function salinity = pss1978(cond,temp,pres)

%  pss1978 -- Salinity from 1978 Practical Salinity Scale. 
%      Calculate salinity from conductivity, temperature, and
%      pressure using the 1978 Practical Salinity Scale
%      (IEEE Journal of Ocean Engineering, Vol. OE-5, No. 1,
%      January 1980, page 14.).
%
%      cond is conductivity in mmho/cm (a factor of 10 greater
%         greater than conductivity in Siemens/meter).
%      temp is temperature in degrees Celsius.
%      pres is pressure in dbars relative to the sea surface.
%      salinity is in practical salinity units, which are often
%         considered the same as ppt.
% 
%      Fran Hotchkiss, December 19, 1997.

%  Use Seabird standard for Ro = Cond (35 ppt,  15 deg Cel,  0 dbar).
Ro = 42.914;
A =  [3.989e-15    -6.370e-10    2.070e-5];
B1 =  3.426e-2;
B2 =  4.464e-4;
B3 =  4.215e-1;
B4 = -3.107e-3;
a = [ 2.7081    -7.0261    14.0941     25.3851     -0.1692     0.0080];
b = [-0.0144     0.0636    -0.0375     -0.0066     -0.0056     0.0005];
c = [ 1.0031e-9    -6.9698e-7    1.104259e-4    2.00564e-2   6.766097e-1];
k = 0.0162;

R = cond ./ Ro;
rT = polyval(c,temp);
RPnum = pres .* polyval(A,pres);
RPden = 1 + B1*temp + B2.*temp.*temp + B3*R + B4.*R.*temp;
RP = 1 + RPnum ./ RPden;
RT = R ./ (RP .* rT);
rootRT = sqrt(RT);
tfac = (temp - 15) ./ (1 + k .* (temp - 15));
salinity = polyval(a,rootRT) + tfac .* polyval(b,rootRT);