Simplify scaleline calculation

src/ol/control/scalelinecontrol.js

@@ -8,14 +8,10 @@ goog.require('goog.events');
 goog.require('goog.style');
 goog.require('ol');
 goog.require('ol.Object');
-goog.require('ol.TransformFunction');
 goog.require('ol.control.Control');
 goog.require('ol.css');
-goog.require('ol.math');
-goog.require('ol.proj');
 goog.require('ol.proj.METERS_PER_UNIT');
 goog.require('ol.proj.Units');
-goog.require('ol.sphere.NORMAL');
 
 
 /**
@@ -106,12 +102,6 @@ ol.control.ScaleLine = function(opt_options) {
    */
   this.renderedHTML_ = '';
 
-  /**
-   * @private
-   * @type {?ol.TransformFunction}
-   */
-  this.toEPSG4326_ = null;
-
   var render = options.render ? options.render : ol.control.ScaleLine.render;
 
   goog.base(this, {
@@ -203,61 +193,21 @@ ol.control.ScaleLine.prototype.updateElement_ = function() {
 
   var center = viewState.center;
   var projection = viewState.projection;
+  var metersPerUnit = projection.getMetersPerUnit();
   var pointResolution =
-      projection.getPointResolution(viewState.resolution, center);
+      projection.getPointResolution(viewState.resolution, center) *
-  var projectionUnits = projection.getUnits();
+      metersPerUnit;
-
-  var cosLatitude;
-  var units = this.getUnits();
-  if (projectionUnits == ol.proj.Units.DEGREES &&
-      (units == ol.control.ScaleLineUnits.METRIC ||
-       units == ol.control.ScaleLineUnits.IMPERIAL ||
-       units == ol.control.ScaleLineUnits.US ||
-       units == ol.control.ScaleLineUnits.NAUTICAL)) {
-
-    // Convert pointResolution from degrees to meters
-    this.toEPSG4326_ = null;
-    cosLatitude = Math.cos(ol.math.toRadians(center[1]));
-    pointResolution *= Math.PI * cosLatitude * ol.sphere.NORMAL.radius / 180;
-    projectionUnits = ol.proj.Units.METERS;
-
-  } else if (projectionUnits != ol.proj.Units.DEGREES &&
-      units == ol.control.ScaleLineUnits.DEGREES) {
-
-    // Convert pointResolution from other units to degrees
-    if (!this.toEPSG4326_) {
-      this.toEPSG4326_ = ol.proj.getTransformFromProjections(
-          projection, ol.proj.get('EPSG:4326'));
-    }
-    cosLatitude = Math.cos(ol.math.toRadians(this.toEPSG4326_(center)[1]));
-    var radius = ol.sphere.NORMAL.radius;
-    goog.asserts.assert(ol.proj.METERS_PER_UNIT[projectionUnits],
-        'Meters per unit should be defined for the projection unit');
-    radius /= ol.proj.METERS_PER_UNIT[projectionUnits];
-    pointResolution *= 180 / (Math.PI * cosLatitude * radius);
-    projectionUnits = ol.proj.Units.DEGREES;
-
-  } else {
-    this.toEPSG4326_ = null;
-  }
-
-  goog.asserts.assert(
-      ((units == ol.control.ScaleLineUnits.METRIC ||
-        units == ol.control.ScaleLineUnits.IMPERIAL ||
-        units == ol.control.ScaleLineUnits.US ||
-        units == ol.control.ScaleLineUnits.NAUTICAL) &&
-       projectionUnits == ol.proj.Units.METERS) ||
-      (units == ol.control.ScaleLineUnits.DEGREES &&
-       projectionUnits == ol.proj.Units.DEGREES),
-      'Scale line units and projection units should match');
 
   var nominalCount = this.minWidth_ * pointResolution;
   var suffix = '';
+  var units = this.getUnits();
   if (units == ol.control.ScaleLineUnits.DEGREES) {
-    if (nominalCount < 1 / 60) {
+    var metersPerDegree = ol.proj.METERS_PER_UNIT[ol.proj.Units.DEGREES];
+    pointResolution /= metersPerDegree;
+    if (nominalCount < metersPerDegree / 60) {
       suffix = '\u2033'; // seconds
       pointResolution *= 3600;
-    } else if (nominalCount < 1) {
+    } else if (nominalCount < metersPerDegree) {
       suffix = '\u2032'; // minutes
       pointResolution *= 60;
     } else {