Packing 4: Spherical harmonics complex packing
| Octets | Key | Type | Content |
| 12-13 | N | ||
| 14-15 | IP (where IP = int (1000 x P)) | ||
| 16 | J1 | ||
| 17 | K1 | ||
| 18 | M1 | ||
| 19 | Binary data . Unpacked binary data represented in 004 octets in the same way as the reference value . (pairs of coefficients) . N Packed binary data | ||
| ... | Unpacked binary data represented in 004 octets in the same way as the reference value (pairs of coefficients) | ||
| N | Packed binary data |
( 1) Removal of the real (0.0) coefficient considerably reduces the variability of the coefficients and results in better packing.
( 2) For some spherical harmonic representations, the (0.0) coefficient represents the mean value of the parameter represented.
( 3) For spherical harmonics complex packing, J1, K1, M1 are the pentagonal resolution parameters specifying the truncation of a subset of the data, which shall be represented unpacked (as is the reference value) and shall precede the packed data.
P defines a scaling factor by which is packed not the field itself, but the modulus of .2P of the field, where .2 is the Laplacian operator. Thus the coefficients fmn will be multiplied by (n(n+1))P before packing, and divided by this factor after unpacking.
N is a pointer to the start of the packed data (i.e. gives octet number)
(J1, K1, M1 > 0 and P 0, + or -)
The representation mode (Code figure = 2 in Code table 10) in Section 2 shall indicate this type of packing, but as Section 2 is optional, the flag field in Section 4 may also be used to indicate the more complex method.