diff --git a/lib/map.js b/lib/map.js
index 23dcd22..665b8bb 100644
--- a/lib/map.js
+++ b/lib/map.js
@@ -9,7 +9,7 @@ define(['map/clientlayer', 'map/labelslayer',
       zoomControl: false
     };
 
-    var LocateButton = L.Control.extend({
+    var ButtonBase = L.Control.extend({
       options: {
         position: 'bottomright'
       },
@@ -22,6 +22,17 @@ define(['map/clientlayer', 'map/labelslayer',
         this.f = f;
       },
 
+      update: function () {
+        this.button.classList.toggle('active', this.active);
+      },
+
+      set: function (v) {
+        this.active = v;
+        this.update();
+      }
+    });
+
+    var LocateButton = ButtonBase.extend({
       onAdd: function () {
         var button = L.DomUtil.create('button', 'ion-locate shadow');
         button.setAttribute('data-tooltip', _.t('button.tracking'));
@@ -33,33 +44,12 @@ define(['map/clientlayer', 'map/labelslayer',
         return button;
       },
 
-      update: function () {
-        this.button.classList.toggle('active', this.active);
-      },
-
-      set: function (v) {
-        this.active = v;
-        this.update();
-      },
-
       onClick: function () {
         this.f(!this.active);
       }
     });
 
-    var CoordsPickerButton = L.Control.extend({
-      options: {
-        position: 'bottomright'
-      },
-
-      active: false,
-      button: undefined,
-
-      initialize: function (f, o) {
-        L.Util.setOptions(this, o);
-        this.f = f;
-      },
-
+    var CoordsPickerButton = ButtonBase.extend({
       onAdd: function () {
         var button = L.DomUtil.create('button', 'ion-pin shadow');
         button.setAttribute('data-tooltip', _.t('button.location'));
@@ -73,20 +63,10 @@ define(['map/clientlayer', 'map/labelslayer',
         return button;
       },
 
-      update: function () {
-        this.button.classList.toggle('active', this.active);
-      },
-
-      set: function (v) {
-        this.active = v;
-        this.update();
-      },
-
       onClick: function (e) {
         L.DomEvent.stopPropagation(e);
         this.f(!this.active);
       }
-
     });
 
     function mkMarker(dict, iconFunc, router) {
diff --git a/lib/map/clientlayer.js b/lib/map/clientlayer.js
index 1773b3f..a85f2e4 100644
--- a/lib/map/clientlayer.js
+++ b/lib/map/clientlayer.js
@@ -1,5 +1,5 @@
-define(['leaflet'],
-  function (L) {
+define(['leaflet', 'helper'],
+  function (L, helper) {
     'use strict';
 
     return L.TileLayer.Canvas.extend({
@@ -13,13 +13,6 @@ define(['leaflet'],
         this.redraw();
       },
       drawTile: function (canvas, tilePoint) {
-        function getTileBBox(s, map, tileSize, margin) {
-          var tl = map.unproject([s.x - margin, s.y - margin]);
-          var br = map.unproject([s.x + margin + tileSize, s.y + margin + tileSize]);
-
-          return [br.lat, tl.lng, tl.lat, br.lng];
-        }
-
         if (!this.data) {
           return;
         }
@@ -29,7 +22,7 @@ define(['leaflet'],
         var map = this._map;
 
         var margin = 50;
-        var bbox = getTileBBox(s, map, tileSize, margin);
+        var bbox = helper.getTileBBox(s, map, tileSize, margin);
 
         var nodes = this.data.search(bbox);
 
diff --git a/lib/map/labelslayer.js b/lib/map/labelslayer.js
index 2382522..910421a 100644
--- a/lib/map/labelslayer.js
+++ b/lib/map/labelslayer.js
@@ -1,5 +1,5 @@
-define(['leaflet', 'rbush'],
-  function (L, rbush) {
+define(['leaflet', 'rbush', 'helper'],
+  function (L, rbush, helper) {
     'use strict';
 
     var labelLocations = [['left', 'middle', 0 / 8],
@@ -188,13 +188,6 @@ define(['leaflet', 'rbush'],
         this.redraw();
       },
       drawTile: function (canvas, tilePoint, zoom) {
-        function getTileBBox(s, map, tileSize, margin) {
-          var tl = map.unproject([s.x - margin, s.y - margin]);
-          var br = map.unproject([s.x + margin + tileSize, s.y + margin + tileSize]);
-
-          return [br.lat, tl.lng, tl.lat, br.lng];
-        }
-
         if (!this.labels) {
           return;
         }
@@ -212,7 +205,7 @@ define(['leaflet', 'rbush'],
           return { p: p, label: d.label };
         }
 
-        var bbox = getTileBBox(s, map, tileSize, this.margin);
+        var bbox = helper.getTileBBox(s, map, tileSize, this.margin);
 
         var labels = this.labels.search(bbox).map(projectNodes);
 
diff --git a/lib/utils/helper.js b/lib/utils/helper.js
index b9fa5ed..7be6362 100644
--- a/lib/utils/helper.js
+++ b/lib/utils/helper.js
@@ -232,5 +232,11 @@ define({
     }
 
     return p;
+  },
+  getTileBBox: function getTileBBox(s, map, tileSize, margin) {
+    var tl = map.unproject([s.x - margin, s.y - margin]);
+    var br = map.unproject([s.x + margin + tileSize, s.y + margin + tileSize]);
+
+    return [br.lat, tl.lng, tl.lat, br.lng];
   }
 });