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#369 monitor vector tiles poc - improve tile coordinate calculation
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69 changes: 69 additions & 0 deletions
69
server/src/main/scala/kpn/server/analyzer/engine/tiles/domain/CoordinateTransform.scala
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,69 @@ | ||
| package kpn.server.analyzer.engine.tiles.domain | ||
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| import org.locationtech.jts.geom.Coordinate | ||
| import org.locationtech.jts.geom.LineString | ||
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| import scala.math.Pi | ||
| import scala.math.atan | ||
| import scala.math.exp | ||
| import scala.math.log | ||
| import scala.math.sin | ||
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| /* | ||
| EPSG:4326 | ||
| WGS84 reference system used by OSM | ||
| See: https://en.wikipedia.org/wiki/Mercator_projection | ||
| coordinates | ||
| longitude (x) | ||
| latitude (y) | ||
| EPSG:3857 | ||
| reference system WGS84 Web Mercator used in tiles | ||
| See: https://en.wikipedia.org/wiki/Web_Mercator_projection | ||
| world coordinates | ||
| worldX | ||
| The longitude for a web mercator coordinate where 0 is the international | ||
| date line on the west side, 1 is the international date line on the east | ||
| side, and 0.5 is the prime meridian. | ||
| worldY | ||
| The latitude for a web mercator coordinate where 0 is the north edge of | ||
| the map, 0.5 is the equator, and 1 is the south edge of the map. | ||
| */ | ||
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| object CoordinateTransform { | ||
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| private val DEGREES_PER_RADIAN = 180 / Pi | ||
| private val RADIANS_PER_DEGREE = Pi / 180 | ||
| private val MAX_LAT = worldYtoLat(-0.1) | ||
| private val MIN_LAT = worldYtoLat(1.1) | ||
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| def worldXtoLon(worldX: Double): Double = { | ||
| worldX * 360 - 180 | ||
| } | ||
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| def worldYtoLat(worldY: Double): Double = { | ||
| val n = Pi - 2 * Pi * worldY | ||
| DEGREES_PER_RADIAN * atan(0.5 * (exp(n) - exp(-n))) | ||
| } | ||
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| def lonToWorldX(lon: Double): Double = { | ||
| (lon + 180) / 360 | ||
| } | ||
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| def latToWorldY(lat: Double): Double = { | ||
| if (lat <= MIN_LAT) return 1.1 | ||
| if (lat >= MAX_LAT) return -0.1 | ||
| val sinus = sin(lat * RADIANS_PER_DEGREE) | ||
| 0.5 - 0.25 * log((1 + sinus) / (1 - sinus)) / Pi | ||
| } | ||
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| def toWorldCoordinates(lineString: LineString): Array[Coordinate] = { | ||
| (0 until lineString.getNumPoints).toArray.map { index => | ||
| val point = lineString.getPointN(index) | ||
| val x = lonToWorldX(point.getX) | ||
| val y = latToWorldY(point.getY) | ||
| new Coordinate(x, y) | ||
| } | ||
| } | ||
| } |
34 changes: 34 additions & 0 deletions
34
server/src/main/scala/kpn/server/analyzer/engine/tiles/domain/NewTile.scala
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| @@ -0,0 +1,34 @@ | ||
| package kpn.server.analyzer.engine.tiles.domain | ||
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| import org.locationtech.jts.geom.Coordinate | ||
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| class NewTile(val z: Int, val x: Int, val y: Int) { | ||
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| val name: String = s"$z-$x-$y" | ||
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| private val zoomFactor = 1 << z // the number of tiles across the map in each direction | ||
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| private val worldXMin = x.toDouble / zoomFactor | ||
| private val worldXMax = (x.toDouble + 1) / zoomFactor | ||
| private val worldYMin = y.toDouble / zoomFactor | ||
| private val worldYMax = (y.toDouble + 1) / zoomFactor | ||
| private val worldWidth = worldXMax - worldXMin | ||
| private val worldHeight = worldYMax - worldYMin | ||
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| override def equals(obj: Any): Boolean = { | ||
| obj.isInstanceOf[Tile] && obj.asInstanceOf[Tile].name == name | ||
| } | ||
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| override def hashCode(): Int = name.hashCode() | ||
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| def scale(worldCoordinates: Seq[Coordinate]): Seq[Coordinate] = { | ||
| worldCoordinates.map(scale) | ||
| } | ||
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| def scale(coordinate: Coordinate): Coordinate = { | ||
| val scaledX = ((coordinate.x - worldXMin) * 256 / worldWidth) | ||
| val scaledY = ((coordinate.y - worldYMin) * 256 / (worldHeight)) | ||
| new Coordinate(scaledX, scaledY) | ||
| } | ||
| } |
25 changes: 25 additions & 0 deletions
25
server/src/test/scala/kpn/server/analyzer/engine/tiles/domain/CoordinateTransformTest.scala
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,25 @@ | ||
| package kpn.server.analyzer.engine.tiles.domain | ||
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| import kpn.core.util.UnitTest | ||
| import kpn.server.analyzer.engine.tiles.domain.CoordinateTransform.worldYtoLat | ||
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| class CoordinateTransformTest extends UnitTest { | ||
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| test("coordinate transform") { | ||
| assertTransform(0, 0, 0.5, 0.5) | ||
| assertTransform(0, -180, 0, 0.5) | ||
| assertTransform(0, 180, 1, 0.5) | ||
| assertTransform(0, 180 - 1e-7, 1, 0.5) | ||
| assertTransform(45, 0, 0.5, 0.3597) | ||
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| worldYtoLat(-0.1) should equal(87.35 +- 0.01) | ||
| worldYtoLat(1.1) should equal(-87.35 +- 0.01) | ||
| } | ||
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| private def assertTransform(lat: Double, lon: Double, worldX: Double, worldY: Double): Unit = { | ||
| CoordinateTransform.latToWorldY(lat) should equal(worldY +- 0.0001) | ||
| CoordinateTransform.lonToWorldX(lon) should equal(worldX +- 0.0001) | ||
| CoordinateTransform.worldYtoLat(worldY) should equal(lat +- 0.01) | ||
| CoordinateTransform.worldXtoLon(worldX) should equal(lon +- 0.01) | ||
| } | ||
| } |