From 6ec8f7eaa75ac7215010985c48136651a4150936 Mon Sep 17 00:00:00 2001
From: duminil <duminil@2c044af0-2e85-064f-a0c3-7471430cffcd>
Date: Fri, 19 May 2017 13:18:58 +0000
Subject: [PATCH] RegionChooser: Relatively fast and efficient convex hull
extractor from CityGML files.
---
.../regionchooser/ConvexHullCalculator.java | 29 ++++++++++++++++---
.../test/ConvexHullCalculatorTests.java | 3 +-
2 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/src/eu/simstadt/regionchooser/ConvexHullCalculator.java b/src/eu/simstadt/regionchooser/ConvexHullCalculator.java
index ccb016d..45358ed 100644
--- a/src/eu/simstadt/regionchooser/ConvexHullCalculator.java
+++ b/src/eu/simstadt/regionchooser/ConvexHullCalculator.java
@@ -3,6 +3,10 @@
import java.io.IOException;
import java.nio.file.Path;
import java.util.ArrayList;
+import org.osgeo.proj4j.BasicCoordinateTransform;
+import org.osgeo.proj4j.CRSFactory;
+import org.osgeo.proj4j.CoordinateReferenceSystem;
+import org.osgeo.proj4j.ProjCoordinate;
import com.vividsolutions.jts.algorithm.ConvexHull;
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Geometry;
@@ -16,10 +20,10 @@
public class ConvexHullCalculator
{
- //TODO: Convert coordinates to WGS84
public static Geometry calculateFromCityGML(Path citygmlPath)
throws NumberFormatException, XPathParseException, NavException, XPathEvalException, IOException {
+ GeometryFactory geometryFactory = new GeometryFactory();
ArrayList<Coordinate> allPoints = new ArrayList<Coordinate>();
CityGmlIterator citygml = new CityGmlIterator(citygmlPath);
for (BuildingXmlNode buildingXmlNode : citygml) {
@@ -30,8 +34,25 @@ public static Geometry calculateFromCityGML(Path citygmlPath)
}
ConvexHull ch = new com.vividsolutions.jts.algorithm.ConvexHull(
- allPoints.toArray(new Coordinate[allPoints.size()]), new GeometryFactory());
- return ch.getConvexHull();
- }
+ allPoints.toArray(new Coordinate[allPoints.size()]), geometryFactory);
+
+ // Convert convex hull in original coordinates to WGS84 coordinates.
+ // NOTE: It would be much easier with import org.geotools.referencing.CRS; instead of Proj4J
+ // NOTE: It's faster to convert to WGS84 once the convex hull is calculated, because there are fewer points
+ Coordinate[] convexHullcoordinates = ch.getConvexHull().getCoordinates();
+
+ CRSFactory CRS_FACTORY = new CRSFactory();
+ CoordinateReferenceSystem wgs84 = CRS_FACTORY.createFromName("EPSG:4326");
+ CoordinateReferenceSystem originalCRS = citygml.getCRS();
+ BasicCoordinateTransform transformToWgs84 = new BasicCoordinateTransform(originalCRS, wgs84);
+ for (int i = 0; i < convexHullcoordinates.length; i++) {
+ ProjCoordinate wgs84Coordinate = transformToWgs84.transform(
+ new ProjCoordinate(convexHullcoordinates[i].x, convexHullcoordinates[i].y),
+ new ProjCoordinate());
+ convexHullcoordinates[i] = new Coordinate(wgs84Coordinate.x, wgs84Coordinate.y);
+ }
+
+ return geometryFactory.createPolygon(convexHullcoordinates);
+ }
}
diff --git a/test/eu/simstadt/regionchooser/test/ConvexHullCalculatorTests.java b/test/eu/simstadt/regionchooser/test/ConvexHullCalculatorTests.java
index 72485f7..59fa855 100644
--- a/test/eu/simstadt/regionchooser/test/ConvexHullCalculatorTests.java
+++ b/test/eu/simstadt/regionchooser/test/ConvexHullCalculatorTests.java
@@ -22,8 +22,7 @@ public void testExtractConvexHullFromOneBuilding() throws Throwable {
Path citygmlPath = repo.resolve("Gruenbuehl.proj/20140218_Gruenbuehl_LOD2_1building.gml");
Geometry hull = ConvexHullCalculator.calculateFromCityGML(citygmlPath);
assertEquals(hull.getCoordinates().length, 4 + 1); // Convex hull of a building should be a closed rectangle
- // Point someBuildingPoint = gf.createPoint(new Coordinate(3515960.36, 5415667.91)); // Original coordinates, GSK3
- Point someBuildingPoint = gf.createPoint(new Coordinate(9.21656126408, 48.8782253597)); // WGS84
+ Point someBuildingPoint = gf.createPoint(new Coordinate(9.216845, 48.878196)); // WGS84
assertTrue("Hull should contain every building point", hull.contains(someBuildingPoint));
}
--
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