[Qgis-user] NTV2 Grid Shits

[stevejking]

Tyler,
 NAD27 and ATS77 don't seem to share the same ellipsoid.
spatialreference.org lists ATS77 as 
+proj=sterea +lat_0=47.25 +lon_0=-63 +k=0.999912 +x_0=700000 +y_0=400000
+a=6378135 +b=6356750.304921594 +units=m +no_defs 

It's missing a +towgs84= or +nadgrids= BUT Notice the ellipsoid a and b
parameters do not match the NAD27 clarke66 ellipsoid. So a nadgrids shift
file for NAD27, will not work for ATS77.

Steve



--
Sent from: http://osgeo-org.1560.x6.nabble.com/QGIS-User-f4125267.html