ExGrib.Grib2.Section5.Templates.GridPointDataSimplePackingWithLogarithmPreProcessing (ex_grib v0.0.1) View Source

Template 5.61

Grid point data simple packing with logarithm pre processingng

Notes:

(1) The template is approriately designed for data sets with all non-negative values and a wide variability range (more then 5 orders of magnitude). It must not be used for data sets with negative values or smaller variability range.

(2) A logarithm pre-processing algorithm is used to fit the variability range into one or two order of magnitudes before using the simple packing algorithm. It requires a parameter (B) to assure that all values passed to the logarithm function are positive.Thus scaled values are Z=ln (Y+B), where Y are the original values, ln is the natural logarithm (or Napierian) function and B is chosen so that Y+B>0.

(3) Best pratice follows for choosing the B pre-processing parameter.   (a) If the data set minimum value is positive, B can be safely put to zero.   (b) If the data set minimum is zero, all values must be scaled to become greater than

zero and B can be equal to the minimum positive value in the data set.

(4) Data shall be packed using Data template 7.

https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_temp5-61.shtml

Link to this section Summary

Link to this section Functions