This is what the tool grib_get_data provides: A list of latitude-longitude-value triplets for a GRIB message. Note that you can also use the API to access this functionality: See examples.
This is also called a geo iterator (as opposed to the keys iterator)

This iterator is only for grid-point data: For example it does not make sense for spherical harmonic coefficients.

Also it is not implemented for all grid types. At the time of writing only the following are supported:

  • Regular latitude/longitude
  • Rotated latitude/longitude
  • Regular Gaussian
  • Reduced latitude/longitude
  • Reduced Gaussian
  • Lambert conformal
  • Lambert azimuthal equal area
  • Polar stereographic
  • Mercator
  • Space view

If the iterator is not implemented for an input field, grib_get_data prints just the data values (without the latitude/longitudes).

The full list of grid types are listed here: GRIB edition 1 and GRIB edition 2.

There are also some useful keys which use this iterator:

  • latitudes: An array with all the latitudes of the grid points
  • longitudes: An array with all the longitudes of the grid points
  • latLonValues: An array with all the latitudes/longitudes/values for each point of the grid
    e.g. (lat1,lon1,value1, lat2,lon2,value2,..., latN,lonN,valueN)
    The length of this array is 3 times the length of the previous two.