Octet Number  Content 


Length of the section in octets (nn) 
5 
Number of the section (3) 
6 
Source of grid definition (See Table 3.0) (See note 1 below) 
710 
Number of data points 
11 
Number of octets for optional list of numbers defining number
of points (See note 2 below) 
12 
Interpetation of list of numbers
defining number of points (See Table
3.11) 
1314 
Grid definition template number
(= N) (See Table 3.1) 
15xx 
Grid definition template (See
Template 3.N, where N is the grid definition template number given in octets 1314) 
[xx+1]nn 
Optional list of numbers
defining number of points (See notes 2, 3, and 4 below) 
Notes: 1. If octet 6 is not zero, octets 15xx (15nn if octet 11 is zero) may not be supplied. This should be documented with all bits set to 1 in the grid definition template number. 2. An optional list of numbers defining number of points is used to document a quasiregular grid, where the number of points may vary from one row to another. In such a case, octet 11 is non zero and gives the number octets on which each number of points is encoded. For all other cases, such as regular grids, octets 11 and 12 are zero and no list is appended to the grid definition template. 3. If a list of numbers defining the number of points is preset, it is appended at the end of the grid definition template ( or directly after the grid definition number if the template is missing). When the grid definition template is present, the length is given according to bit 3 of the scanning mode flag octet (length is N_{j} or N_{y} for flag value 0). List ordering is implied by data scanning. 4. Depending on the code value given in octet 12, the list of numbers either:  Corresponds to the coordinate lines as given in the grid definition, or  Corresponds to a full circle, or  Does not apply. 