Element KSEC1(24) is set to 1 if an ECMWF local use definition is required or has been found in a GRIB message; element KSEC1(37) indicates which definition it is.
If KSEC1(24) is set to 0, no local use definition is present in the message.
Currently, the following definitions exist:
| Octet | KSEC1 element | Comments |
|---|---|---|
| 1-3 | - | Length of section 1 |
| 4 | 1 | Version number of code table 2 |
| 5 | 2 | Identification of centre (ECMWF = 98) |
| 6 | 3 | Generating process identification number |
| 7 | 4 | Grid definition |
| 8 | 5 | Section 2/3 indication flag |
| 9 | 6 | Parameter indicator |
| 10 | 7 | Level indicator/satellite identifier |
| 11 | 8 | Height/pressure of level |
| 12 | 9 | Height/pressure of level |
| 13 | 10 | Year |
| 14 | 11 | Month |
| 15 | 12 | Day |
| 16 | 13 | Hour |
| 17 | 14 | Minute |
| 18 | 15 | Time unit indicator |
| 19 | 16 | Time period |
| 20 | 17 | Time period |
| 21 | 18 | Time range indicator |
| 22-23 | 19 | Number of products in an average |
| 24 | 20 | Number of products missing from an average |
| 25 | 21 | Century |
| 26 | 22 | Sub-centre identifier |
| 27-28 | 23 | Decimal scale factor |
| - | 24 | Flag to indicate local usage in section 1 |
| 29-40 | 25-36 | Zero |
| 41 | 37 | ECMWF local GRIB usage definition identifier* |
| 42 | 38 | Class |
| 43 | 39 | Type |
| 44-45 | 40 | Stream |
| 46-49 | 41 | Version number or experiment identifier |
* Local definition numbers 192 to 255 inclusive will never be used to define ECMWF local extensions to section 1, GRIB code. They are free to be defined and used by Member States.