Monday, June 14, 2010

Calculating Convex Hull and Minimum Bounding Circle with Groovy

The Java Topology Suite, which Groovy GeoScript wraps, contains spatial operators that act on a group of Features or Geometries. In this post, I collect all geometries from a shapefile to calculate the convex hull and minimum bounding circle. This post builds on previous blog entries where I use GeoScript to extract centroids and buffer Features.

Convex Hull
// Import GeoScript modules
import geoscript.layer.*
import geoscript.feature.*
import geoscript.geom.*

// Get the shapefile
Shapefile shp = new Shapefile('states_centroids.shp');

// Create a new Schema
Schema schema = new Schema('states_convex_hull', [['the_geom','Polygon','EPSG:4326']])

// Create our new Layer
Layer layer = shp.workspace.create(schema)

// Collect the Geometries
List geoms = shp.features.collect{f->f.geom}

// Create a GeometryCollection from the List of Geometries
GeometryCollection geomCol = new GeometryCollection(geoms)

// Get the Convex Hull from the GeometryCollection
Geometry convexHullGeom = geomCol.convexHull

// Add the Convex Hull Geometry as a Feature
layer.add(schema.feature([convexHullGeom]))



Minimum Bounding Circle

// Import GeoScript modules
import geoscript.layer.*
import geoscript.feature.*
import geoscript.geom.*

// Get the Shapefile
Shapefile shp = new Shapefile('states_centroids.shp')

// Create a new Schema
Schema schema = new Schema('states_minimum_bounding_circle', [['the_geom','Polygon','EPSG:4326']])

// Create the new Layer
Layer layer = shp.workspace.create(schema)

// Collect Geometries from the Shapefile
List geoms = shp.features.collect{f->f.geom}

// Create a GeometryCollection from the List of Geometries
GeometryCollection geomCol = new GeometryCollection(geoms)

// Get the Minimum Bounding Circle from the GeometryCollection
Geometry circleGeom = geomCol.minimumBoundingCircle

// Add the Minimum Bounding Circle Geometry as a Feature
layer.add(schema.feature([circleGeom]))

1 comment:

  1. Jared (or anyone for that matter),

    Are you aware of any implementations of the Douglas-Peucker or Lang Simplification algorithms in Groovy? Alternatively what about Java? I can port one over from C++ or other language but I'd hate to reinvent the wheel! TIA for any help.

    ReplyDelete

Introducing GeoScript

GeoScript adds geo capabilities to dynamic scripting languages such as JavaScript, Python, Scala and Groovy.