Grids are defined in GRIB2 using an accuracy of 1/1000000 (one millionth) of a degree. If this accuracy is not sufficient to describe your grid (latitude/longitude of first and last points, as well as grid increments) without loss of information, you can use a GRIB2 feature that provides a way to describe any regular grid.

Explanation of i/j coordinates and how they are used to describe the encoded fields in GRIB 2 (and ecCodes):

Example of the most used GRIB 2 encoding

Scanning mode 0

  • iScansPositively (west to east)
    • i points are consecutive
  • jScansNegatively (north to south)


GRIB 2 Code Figues


GRIB
Number of points along a parallel

Number of points along a meridian

Basic angle of the initial production domain

Subdivisions of basic angle

Latitude of first grid point
(°)
Latitude of last grid point
(°)
Longitude of first grid point
(°)
Longitude of last grid point
(°)
i direction increment
(°)
j direction increment
(°)
Resolution and component flags
()
Scanning Mode
()