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function DEPTHM = sw_dpth(P,LAT) |
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% SW_DPTH Depth from pressure |
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%=========================================================================== |
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% SW_DPTH $Id: sw_dpth.m,v 1.1 2003/12/12 04:23:22 pen078 Exp $ |
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% Copyright (C) CSIRO, Phil Morgan 1992. |
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% |
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% USAGE: dpth = sw_dpth(P,LAT) |
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% |
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% DESCRIPTION: |
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% Calculates depth in metres from pressure in dbars. |
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% |
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% INPUT: (all must have same dimensions) |
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% P = Pressure [db] |
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% LAT = Latitude in decimal degress north [-90..+90] |
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% (lat may have dimensions 1x1 or 1xn where P(mxn). |
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% |
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% OUTPUT: |
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% dpth = depth [metres] |
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% |
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% AUTHOR: Phil Morgan 92-04-06 (morgan@ml.csiro.au) |
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% |
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% DISCLAIMER: |
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% This software is provided "as is" without warranty of any kind. |
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% See the file sw_copy.m for conditions of use and licence. |
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% |
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% REFERENCES: |
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% Unesco 1983. Algorithms for computation of fundamental properties of |
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% seawater, 1983. _Unesco Tech. Pap. in Mar. Sci._, No. 44, 53 pp. |
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%========================================================================= |
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% Modifications |
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% 99-06-25. Lindsay Pender, Fixed transpose of row vectors. |
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% CALLER: general purpose |
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% CALLEE: none |
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%------------- |
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% CHECK INPUTS |
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%------------- |
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[mP,nP] = size(P); |
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[mL,nL] = size(LAT); |
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if mL==1 & nL==1 % LAT scalar - fill to size of P |
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LAT = LAT*ones(size(P)); |
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elseif nP == nL & mL == 1 % LAT is row vector |
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LAT = LAT(ones(1, mP), :); % Coppy down each column |
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elseif mP == mL & nL == 1 % LAT is column vector |
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LAT = LAT(:, ones(1, nP)); % Copy across each row |
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elseif mP == mL & nP == nL |
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% Ok |
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else |
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error('sw_depth.m: Inputs arguments have wrong dimensions') |
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end %if |
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%------------- |
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% BEGIN |
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%------------- |
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% Eqn 25, p26. Unesco 1983. |
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DEG2RAD = pi/180; |
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c1 = +9.72659; |
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c2 = -2.2512E-5; |
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c3 = +2.279E-10; |
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c4 = -1.82E-15; |
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gam_dash = 2.184e-6; |
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LAT = abs(LAT); |
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X = sin(LAT*DEG2RAD); % convert to radians |
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X = X.*X; |
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bot_line = 9.780318*(1.0+(5.2788E-3+2.36E-5*X).*X) + gam_dash*0.5*P; |
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top_line = (((c4*P+c3).*P+c2).*P+c1).*P; |
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DEPTHM = top_line./bot_line; |
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return |
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%=========================================================================== |
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% |
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