adjust styling zoom based on latitude, close #192

mapbox · Mar 27, 2014 · 71d36c3 · 71d36c3
1 parent 771d120
commit 71d36c3
Showing 1 changed file with 12 additions and 3 deletions.
diff --git a/js/ui/map.js b/js/ui/map.js
@@ -421,9 +421,18 @@ util.extend(Map.prototype, {
     },
 
     _updateStyle: function() {
-        if (this.style) {
-            this.style.recalculate(this.transform.zoom);
-        }
+        if (!this.style) return;
+
+        // adjust zoom value based on latitude to compensate for Mercator projection distortion;
+        // start increasing adjustment from 0% at zoom 7 to 100% at zoom 9
+
+        var zoom = this.transform.zoom,
+            scale = this.transform.scaleZoom(1 / Math.cos(this.transform.center.lat * Math.PI / 180)),
+            minAdjustZoom = 6,
+            maxAdjustZoom = 9,
+            multiplier = Math.min(Math.max(zoom - maxAdjustZoom, 0) / (maxAdjustZoom - minAdjustZoom), 1);
+
+        this.style.recalculate(zoom + scale * multiplier);
     },
 
     _updateBuckets: function() {