These parameter values are taken from NZGD49 to NZGD2000 (1) (code 1566) and assume that NZGD2000 and WGS 84 are coincident to within the accuracy of the tfm. For better accuracy use NZGD49 to WGS 84 (2) (code 1564) or NZGD49 to WGS 84 (3) (code 1670).