tweak

core/src/main/java/com/onthegomap/flatmap/geo/GeoUtils.java

@@ -120,22 +120,23 @@ public class GeoUtils {
   }
 
   private static final double QUANTIZED_WORLD_SIZE = Math.pow(2, 31);
+  private static final double HALF_QUANTIZED_WORLD_SIZE = QUANTIZED_WORLD_SIZE / 2;
   private static final long LOWER_32_BIT_MASK = (1L << 32) - 1L;
 
   public static long encodeFlatLocation(double lon, double lat) {
-    double worldX = getWorldX(lon) / 2 + 0.5;
-    double worldY = getWorldY(lat) / 2 + 0.5;
-    long x = (long) (worldX * QUANTIZED_WORLD_SIZE);
-    long y = (long) (worldY * QUANTIZED_WORLD_SIZE);
-    return (x << 32) | y;
+    double worldX = getWorldX(lon) + 1;
+    double worldY = getWorldY(lat) + 1;
+    long x = (long) (worldX * HALF_QUANTIZED_WORLD_SIZE);
+    long y = (long) (worldY * HALF_QUANTIZED_WORLD_SIZE);
+    return (x << 32) | (y & LOWER_32_BIT_MASK);
   }
 
   public static double decodeWorldY(long encoded) {
-    return ((((double) (encoded & LOWER_32_BIT_MASK)) / QUANTIZED_WORLD_SIZE) - 0.5) * 2;
+    return (((double) (encoded & LOWER_32_BIT_MASK)) / HALF_QUANTIZED_WORLD_SIZE) - 1;
   }
 
   public static double decodeWorldX(long encoded) {
-    return ((((double) (encoded >>> 32)) / QUANTIZED_WORLD_SIZE) - 0.5) * 2;
+    return (((double) (encoded >>> 32)) / HALF_QUANTIZED_WORLD_SIZE) - 1;
   }
 
   public static double getZoomFromLonLatBounds(Envelope envelope) {