Section 4 - Product definition section



Octet No.	Contents
1-4	Length of section in octets (nn)
5	Number of section (4)
6-7	Number of coordinates values after Template (see Note 1, below)
8-9	Product Definition Template Number (see Code Table 4.0)
10-xx	Product Definition Template (see Template 4.X, where X is the Product Definition Template Number given in octets 8-9)
[xx+1]-nn	Optional list of coordinates values (see Notes 2 and 3, below)


Notes:

(1) Coordinates values are intended to document the vertical discretisation associated with model data on hybrid coordinate vertical levels. A number of zero in octets 6-7 indicates that no such values are present. Otherwise the number corresponds to the whole set of values.

(2) Hybrid systems, in the context, employ a means of representing vertical coordinates in terms of a mathematical combination of pressure and sigma coordinates. When used in conjunction witha surface pressure field and an appropriate mathematical expression, the vertical coordinate parameters may be used to interpret the hybrid vertical coordinate.

(3) Hybrid coordinate values, if present, should be encoded in IEEE 32-bit floating point format. They are inteded to be encoded as pairs.