   Specifications of MMF_MOD format.
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   MMF_EPO format is for distribution the model of the mean mapping function 
   (MMF) in the neutral atmosphere

   A file in MMF_MOD format consists of records of variable length
   in ASCII coding. The records are separated by a character with decimal
   code 13. The records are grouped into sections. Sections follow
   in this order:

1) Header record -- the first record should have a signature:
                    # MMF_MOD   Format of 2008.09.21

                    The header record allows to distinguish a valid
                    file in the MMF_MOD format from files
                    in other formats.

2) M-record section
   The M record defines the model identifier.

3) N-record section
   N record defines the number of stations, the minimum and maximum
   elevation angle for which the mean mapping is build.  

4) S-record section
   S-record  defines a name and coordinates of each site. 
   A site cannot be defined more than once.

5) D-record section
   D-record coefficients of the mean mapping function for a given station,
   given component of the model, given variable

6) Trailer record -- the last record is the same as the header record.



Format of an N-record:
----------------------

Field   1:1   A1    -- Record ID. Should be letter N (decimal code 78).
field   2:9   a8       delimiter: blanks.
Field  10:13  I4    -- The number of stations
field  14:15  a2       delimiter: blanks.
Field  16:23  F8.5  -- The minimum elevation in degrees.
field  14:15  a2       delimiter: blanks.
Field  26:33  F8.5  -- The minimum elevation in degrees.


Format of an S-record:
----------------------

Field  1:1   A1    -- Record ID. Should be letter S (decimal code 83).
field  2:2   a1       delimiter: blanks.
Field  4:11  A8    -- 8-letter long site identifier. May contain
                      any characters with decimal codes 32-255, but
                      blanks are allowed only at the end of the site
                      identifier. This site identifier should be unique
                      among S-records. This field should not
                      necessarily have a special meaning. Parsing
                      software should not try to interpret it.
field 12:13  a2       delimiter: blanks.
Field 14:26  F13.4 -- X site coordinate in a crust fixed reference
                      frame. Units: meters.
field 27:27  a1       delimiter: blank.
Field 28:40  F13.4 -- Y site coordinate in a crust fixed reference
                      frame. Units: meters.
field 27:27  a1       delimiter: blank.
Field 42:54  F13.4 -- Z site coordinate in a crust fixed reference
                      frame. Units: meters.
field 55:56  a2       delimiter: blanks.
Field 57:64  F8.4  -- Site geocentric latitude, positive to north,
                      in degrees. This field is for information only.
                      Parsing software MUST ignore it.
field 65:65  a1       delimiter: blank.
Field 66:73  F8.4  -- Site longitude, positive towards east,
                      in degrees. This field is for information only.
                      Parsing software MUST ignore it.
field 74:74  a1       delimiter: blank.
Field 75:80  F6.1  -- Site height above the reference ellipsoid in
                      meters. This field is for information only.
                      Parsing software MUST ignore it.

Format of an D-record:
----------------------

Field    1:1   A1      -- Record ID. Should be letter D (decimal code 6  8).
field    2:2   a1         delimiter: blanks.
Field    4:11  A8      -- 8-letter long site identifier. 
field   12:13  a2         delimiter: blanks.
Field   14:16  A3      -- model component:
                          HYD -- hydrostatic component
                          NHY -- non-hydrostatic component
field   17:18  a2         delimiter: blanks.
Field   19:26  A8      -- Model variable
                          DER_NORT -- Tilt of the symmetry axis in the north direction
                          DER_EAST -- Tilt of the symmetry axis in the east  direction
                          CHEB_0   -- 0-th degree Chebyshev polynomial coefficient for the mapping function perturbation
                          CHEB_1   -- 1-st degree Chebyshev polynomial coefficient for the mapping function perturbation
                          CHEB_2   -- 2-nd degree Chebyshev polynomial coefficient for the mapping function perturbation
                          CHEB_3   -- 3-rd degree Chebyshev polynomial coefficient for the mapping function perturbation
                          CHEB_4   -- 4-th degree Chebyshev polynomial coefficient for the mapping function perturbation
                          CHEB_5   -- 5-th degree Chebyshev polynomial coefficient for the mapping function perturbation
field   27:28  a2         delimiter: blanks.
Field   29:39  1PD11.4 -- Average coefficient for a given variable.
field   40:41  a2         delimiter: blanks.
Field   42:52  A8      -- Cosine amplitude for the annual variation of a given variable.
field   53:54  a2         delimiter: blanks.
Field   55:65  A8      -- Sine amplitude for the annual variation of a given variable.
field   66:67  a2         delimiter: blanks.
Field   68:78  A8      -- Cosine amplitude for the semi-annual variation of a given variable.
field   79:80  a2         delimiter: blanks.
Field   81:91  A8      -- Sine amplitude for the semi-annual variation of a given variable.
field   92:93  a2         delimiter: blanks.
Field   94:104 A8      -- Cosine amplitude for the ter-annual variation of a given variable.
field  105:106 a2         delimiter: blanks.
Field  107:117 A8      -- Sine amplitude for the ter-annual variation of a given variable.
field  118:119 a2         delimiter: blanks.
Field  120:130 A8      -- Cosine amplitude for the diurnal variation of a given variable.
field  131:132 a2         delimiter: blanks.
Field  133:143 A8      -- Sine amplitude for the diurnal variation of a given variable.

