Phase V of the migration process deals with the changes necessary to introduce use of the new geodetic datum (CIGD11) and the new geoid models for the Sister Islands. CBGM0811 in Cayman Brac and LCGM0811 in Little Cayman. This phase does not include any changes for Grand Cayman.
What will change in Phase V (February 2013):
- The two new CORS in the Sister Islands CBMD and LCSB will begin transmission of correction signals reflecting their CIGD11 positions i.e. as at midnight on the morning of Jan 1st 2011 relative to the International Terrestrial Reference Frame 2005 - ITRF05(2011.0).
- A new transformation, CIGD11-SIGD61-EPSG, will be required to convert from the new ITRF05(2011.0) positions to the existing local geodetic datum (SIGD61). This will replace the existing transformation (NAD83(CORS96)-SIGD61). CIGD11-SIGD61-EPSG is a temporary transformation which will no longer be needed once the final phase introducing the new national grid (CING11) is complete.
- Site calibrations which convert from the old NAD83 reference frame to site easting, northing will need to be re-calculated (not re-observed), if they are to be used with the new datum.
What will not change in Phase V:
- The easting northing values of all CORS and all control stations will not change at this stage.
- The existing Transverse Mercator projection will still be used to convert from the existing local geodetic datum (SIGD61) to the existing national grid (SING61).
- Phase V does not affect Grand Cayman.