LibGEOS.jl

LibGEOS is a package for manipulation and analysis of planar geometric objects, based on the libraries GEOS (the engine of PostGIS) and JTS (from which GEOS is ported). This package wraps the GEOS C API, see its usage and reference docs.

Among other things, it allows you to parse Well-known Text (WKT).

p1 = readgeom("POLYGON((0 0,1 0,1 1,0 0))")
p2 = readgeom("POLYGON((0 0,1 0,1 1,0 1,0 0))")
p3 = readgeom("POLYGON((2 0,3 0,3 1,2 1,2 0))")

Add a buffer around them

g1 = buffer(p1, 0.5)
g2 = buffer(p2, 0.5)
g3 = buffer(p3, 0.5)

and take the union of different geometries

polygon = LibGEOS.union(g1, g3)

GEOS functionality is extensive, so coverage is incomplete, but the basic functionality for working with geospatial data is already available. I'm learning as I go along, so documentation is lacking, but if you're interested, you can have a look at the examples in the examples/ folder, or the tests in test/test_geo_interface.jl and test/test_geos_operations.jl.

Conversion to/from GeoInterface objects

GeoInterface.jl compatible geometries from many packages including GeometryBasics.jl, Shapefile.jl, GeoJSON.jl, KML.jl, ArchGDAL.jl, GADM.jl and others can be easily converted to LibGEOS geometries using:

GeoInterface.convert(LibGEOS, other_package_geometry)

To broadcast this over a vector or iterable we need to use Ref on LibGEOS:

GeoInterface.convert.(Ref(LibGEOS), iterable_of_geometries)

The same applies in reverse, such as for interop with the Makie.jl/GeometryBasics.jl ecosystem:

GeoInterface.convert(GeometryBasics, libgeos_geometry)

For packages like Shapefile.jl and GeoJSON.jl, converting to their objects isn't possible, as theyre not particularly useful on their own. Instead, we can just write directly:

Shapefile.write("myfile.shp", libgeos_geometry)

GeoInterface methods

GeoInterace.jl OGC standards methods work on LibGEOS objects:

• GeoInterface.distance
• GeoInterface.buffer
• GeoInterface.convexhull
• GeoInterface.equals
• GeoInterface.disjoint
• GeoInterface.intersects
• GeoInterface.touches
• GeoInterface.within
• GeoInterface.contains
• GeoInterface.overlaps
• GeoInterface.crosses
• GeoInterface.symdifference
• GeoInterface.difference
• GeoInterface.intersection
• GeoInterface.union

See the GeoInterface.jl API docs for details.

Exported LibGEOS geometries:

• GeometryCollection
• LineString
• LinearRing
• MultiLineString
• MultiPoint
• MultiPolygon
• Point
• Polygon
• STRtree

Exported LibGEOS functions:

• area
• boundary
• buffer
• bufferWithStyle
• centroid
• constrainedDelaunayTriangulation
• containsproperly
• convexhull
• coveredby
• covers
• crosses
• delaunayTriangulation
• delaunayTriangulationEdges
• difference
• disjoint
• distance
• endPoint
• envelope
• equals
• equalsexact
• exteriorRing
• geomLength
• getGeometries
• getGeometry
• getPrecision
• getXMax
• getXMin
• getYMax
• getYMin
• hasZ
• hausdorffdistance
• interiorRing
• interiorRings
• interpolate
• interpolateNormalized
• intersection
• intersects
• isClosed
• isEmpty
• isRing
• isSimple
• isValid
• lineMerge
• minimumRotatedRectangle
• nearestPoints
• node
• numGeometries
• numPoints
• overlaps
• pointOnSurface
• polygonize
• prepareGeom
• project
• projectNormalized
• query
• readgeom
• setPrecision
• sharedPaths
• simplify
• snap
• startPoint
• symmetricDifference
• topologyPreserveSimplify
• touches
• unaryUnion
• union
• uniquePoints
• within
• writegeom

Installation

1. At the Julia prompt, run

   pkg> add LibGEOS

   This will install both the Julia package and GEOS shared libraries together. The GEOS build comes from GEOS_jll, and the build script can be found in Yggdrasil.

2. Test that LibGEOS works by runnning

   pkg> test LibGEOS

   Ecosystem

   • All GeoInterface.jl compatible geometries will work in LibGEOS without conversion.
   • Makie support for LibGEOS is available via LibGEOSMakie.jl
   • LibGEOS integrates with GeoInterface.jl making it easy to combine LibGEOS with other geometry packages.