Section 2 - Grid description section

      Octet
      No.
      Contents
      1-3Length of section (octets)
      4NV -- number of vertical coordinate parameters
      5PV -- location (octet number) of the list of vertical coordinate parameters, if present; or
      PL -- location (octet number) of the list of numbers of points in each row (if no vertical coordinate parameters are present), if present; or
      255 (all bits set to 1) if neither are present
      6Data representation type (see Code table 6)
      7-32Grid definition (according to data representation type - octet 6 above)
      33-42Extensions of grid definition for rotation or stretching of the coordinate system or Lambert conformal projection or Mercator projection
      33-44Extensions of grid definition for space view perspective projection
      33-52Extensions of grid definition for stretched and rotated coordinate system
      PVList of vertical coordinate parameters (length = NV x 4 octets); if present, then PL = 4NV + PV
      PLList of numbers of points in each row (length = NROWS x 2 octets, where NROWS is the total number of rows defined within the grid description)




      NOTES:

      1. Vertical coordinate parameters are used in association with hybrid vertical coordinate systems.

      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 with a surface pressure field and an appropriate mathematical expression, the vertical coordinate parameters may be used to interpret the hybrid vertical coordinate.

      3. Each vertical coordinate parameter is represented in 4 octets, using the scheme for representing floating point numbers described in the Regulations.



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