From 6caed761011801718b356c7cebae3f9117c0ac9a Mon Sep 17 00:00:00 2001
From: Tobias Zwick <osm@westnordost.de>
Date: Mon, 27 Jan 2020 15:36:19 +0100
Subject: [PATCH] gps range also precise when tilting the map (#1684)

---
 .../map/LocationAwareMapFragment.kt           | 22 ++++++-------------
 .../util/SphericalEarthMath.java              |  2 ++
 2 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/app/src/main/java/de/westnordost/streetcomplete/map/LocationAwareMapFragment.kt b/app/src/main/java/de/westnordost/streetcomplete/map/LocationAwareMapFragment.kt
index 897642fa46..549da69aa3 100644
--- a/app/src/main/java/de/westnordost/streetcomplete/map/LocationAwareMapFragment.kt
+++ b/app/src/main/java/de/westnordost/streetcomplete/map/LocationAwareMapFragment.kt
@@ -187,25 +187,17 @@ open class LocationAwareMapFragment : MapFragment() {
         val location = displayedLocation ?: return
         if (accuracyMarker?.isVisible != true) return
 
-        val pos = OsmLatLon(location.latitude, location.longitude)
-        val size = meters2Pixels(pos, location.accuracy)
+        val zoom = controller!!.cameraPosition.zoom
+        val size = location.accuracy * pixelsPerMeter(location.latitude, zoom)
         accuracyMarker?.setStylingFromString(
-            "{ style: 'points', color: 'white', size: [${size}px, ${size}px], order: 2000, flat: true, collide: false }"
+            "{ style: 'points', color: 'white', size: ${size}px, order: 2000, flat: true, collide: false }"
         )
     }
 
-    private fun meters2Pixels(at: LatLon, meters: Float): Float {
-        val pos0 = at
-        val pos1 = SphericalEarthMath.translate(pos0, meters.toDouble(), 0.0)
-        val screenPos0 = controller!!.latLonToScreenPosition(pos0)
-        val screenPos1 = controller!!.latLonToScreenPosition(pos1)
-        val camera = controller!!.cameraPosition
-        val tiltFactor = (sin(camera.tilt / 2.0) * cos(camera.rotation)).toFloat()
-        return (1f / (1f - abs(tiltFactor)) *
-                sqrt(
-                    (screenPos1.y - screenPos0.y).pow(2f) +
-                    (screenPos1.x - screenPos0.x).pow(2f)
-                ))
+    private fun pixelsPerMeter(latitude: Double, zoom: Float): Double {
+        val numberOfTiles = (2.0).pow(zoom.toDouble())
+        val metersPerTile = cos(latitude * PI / 180.0) * SphericalEarthMath.EARTH_CIRCUMFERENCE / numberOfTiles
+        return 256 / metersPerTile
     }
 
     /* --------------------------------- Position tracking -------------------------------------- */
diff --git a/app/src/main/java/de/westnordost/streetcomplete/util/SphericalEarthMath.java b/app/src/main/java/de/westnordost/streetcomplete/util/SphericalEarthMath.java
index 337db7a6e3..ef955e17d8 100644
--- a/app/src/main/java/de/westnordost/streetcomplete/util/SphericalEarthMath.java
+++ b/app/src/main/java/de/westnordost/streetcomplete/util/SphericalEarthMath.java
@@ -19,6 +19,8 @@ public class SphericalEarthMath
 	 */
 	public static final double EARTH_RADIUS = 6371000;
 
+	public static final double EARTH_CIRCUMFERENCE = 40000000;
+
 	/**
 	 * Calculate a bounding box that contains the given circle. In other words, it is a square
 	 * centered at the given position and with a side length of radius*2.