GRIB2 - GRID DEFINITION TEMPLATE 3.0

Latitude/Longitude (or equidistant
cylindrical, or Plate Carree)

Revised 01/07/2013
Red text depicts changes made since 11/05/2007



Octet No. Contents
15 Shape of the Earth (See Code Table 3.2)
16 Scale Factor of radius of spherical Earth
17-20 Scale value of radius of spherical Earth
21 Scale factor of major axis of oblate spheroid Earth
22-25 Scaled value of major axis of oblate spheroid Earth
26 Scale factor of minor axis of oblate spheroid Earth
27-30 Scaled value of minor axis of oblate spheroid Earth
31-34 Ni—number of points along a parallel     
35-38 Nj—number of points along a meridian
39-42 Basic angle of the initial production domain (see Note 1)
43-46 Subdivisions of basic angle used to define extreme longitudes and latitudes, and direction increments (see Note 1)
47-50 La1—latitude of first grid point (see Note 1)
51-54 Lo1—longitude of first grid point (see Note 1)
55 Resolution and component flags (see Flag Table 3.3)
56-59 La2—latitude of last grid point (see Note 1)
60-63 Lo2—longitude of last grid point (see Note 1)
64-67 Di—i direction increment (see Notes 1 and 5)
68-71 Dj—j direction increment (see Note 1 and 5)
72 Scanning mode (flags — see Flag Table 3.4)
73-nn

List of number of points along each meridian or parallel
(These octets are only present for quasi-regular grids as described in notes 2 and 3)



Notes:

1.  Basic angle of the initial production domain and subdivisions of this basic angle are provided to manage cases where the recommended unit of 10-6 degrees is not applicable to describe the extreme longitudes and latitudes, and direction increments. For these last six descriptors, the unit is equal to the ratio of the basic angle and the subdivisions number. For ordinary cases, zero and missing values should be coded, equivalent to respective values of 1 and 10 (10-6  degrees unit).

2.  For data on a quasi-regular grid, in which all the rows or columns do not necessarily have the same number of grid points either Ni (octets 31-34) of Nj (octets 35-38) and the corresponding Di (octets 64-67) or Dj (octets 68-71) shall be coded with all bits set to 1 (missing). The actual number of points along each parallel or meridian shall be coded in the octets immediately following the grid definition template (octets [xx+1]-nn), as described in the description of the grid definition section.

3.  A quasi-regular grid is only defined for appropriate grid scanning modes. Either rows or columns, but not both simultaneously, may have variable numbers of points or variable spacing. The first point in each row (column) shall be positioned at the meridian (parallel) indicted by octets 47-54. The grid points shall be evenly spaced in latitude (longitude).

4.  A scale value of radius of spherical Earth, or major axis of oblate spheroid Earth is delivered from applying appropriate scale factor to the value expressed in meters.

5.  It is recommended to use unsigned direction increments.



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