topic Datum Shift in ArcGIS Runtime SDK for WPF (Retired) Questions https://community.esri.com/t5/arcgis-runtime-sdk-for-wpf-retired-questions/datum-shift/m-p/323686#M1624 <HTML><HEAD></HEAD><BODY><SPAN>If I were to place a GPSLayer on top of a map that is projected in British National Grid, then I would need to address the issue that the GPS data (in WGS84) was using a different spatial reference from the map.</SPAN><BR /><BR /><SPAN>Looking at the GPSLayer Members, I can set a ProjectionService (e.g. to a local geometry service) in order to perform a behind-the-scenes projection.</SPAN><BR /><BR /><SPAN>My question is - will the ProjectionService also choose an appropriate GeoTransformation to apply (to transform from the WGS84 datum to the OSGB36 datum that underlies British National Grid)?</SPAN><BR /><BR /><SPAN>If it does, then how do I ascertain which transformation it is using? And if it doesn't, then I can expect to witness a datum shift, whereby the GPS will display in the wrong location - what can I do about this, short of writing my own GpsLayer?</SPAN></BODY></HTML> Fri, 03 May 2013 09:46:59 GMT DavidMartin 2013-05-03T09:46:59Z Datum Shift https://community.esri.com/t5/arcgis-runtime-sdk-for-wpf-retired-questions/datum-shift/m-p/323686#M1624 <HTML><HEAD></HEAD><BODY><SPAN>If I were to place a GPSLayer on top of a map that is projected in British National Grid, then I would need to address the issue that the GPS data (in WGS84) was using a different spatial reference from the map.</SPAN><BR /><BR /><SPAN>Looking at the GPSLayer Members, I can set a ProjectionService (e.g. to a local geometry service) in order to perform a behind-the-scenes projection.</SPAN><BR /><BR /><SPAN>My question is - will the ProjectionService also choose an appropriate GeoTransformation to apply (to transform from the WGS84 datum to the OSGB36 datum that underlies British National Grid)?</SPAN><BR /><BR /><SPAN>If it does, then how do I ascertain which transformation it is using? And if it doesn't, then I can expect to witness a datum shift, whereby the GPS will display in the wrong location - what can I do about this, short of writing my own GpsLayer?</SPAN></BODY></HTML> Fri, 03 May 2013 09:46:59 GMT https://community.esri.com/t5/arcgis-runtime-sdk-for-wpf-retired-questions/datum-shift/m-p/323686#M1624 DavidMartin 2013-05-03T09:46:59Z