eccodes/definitions/grib1/section.2.def

# SECTION 2, Grid description section

# Length of section
position offsetSection2;
section_length[3] section2Length ;
meta section2Pointer section_pointer(offsetSection2,section2Length,2);
transient radius=6367470;
alias radiusOfTheEarth=radius;
alias radiusInMetres=radius;
transient shapeOfTheEarth=0: hidden; #ECC-811

# NV -- number of vertical coordinate parameters
unsigned[1] numberOfVerticalCoordinateValues : dump ;

constant neitherPresent = 255;

alias NV = numberOfVerticalCoordinateValues;
alias numberOfCoordinatesValues= numberOfVerticalCoordinateValues;

# PV -- location (octet number)
unsigned[1] pvlLocation = 255;

# Data representation type
codetable[1] dataRepresentationType 'grib1/6.table' = 0;
meta gridDefinitionDescription codetable_title(dataRepresentationType);

# Grid definition (according to data representation type - octet 6 above)
alias isRotatedGrid = false;

if (dataRepresentationType < 192) {
  template dataRepresentation "grib1/grid_definition_[dataRepresentationType:l].def";
} else {
  template dataRepresentation "grib1/grid_definition_[dataRepresentationType:l].[centre:l].def";
}
position endGridDefinition;

position offsetBeforePV;
transient PVPresent = ( NV > 0);

if (pvlLocation != neitherPresent) {
  padto padding_sec2_2(offsetSection2 + pvlLocation - 1);
} else {
  padto padding_sec2_2(offsetSection2 + 32 );
}

if (PVPresent ) {
  ibmfloat pv[NV] : dump;
  alias vertical.pv=pv;
}

position offsetBeforePL;

transient PLPresent = (section2Length > (offsetBeforePL - offsetSection2))
      && (section2Length >= (Nj * 2 + offsetBeforePL - offsetSection2));

if (PLPresent) {
  # For grib 1 -> 2
  constant numberOfOctectsForNumberOfPoints = 2;
  constant interpretationOfNumberOfPoints = 1;

  unsigned[2] pl[Nj] : dump;
  alias geography.pl=pl;
}

if (PVPresent == 0 && PLPresent == 0) {
  # pad to the end of the grid definiton as in documentation
  # ( gribex compatibility )
  padto padding_sec2_1(offsetSection2 + 32);
}

#when (PVPresent == 0)  {  set NV = 0;}
when ((PVPresent == 1) or (PLPresent==1)) {
  set pvlLocation = offsetBeforePV - offsetSection2 + 1;
}
when ((PVPresent == 0) and (PLPresent==0)) { set pvlLocation = 255; }

alias reducedGrid = PLPresent;

# GRIB-534: To easily remove vertical coordinates, set this key to 1
concept_nofail deletePV(unknown) {
   "1" = { PVPresent=0; NV=0; }
}

padtoeven padding_sec2_3(offsetSection2,section2Length);

meta md5Section2 md5(offsetSection2,section2Length);
alias md5GridSection = md5Section2;

constant isSpectral = !isGridded : constraint;