function sofie_uncertainties,pat

;- Read the SOFIE uncertainty file:  'sofie_uncertainties.txt', 
;  which currently contains total errors (random + systematic).
;  The input variable 'pat' is the location of this file.
   
   file = pat + '/sofie_uncertainties.txt'
   
   openr,lu,file,/get_lun
   
   head = ' '
   for i = 1,4 do readf,lu,head
   
   d = fltarr(8,11)
   readf,lu,d
   
   close,lu & free_lun,lu
   
;- return a structure
   
   s = create_struct($
   'z',   reform( d(0,*) ), $  ; altitude scale
   't',   reform( d(1,*) ), $  ; T uncertainty (K), same for sunrise & sunset
   'co2', reform( d(2,*) ), $  ; CO2 uncertainty (%)     "
   'h2o', reform( d(3,*) ), $  ; H2O uncertainty (%)       "
   'o3',  reform( d(4,*) ), $  ; O3 uncertainty (%)        "
   'ch4', reform( d(5,*) ), $  ; CH4 uncertainty (%)        "
   'no_r', reform( d(6,*) ), $ ; sunrise NO uncertainty (%)
   'no_s', reform( d(7,*) ) )  ; sunset NO uncertainty (%)

   return,s
   end