Creating TAB with custom CRS using QGIS?

Question

I meet problem about reproject in Qgis.

I created coordinate user defined. i used version Qgis 2.2. I defined coordinate:

Name: VN 2000 / 107.75 3degees

Parameters:

+proj=tmerc +lat_0=0 +lon_0=107.75 +k=0.9999 +x_0=500000 +y_0=0 +ellps=WGS84 +towgs84=-191.90441429,-39.30318279,-111.45032835,-0.00928836,0.01975479,-0.00427372,0.252906278 +units=m +no_defs

1. when i save as (.shp format) new file to coordinate i create in here. It gets full parameters.

2. But when i save Mapinfo (.tab) format. It doesn't get full parameters (it's missing towgs84):

And if i open file in mapinfo software and overlay in Google earth, coordinate is not correct because it doesn't get 7 parameters (towgs84).

Can you help me? why it get full parameters?

Answer 1

Software that does not rely on GDAL/PROJ (like QGIS does) handles datum shifts separately from the projection. This is useful when several datum shifts exist for a specific projection.

If you can not define a custom datum with the mapinfo software, reproject your data to a CRS based on the WGS84 ellipsoid inside QGIS. Or create a second custom CRS with towgs84 parameters all zero, and reproject your data from one to the other.