I am trying to perform a reprojection for data with datum Nad27 to WGS84 datum. According to AndreJ in some previous questions in Stackexchange (CRS reprojection for instance) QGIS uses internally by default the ntv2 transformation from NAD27 to WGS84, that should be very exact. I tested with the custom crs calculation tool. First a lat lon point at 99w , 19n with parameters for EPSG32614 looks like this:
The same point (which is near Mexico City) with EPSG 26714 parameters looks like this:
There is a difference of 126 meters on the north coordinate but no difference in the east coordinate which is odd. I tested a custom crs I created with a towgs84 argument as follows:
Now I have a difference for both the east and north coordinate that should be expected for the datum change. Adding the same towgs84 to EPSG 26714 makes no difference with figure 2
Making the reprojection of the same coordinates in GPS Babel gives me that the point in UTM NAD27 is 500032mE, 2,100,627mN. There is almost no difference with my custom crs. So I wonder how to make the correctly the reprojection of the data.
Thanks before hand