an sfgeom object that has two attributes:

  • wkb: A vector (type Vector{UInt8}) of the Well-known binary (WKB) representation of the geometry.

    Example: julia 93-element Vector{UInt8}: 0x01 0x03 0x00 0x00 0x00 ⋮ 0x80 0xed 0xcb 0x4d 0x41

  • preview: A string that shows an abbreviated Well-known text (WKT) string.

    Example:

    julia POLYGON ((853787 3905499,...

This data structure allows SimpleFeatures to:

  • interface with GDAL and GEOS for fast I/O and operations (using using ArchGDAL.jl and LibGEOS.jl, respectively)
  • provide a preview of the geometry's WKT for viewing
  • represent geometries (wkb) in Julia without needing to define a new SimpleFeatures type for each type of geometry. SimpleFeatures uses ArchGDAL geometry types for geometry type info and follows the GeoInterface standard.

This package builds on existing Julia GIS packages GeoDataFrames and ArchGDAL.