topic transformation between WGS 84 Web Mercator / WGS84 Web Mercator (Auxiliary Sphere) and WGS 84 (ellipsoid) in Coordinate Reference Systems Questions https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791565#M572 <HTML><HEAD></HEAD><BODY><P>Team,</P><P></P><P>You may already read the articles on WGS 84 Web Mercator / WGS84 Web Mercator (Auxiliary Sphere) and WGS 84 (ellipsoid). For example,</P><P></P><OL><LI><A href="https://alastaira.wordpress.com/2011/01/23/the-google-maps-bing-maps-spherical-mercator-projection/" title="https://alastaira.wordpress.com/2011/01/23/the-google-maps-bing-maps-spherical-mercator-projection/">The Google Maps / Bing Maps Spherical Mercator Projection | Alastair Aitchison</A></LI><LI><A href="http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-and-areas-when-your-map-uses-the-mercator-projection/" title="http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-and-areas-when-your-map-uses-the-mercator-projection/">http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-and-areas-when-your-map-uses-the-mercator-projection/</A></LI></OL><P></P><P>In practice, how do you deal with the datum/projection transformation between WGS 84 Web Mercator / WGS84 Web Sphere Mercator&nbsp; and WGS 84 (ellipsoid). Also, how to transfer major local datum /projection like WKID 102204 (Ain_el_Abd_1970_Aramco_Lambert_2 ) into WGS 84 Web Mercator / WGS84 Web Sphere Mercator&nbsp; 'properly'?</P><P></P><P>Any advice?</P></BODY></HTML> Sun, 17 May 2015 07:26:44 GMT larryzhang 2015-05-17T07:26:44Z transformation between WGS 84 Web Mercator / WGS84 Web Mercator (Auxiliary Sphere) and WGS 84 (ellipsoid) https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791565#M572 <HTML><HEAD></HEAD><BODY><P>Team,</P><P></P><P>You may already read the articles on WGS 84 Web Mercator / WGS84 Web Mercator (Auxiliary Sphere) and WGS 84 (ellipsoid). For example,</P><P></P><OL><LI><A href="https://alastaira.wordpress.com/2011/01/23/the-google-maps-bing-maps-spherical-mercator-projection/" title="https://alastaira.wordpress.com/2011/01/23/the-google-maps-bing-maps-spherical-mercator-projection/">The Google Maps / Bing Maps Spherical Mercator Projection | Alastair Aitchison</A></LI><LI><A href="http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-and-areas-when-your-map-uses-the-mercator-projection/" title="http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-and-areas-when-your-map-uses-the-mercator-projection/">http://blogs.esri.com/esri/arcgis/2010/03/05/measuring-distances-and-areas-when-your-map-uses-the-mercator-projection/</A></LI></OL><P></P><P>In practice, how do you deal with the datum/projection transformation between WGS 84 Web Mercator / WGS84 Web Sphere Mercator&nbsp; and WGS 84 (ellipsoid). Also, how to transfer major local datum /projection like WKID 102204 (Ain_el_Abd_1970_Aramco_Lambert_2 ) into WGS 84 Web Mercator / WGS84 Web Sphere Mercator&nbsp; 'properly'?</P><P></P><P>Any advice?</P></BODY></HTML> Sun, 17 May 2015 07:26:44 GMT https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791565#M572 larryzhang 2015-05-17T07:26:44Z Re: transformation between WGS 84 Web Mercator / WGS84 Web Mercator (Auxiliary Sphere) and WGS 84 (ellipsoid) https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791566#M573 <HTML><HEAD></HEAD><BODY><P>If you're using EPSG:3857 / ESRI: 102100 / OpenLayers:900913, you don't need to do anything different than converting to the regular old EPSG:4326, WGS 1984. The funky WGS 1984 "sphere" conversion is done in the projection algorithm, rather than via a geographic/datum transformation. You would just need to pick or define a transformation to convert from Ain el Abd 1970 to WGS 1984.</P><P></P><P>If you're using Esri:102113 or EPSG:3785 (why??), those do use a sphere-based GeoCRS and you had to do some sort of bookkeeping transformation to convert between then. However, no actual coordinate change takes place.</P><P></P><P>Melita</P></BODY></HTML> Mon, 18 May 2015 19:41:07 GMT https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791566#M573 MelitaKennedy 2015-05-18T19:41:07Z Re: transformation between WGS 84 Web Mercator / WGS84 Web Mercator (Auxiliary Sphere) and WGS 84 (ellipsoid) https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791567#M574 <HTML><HEAD></HEAD><BODY><P>Thx, Melita,</P><P>...</P><P>The funky WGS 1984 "sphere" conversion is done in the projection algorithm, rather than via a geographic/datum transformation.</P><P>...</P><P></P><P>It looks that some offsets exist, in the North part of the Middle East Peninsula, if no transformation applied.</P><P></P><P>Your info gives some hints, which may trigger me to try something else.</P><P></P><P>+++++++++++++</P><P></P><P>For EPSG 3785, one of the reasons that our customers accept 'was' as follows:</P><P></P><H1>EPSG:3785</H1><P>Popular Visualisation CRS / Mercator</P><P style="font-size: 0.8em;"></P><UL><LI>WGS84 Bounds: -180.0000, -85.0000, 180.0000, 85.0000&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </LI><LI>Projected Bounds: -20037508.3428, -19971868.8804, 20037508.3428, 19971868.8804</LI><LI>Scope: <STRONG>Certain Web mapping and visualisation applications</STRONG>.</LI><LI>Last Revised: March 14, 2008</LI><LI>Area: World - 85°S to 85°N</LI></UL></BODY></HTML> Tue, 19 May 2015 04:21:05 GMT https://community.esri.com/t5/coordinate-reference-systems-questions/transformation-between-wgs-84-web-mercator-wgs84/m-p/791567#M574 larryzhang 2015-05-19T04:21:05Z