topic Re: How to read the current scale of a Map? in ArcGIS API for Silverlight Questions

How to read the current scale of a Map?

SuiHuang — Tue, 19 Apr 2011 16:55:32 GMT

Hi Everybody:

    I am writing a Silverlight program that reads a ArcGIS Server 10 map service feature layer (such as http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Network/USA/MapServer/80).
    When this layer is displayed on the map I want to find a method to read the current display scale, because I want to zoom out to make sure the scale number is larger than "Min. Scale" of the map service, and then I can check whether the map is displayed when the scale is out of the range defined by "Min. Scale" and "Max. Scale".
    However, I haven't found the method to get the exact number. The Scalebar control give a good scale legend, but not the exact number to compare with "Min. Scale" of the map service. In the Map control I haven't found a property to return that value neither.
    Any idea how I can get the nubmer?
    Thank you.

My development environment:
-- .NET 4
-- C# and Visual Studio 2010
-- Silverlight 4
-- ESRI ArcGIS API for Microsoft Silverlight/WPF
-- ArcGIS server 10.01 map services

Re: How to read the current scale of a Map?

JenniferNery — Tue, 19 Apr 2011 20:19:54 GMT

The ScaleBar has a ScaleValue property: http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.ScaleBar~ScaleValue.html which is calculated based on the Map.Resolution.

Re: How to read the current scale of a Map?

SuiHuang — Wed, 20 Apr 2011 20:07:33 GMT

Thank you jenniferdnery! I will try.

The ScaleBar has a ScaleValue property: http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.ScaleBar~ScaleValue.html which is calculated based on the Map.Resolution.

Re: How to read the current scale of a Map?

vipulsoni — Thu, 21 Apr 2011 06:15:43 GMT

Thank you jenniferdnery! I will try.

Take this code.. might help you.

#region getMapScale
        /// <summary>
        /// getMapScale
        /// </summary>
        /// <param name="esriMap"></param>
        /// <returns></returns>
        public double getMapScale(Map esriMap)
        {
            double dpi = 96; //screen resolution: pixels per inch
            double screenUnitsPerMapUnit = 39.37; //inches per meter
            double mapResolution = esriMap.Resolution;
            double scale = (dpi * screenUnitsPerMapUnit * mapResolution);
            return scale;
        }
        #endregion

#region MAP SCALE CHANGE
        /// <summary>
        /// MAP SCALE CHANGED
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Map_ExtentChanged(object sender, ExtentEventArgs e)
        {
            double Map_Scale = getMapScale(Map);

            int scaled = Convert.ToInt32(Math.Round(Map_Scale));

            MapScale.Text = "1 : " + scaled;
        }
        #endregion