## GRIB2 - SECTION 3
GRID DEFINITION SECTION

Created 05/10/05

Octet No. | Content
--- | ---
1-4 | 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)
7-10 | Number of data points
11 | Number of octets for optional list of numbers defining number of points (See note 2 below)
12 | Interpolation of list of numbers defining number of points (See Table 3.11)
13-14 | Grid definition template number (= N) (See Table 3.1)
15-xx | Grid definition template (See Template 3.N, where N is the grid definition template number given in octets 13-14)
[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 15-xx (15-nn 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 quasi-regular 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 ans 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 Nj or Ny 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 defining the number of points corresponds to either the coordinate lines as given in the grid definition, or to a full circle.

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