Phase I of the migration process deals with the changes necessary to introduce use of the new geodetic datum (CIGD11) in Grand Cayman and the new geoid model for Grand Cayman (GCGM0811). This phase does not include any of the planned changes for the Sister Islands.

What will change in Phase I (July 2010):

• The geodetic coordinates (latitude, longitude, ellipsoid height) of both the Grand Cayman CORS (GCGT and GCFS) will change. The receivers will not move, but the geodetic coordinates stored on the receiver and transmitted as part of the correction signal will change to reflect their positions on Jan 1st 2011 relative to the International Terrestrial Reference Frame 2005 (ITRF05).
   
• A new transformation, GCGD11-GCGD59, will be required to convert from the new ITRF05(2011.0) positions to the existing local geodetic datum (GCGD59). This will replace the existing transformation (GC7P). (The new transformation CIGD11-GCGD59 is adapted from GC7P - their respective accuracies being almost identical. This 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.

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What will not change in Phase I:

• 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 (GCGD59) to the existing national grid (GCNG59).
   
• Phase I does not affect the Sister Islands. The Sister Islands will be addressed in future phases after the installation of a new CORS on Little Cayman and the repositioning of the current Cayman Brac CORS (CBSB).

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Overview of Phase I Workflow Changes