Calculating depth in the TMbottle data

    The depth values in these TMbottle files have been calculated from
pressure by the US JGOFS Data Management Office using the algorithm
below.  The latitude used in the computation was the beginning latitude 
recorded in the TMbottle file.  The CHECKVALUE was used to verify the 
accuracy of the computation.  The stated accuracy of this algorithm 
is 0.1 meters.  The calculated depths have been rounded to the 
nearest whole meter.




 function DEPTH=depth(P,LAT);

  DEPTH   Computes depth given the pressure at some latitude
          D=DEPTH(P,LAT) gives the depth D (m) for a pressure P
              (dbars) at some latitude LAT (degrees).

          Fofonoff and Millard (1982). UNESCO Tech Paper #44.

  Notes:  (ETP3, MBARI)
          This algorithm was originally compiled by RP @ WHOI.
          It was copied from the UNESCO technical report.
          The algorithm was endorsed by SCOR Working Group 51.
          The equations were originally developed by Saunders
              and Fofonoff (1976).  DSR 23: 109-111.
          The parameters were re-fit for the 1980 equation of
              state for seawater (EOS80).

  CHECKVALUE: D=9712.653 M FOR P=10000 DECIBARS, LAT=30 DEG

  CALCULATON ASSUMES STD OCEAN: T = 0 DEG C; S = 35 (IPSS-78)


  X = sin(LAT/57.29578);
  X' = X*X;


  GR = GRAVITY VARIATION WITH LAT: ANON (1970) BULLETIN GEODESIQUE

  GR = 9.780318*(1.0+(5.2788E-3+2.36E-5*X')*X') + 1.092E-6*P


  D = DEPTH BEFORE GRAVITY CORRECTION

  D = (((-1.82E-15*P+2.279E-10)*P-2.2512E-5)*P+9.72659)*P

  DEPTH = D/GR
  

  
  Pressure calculated from nominal depth:
  
  For three events added by the DMO to R/V Nathaniel B. Palmer 
  (AESOPS/NBP-97-3) Ross Sea Process Cruise 3, pressure was calculated 
  from the nominal depth (depth_n).  These events, added by the DMO to 
  facilitate the production of merged data products during the US JGOFS
  synthesis phase, were omitted from the data originally submitted to 
  the DMO.
  
  
  PRESSURE Computes pressure given the depth at some latitude
           P=PRESSURE(D,LAT) gives the pressure P (dbars) at a depth D (m)
           at some latitude LAT (degrees).
 
           Ref: Saunders, "Practical Conversion of Pressure to Depth",
               J. Phys. Oceanog., April 1981.
  

  Notes:  RP (WHOI) 2/Dec/91
          I copied this directly from the UNESCO algorithms.


  CHECK VALUE: P80=7500.004 DBARS;FOR LAT=30 DEG., DEPTH=7321.45 METERS

      PLAT=abs(XLAT*pi/180.)
      D=sin(PLAT)
      C1=5.92E-3+(D^2)*5.25E-3
      P80=((1-C1)-sqrt(((1-C1)^2)-(8.84E-6*DPTH)))/4.42E-6