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specifies a UNIX filename containing a bitmap definition in the format defined in appendix 1 of the  Dissemination manual.

The bitmap specification is that defined for dissemination purposes in appendix 3 of ECMWF Meteorological Bulletin M3.1: "The dissemination of ECMWF products to Member States", D.Jokic. revision 3 9/97.

The a bitmap definition as described below. The specification is an ASCII text description of a rectangular area bitmap; the specification is held in a Unix file. The bitmap specification takes the form of a set of command-like definitions containing the following:

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END, a stand-alone directive ending the specification.

For example:

The following example illustrates the use of the directives above. First the dissemination requirements:

DIS,COUNTRY=EC,TYPE=FC,LEVT=PL,LEVE=500,STEP=240,FORM=GRIB,PARA=GH,REPR=LL,GRID=0.5/0.5,AREA=4.5/0.0/0.0/4.5,
BITMAP=”ECM_001.BITMAP”

The bitmap specification is contained in a separate file, ECM_001.BITMAP, in the same directory as the file containing the dissemination requirements. It contains the following:

SPEC,SIZE=10:10,VALUES=OFF,
POINTS=01:03-08/10,
       03:02-04/07-09,
       04:02/03/08/09,
       06:0,
       07:01-03/08-10,
       09:01-10
END

Givesand gives the following bitmap:

    0 0 1 1 1 1 1 1 0 1
    0 0 1 1 1 1 1 1 0 1
    0 1 1 1 0 0 1 1 1 0
    0 1 1 0 0 0 0 1 1 0
    0 1 1 0 0 0 0 1 1 0
    0 0 0 0 0 0 0 0 0 0
    1 1 1 0 0 0 0 1 1 1
    1 1 1 0 0 0 0 1 1 1
    1 1 1 1 1 1 1 1 1 1
    1 1 1 1 1 1 1 1 1 1

Notes:

1. Within POINTS, values for rows remain defined until new values are given. Thus, in the example above:
   
   • row 2 is the same as row 1
   • row 5 is the same as row 4
   • row 8 is the same as row 7
   • row 10 is the same as row 9
2. The definition of row 6 simply indicates that no points are to be switched from the preset value defined in VALUES.
3. If VALUES=ON had been coded, the values in the bitmap would all be reversed, thus:

    1 1 0 0 0 0 0 0 1 0 
    1 1 0 0 0 0 0 0 1 0 
    1 0 0 0 1 1 0 0 0 1 
    1 0 0 1 1 1 1 0 0 1 
    1 0 0 1 1 1 1 0 0 1 
    1 1 1 1 1 1 1 1 1 1 
    0 0 0 1 1 1 1 0 0 0 
    0 0 0 1 1 1 1 0 0 0 
    0 0 0 0 0 0 0 0 0 0 
    0 0 0 0 0 0 0 0 0 0

4. Member States may define a number of bitmaps in this way; it is suggested that, at least initially, this number be kept below about 20.
5. The same bitmap may be used for different areas, provided the areas conform with one another (i.e. have the same number of rows and columns).