Single file, multiple level format
The data that nm can read

Structure: (may repeat for multiple Level 0 records)

- Comment lines beginning with '#'

- the top-level (Level 0) parameter names, each followed by '= value'

these parameters are those which change most slowly in the dataset

- followed by a record of bottom-level (Level 1) parameter names

- finally, the data records.

Rules:

- Data columns may be space delimited, comma delimited, or tab delimited.

- Missing or bad data is indicated by any variation of -9, or by 'nd'.

# Basic Hydrographic Data
# from Carl Wunsch
#
sta = 6,  lat =  38.03,  lon = -72.99

  press  temp      sal     o2    sigth 
  5.000  16.942  33.097   6.020  24.069
 25.000  15.268  35.001   6.320  25.915
 49.000  10.605  34.557   5.820  26.503
 99.000  12.133  35.508   5.180  26.961
149.000  -9.000  35.581   5.120  27.037
199.000  11.474  35.523   4.620  27.101

sta = 7,  lat =  37.93,  lon = -72.69

  press  temp      sal     o2    sigth 
  5.000  17.697  33.787   5.760  24.419
 25.000  15.268  35.001   6.320  25.915
 49.000  14.548  35.298   5.620  26.302
 99.000  12.162  35.426   4.710  26.892
149.000  12.229  35.592   4.360  27.010
199.000  11.027  35.416   4.440  27.100
300.000   8.478  35.119   3.600  27.300

sta = 8,  lat = 37.78    lon = -72.43

...(and so on)...