As it is known to many people, Google Maps is the Mercator coordinates system. But we more commonly used is WGS84 coordinate system, this type of coordinates suitable for overlay vector electronic map , GPS coordinates positioning , GPS navigation and GPS logistics monitoring or other filed. Here we download a small Bing Satellite Map, then use ArcGIS transfer into WGS84, and explain how to convert the maps of Mercator coordinate system to WGS84 coordinate system in ArcGIS. In order to make the effect of projection transformation more obvious and more easier to understand the difference between Mercator coordinate system and WGS84 coordinate system, we download Maps Downloader For Bing Satellite the satellite map coordinates accurately without offset. We take global level 3 as the sample data. In all types of maps , only Bing and Google satellite map satellite map coordinates are accurate. You can select any regions you like. Double-click the left mouse button in the box , and will show ' New Task ' dialog box in the lower left corner of the dialog box, we will set the coordinate to ' -180 , -85 ,' the top right corner coordinates is set to ' 180,85 ' ( in Mercator coordinate system the latitude coordinates can only get to plus or minus 85 degrees ) , we select only the level at level 3 , as shown below. After the download completely, you will be asked whether you want to export the image data , select 'Yes' , the ' Select Task ' dialog box in which we select only the task we have just downloaded 'Global Bing satellite maps ' and 'Global Bing satellite map _ Hybrid ', as shown below. Click the ' OK' button, display the 'Export Image Data' dialog box , the default level is automatically downloaded to our level , ' Level 3 ' Export Type select ' Mosaic: To one image ', choose 'GeoTIFF (*. TIF)' format as saving type( this format can help us make projection conversion ). Click the ' Output' button, respectively, to generate ' Global Bing Satellite Map-Hybrid ' file and the 'Global Bing satellite map” , the former name information , the latter is a pure satellite map. Start ArcMap software, which is commonly used version 9.3,10.0,10.1 version ( until now has 10.2 version ) , here we take 5.0 for example. Select 'Data Management Tools ->, Projections and Transformations ->, Raster ->, Project Raster”，in the displayed ArcToolbox dialog box. Click on 'Input Raster' area open folder icon to display the 'Input Raster' dialog box , in the dialog box , choose our downloaded 'Global Bing satellite map' files ( Do not double-click) then click 'Add' button. After select the data source , it will display the file path in 'Input Raster' ( in fact, we can directly enter the file path ) , and we set the path to save the output files in 'Output Raster Dataset' area ( here plus the file extension tif). Click the ' OK' button to complete the setting , then select the drop-down list contents 'Geographic Transformation' area. Click 'OK' button to start the projection transformation , then wait a moment, the bottom right corner of the software window will pop up a message window to complete the conversion . That’s the whole process, you can download Maps Downloader For Bing Satellite (http://www.arceyessoft.com/download/sgbs.zip)for a free trial. Google uses a geographic coordinate system of decimal longitude,latitude. As does MapPoint, although Google assumes a spherical Earth (spherical geoid) whilst MapPoint uses the more-correct WGS84 (the same as NAVSTAR and most GPS receivers). Projections are the transformations from a spherical Earth (eg. geographic coordinates) to a flat sheet of paper (eg. x,y coordinates). Google and MapPoint do use different projections but they only control how the map looks on the screen - to plot on both maps, you will use geographic coordinates regardless of the projection. Source.