% Function TRUEW.M
% Converted from C true wind computation code truewind.c .
% Created: 12/17/96
% Comments updated: 10/01/97
% Developed by: Shawn R. Smith and Mark A. Bourassa
% Programmed by: Mylene Remigio
% Last updated: 9/30/2014
% Direct questions to: wocemet@coaps.fsu.edu
%
% 9/30/2014 : If the true wind has speed and its coming from the north
% then its direction should be 360deg. The problem was fixed
% in which the programs’s output showed 0deg instead of 360deg.
%
% This routine will compute meteorological true winds (direction from
% which wind is blowing, relative to true north; and speed relative to
% the fixed earth).
%
% INPUT VALUES:
%
% num integer Number of observations in input (crse, cspd,
% wdir, wspd, hd) and output (adir, tdir, tspd)
% data arrays. ALL ARRAYS MUST BE OF EQUAL LENGTH.
% sel integer Sets option for diagnostic output. There are
% four settings:
%
% Option 4: Calculates true winds from input
% arrays with no diagnostic output or
% warnings. NOT RECOMMENDED.
% Option 3: [DEFAULT] Diagnostic output lists the
% array index and corresponding
% variables that either violate the
% range checks or are equal to the
% missing value. An additional table
% lists the number of observation times
% with no missing values, some (but not
% all) missing values, and all missing
% values; as well as similar totals for
% the observation times that fail the
% range checks. Range checks identify
% negative input values and verify
% directions to be between 0 and 360
% degrees.
% Option 2: In addition to the default
% diagnostics (option 3), a table of
% all input and output values for
% observation times with missing data
% is provided.
% Option 1: Full diagnostics -- In addition to
% the diagnostics provided by option 2
% and 3, a complete data chart is
% output. The table contains input and
% output values for all observation
% times passed to truewind.
%
% crse real array Course TOWARD WHICH the vessel is moving over
% the ground. Referenced to true north and the
% fixed earth.
% cspd real array Speed of vessel over the ground. Referenced
% to the fixed earth.
% hd real array Heading toward which bow of vessel is pointing.
% Referenced to true north.
% zlr real Zero line reference -- angle between bow and
% zero line on anemometer. Direction is clockwise
% from the bow. (Use bow=0 degrees as default
% when reference not known.)
% wdir real array Wind direction measured by anemometer,
% referenced to the ship.
% wspd real array Wind speed measured by anemometer,referenced to
% the vessel's frame of reference.
% wmis real array Five element array containing missing values for
% crse, cspd, wdir, wspd, and hd. In the output,
% the missing value for tdir is identical to the
% missing value specified in wmis for wdir.
% Similarly, tspd uses the missing value assigned
% to wmis for wspd.
% *** WDIR MUST BE METEOROLOGICAL (DIRECTION FROM)! CRSE AND CSPD MUST
% BE RELATIVE TO A FIXED EARTH! ***
% OUTPUT VALUES:
% tdir real array True wind direction - referenced to true north
% and the fixed earth with a direction from which
% the wind is blowing (meteorological).
% tspd real array True wind speed - referenced to the fixed earth.
% adir real array Apparent wind direction (direction measured by
% wind vane, relative to true north). IS
% REFERENCED TO TRUE NORTH & IS DIRECTION FROM
% WHICH THE WIND IS BLOWING. Apparent wind
% direction is the sum of the ship relative wind
% direction (measured by wind vane relative to the
% bow), the ship's heading, and the zero-line
% reference angle. NOTE: The apparent wind speed
% has a magnitude equal to the wind speed measured
% by the anemometer.
% DIAGNOSTIC OUTPUT:
% nw integer Number of observation times for which tdir and
% tspd were calculated (without missing values)
% nwpm integer Number of observation times with some values
% (crse, cspd, wdir, wspd, hd) missing. tdir,
% tspd set to missing value.
% nwam integer Number of observation times with all values
% (crse, cspd, wdir, wspd, hd) missing. tdir,
% tspd set to missing value.
% nwf integer Number of observation times where the program
% fails -- at least one of the values (crse, cspd,
% wdir, wspd, hd) is invalid
%************************************************************************
function truew(num, sel, crse, cspd, wdir, zlr, hd, adir, wspd, ...
wmis, tdir, tspd, nw, nwam, nwpm, nwf)
% INITIALIZE VARIABLES
x = 0;
y = 0;
nw = 0;
nwam = 0;
nwpm = 0;
nwf = 0;
dtor = pi/180; %degrees to radians conversion
% LOOP OVER 'NUM' VALUES
i = 1;
while( i <= num)
% CHECK COURSE, SHIP SPEED, HEADING, WIND DIRECTION, AND WIND
% SPEED FOR VALID VALUES (i.e. neither missing nor outside
% physically acceptable ranges).
if( ( ((crse(i) < 0) || (crse(i)> 360)) && (crse(i) ~= wmis(1)) ) || ...
( (cspd(i) < 0) && (cspd(i) ~= wmis(2)) )|| ...
( ((wdir(i) < 0) || (wdir(i) > 360)) && (wdir(i) ~= wmis(3)) ) || ...
( (wspd(i) < 0) && (wspd(i) ~= wmis(4)) ) || ...
( ((hd(i) < 0) || (hd(i) > 360)) && (hd(i) ~= wmis(5)) ) )
% WHEN SOME OR ALL OF INPUT DATA FAILS RANGE CHECK, TRUE WINDS ARE SET
% TO MISSING. STEP INDEX FOR INPUT VALUE(S) BEING OUT OF RANGE
nwf = nwf + 1;
tdir(i) = wmis(3);
tspd(i) = wmis(4);
if( (crse(i) ~= wmis(1)) && (cspd(i) ~= wmis(2)) && ...
(wdir(i) ~= wmis(3)) && (wspd(i) ~= wmis(4)) && ...
(hd(i) ~= wmis(5)) )
% STEP INDEX FOR ALL INPUT VALUES BEING NON-MISSING
nw = nw + 1;
else
if( (crse(i) ~= wmis(1)) || (cspd(i) ~= wmis(2)) || ...
(wdir(i) ~= wmis(3)) || (wspd(i) ~= wmis(4)) || ...
(hd(i) ~= wmis(5)) )
% STEP INDEX FOR PART OF INPUT VALUES BEING MISSING
nwpm = nwpm + 1;
else
% STEP INDEX FOR ALL INPUT VALUES BEING MISSING
nwam = nwam + 1;
end
end
% WHEN COURSE, SHIP SPEED, HEADING, WIND DIRECTION, AND WIND
% SPEED ARE ALL IN RANGE AND NON-MISSING, THEN COMPUTE TRUE WINDS.
elseif( (crse(i) ~= wmis(1)) && (cspd(i) ~= wmis(2)) && ...
(wdir(i) ~= wmis(3)) && (wspd(i) ~= wmis(4)) && ...
(hd(i) ~= wmis(5)) )
nw = nw + 1;
% CONVERT FROM NAVIGATIONAL COORDINATES TO ANGLES COMMONLY USED
% IN MATHEMATICS
mcrse = 90 - crse(i);
% KEEP THE VALUE BETWEEN 0 AND 360 DEGREES
if( mcrse <= 0.0 )
mcrse = mcrse + 360.0;
end
% CHECK ZLR FOR VALID VALUE. IF NOT VALID, SET EQUAL TO ZERO.
if( (zlr < 0.0) || (zlr > 360.0) )
zlr = 0.0;
end
% CALCULATE APPARENT WIND DIRECTION
adir(i) = hd(i) + wdir(i) + zlr;
% KEEP ADIR BETWEEN 0 AND 360 DEGREES
while( adir(i) >= 360.0 )
adir(i) = adir(i) - 360.0;
end
% CONVERT FROM METEOROLOGICAL COORDINATES TO ANGLES COMMONLY USED
% IN MATHEMATICS
mwdir = 270.0 - adir(i);
% KEEP MDIR BETWEEN 0 AND 360 DEGREES
if( mwdir <= 0.0 )
mwdir = mwdir + 360.0;
end
if( mwdir > 360.0 )
mwdir = mwdir - 360.0;
end
% DETERMINED THE EAST-WEST VECTOR COMPONENT AND THE NORTH-SOUTH
% VECTOR COMPONENT OF THE TRUE WIND
x = (wspd(i) .* cos(mwdir .* dtor)) + (cspd(i) .* cos(mcrse .* dtor));
y = ((wspd(i) .* sin(mwdir .* dtor)) + (cspd(i) .* sin(mcrse .* dtor)));
% USE THE TWO VECTOR COMPONENTS TO CALCULATE THE TRUE WIND SPEED
tspd(i) = sqrt((x .* x) + (y .* y));
calm_flag = 1;
% DETERMINE THE ANGLE FOR THE TRUE WIND
if(abs(x) > 0.00001)
mtdir = (atan2(y,x)) / dtor;
else
if(abs(y) > 0.00001)
mtdir = 180.0 - (90.0 * y) / abs(y);
else
% THE TRUE WIND SPEED IS ESSENTIALLY ZERO: WINDS ARE CALM
% AND DIRECTION IS NOT WELL DEFINED
mtdir = 270.0;
calm_flag = 0;
end
end
% CONVERT FROM THE COMMON MATHEMATICAL ANGLE COORDINATE TO THE
% METEOROLOGICAL WIND DIRECTION
tdir(i) = 270.0 - mtdir;
% MAKE SURE THAT THE TRUE WIND ANGLE IS BETWEEN 0 AND 360 DEGREES
while(tdir(i) < 0.0)
tdir(i) = (tdir(i) + 360.0) .* calm_flag;
end
while(tdir(i) > 360.0)
tdir(i) = (tdir(i) - 360.0) .* calm_flag;
end
% ENSURE WMO CONVENTION FOR TDIR=360 FOR WIN FROM NORTH AND TSPD > 0
if (calm_flag == 1 && (tdir(i) < 0.0001))
tdir(i) = 360.0;
end
x = 0.0;
y = 0.0;
else
if( (crse(i) ~= wmis(1)) || (cspd(i) ~= wmis(2)) || ...
(wdir(i) ~= wmis(3)) || (wspd(i) ~= wmis(4)) || ...
(hd(i) ~= wmis(5)) )
nwpm = nwpm + 1;
tdir(i) = wmis(3);
tspd(i) = wmis(4);
% WHEN COURSE, SHIP SPEED, APPARENT DIRECTION, AND WIND SPEED
% ARE ALL IN RANGE BUT ALL OF THESE INPUT VALUES ARE MISSING,
% THEN SET TRUE WIND DIRECTION AND SPEED TO MISSING.
else
nwam = nwam + 1;
tdir(i) = wmis(3);
tspd(i) = wmis(4);
end
end
% INCREASE COUNTER
i = i + 1;
end
% OUTPUT SELCTION PROCESS
switch(sel)
case 1
full(num, crse, cspd, wdir, zlr, hd, adir, wspd, tdir, tspd), ...
missing_values(num, crse, cspd, wdir, hd, wspd, tdir, tspd, wmis), ...
truerr(num, crse, cspd, hd, wdir, wspd, wmis, nw, nwpm, nwam, nwf);
case 2
missing_values(num, crse, cspd, wdir, hd, wspd, tdir, tspd, wmis), ...
truerr(num, crse, cspd, hd, wdir, wspd, wmis, nw, nwpm, nwam, nwf);
case 3
truerr(num, crse, cspd, hd, wdir, wspd, wmis, nw, nwpm, nwam, nwf);
otherwise
fprintf('Selection not valid. Using selection #3 by default. \n'), ...
truerr(num, crse, cspd, hd, wdir, wspd, wmis, nw, nwpm, nwam, nwf);
end
end
% **********************************************************************
% OUTPUT SUBROUTINES
% **********************************************************************
% Function: FULL
% Purpose: Produces a complete data table with all values.
% Accessed only when selection #1 is chosen.
function full(num, crse, cspd, wdir, zlr, hd, adir, wspd, tdir, tspd)
fprintf('------------------------------------------------------------------------------------\n');
fprintf('\n FULL TABLE\n');
fprintf(' ************\n');
fprintf(' index course sspeed windir zeroln shiphd | appspd | appdir trudir truspd\n')
for j = 1:num
fprintf('%7d %7.1f %7.1f %7.1f %7.1f %7.1f | %7.1f | %7.1f %7.1f %7.1f\n', ...
(j),crse(j),cspd(j),wdir(j),zlr,hd(j),wspd(j),adir(j),tdir(j),tspd(j));
end
fprintf('\n NOTE: Wind speed measured by anemometer is identical\n');
fprintf(' to apparent wind speed (appspd).\n');
fprintf('\n------------------------------------------------------------------------------------\n');
end
% **********************************************************************
% Function: MISSING_VALUES
% Purpose: Produces a data table of the data with missing values.
% Accessed when selection #1 or #2 is chosen.
function missing_values(num, crse, cspd, wdir, hd, wspd, tdir, tspd, wmis)
fprintf('\n MISSING DATA TABLE\n');
fprintf(' ********************\n');
fprintf(' index course sspeed windir shiphd appspd trudir truspd\n');
for j = 1:num
if( (crse(j) ~= wmis(1)) && (cspd(j) ~= wmis(2)) && ...
(wdir(j) ~= wmis(3)) && (wspd(j) ~= wmis(4)) && ...
(hd(j) ~= wmis(5)) )
continue;
else
fprintf(' %7d %7.1f %7.1f %7.1f %7.1f %7.1f %7.1f %7.1f\n', ...
(j), crse(j), cspd(j), wdir(j), hd(j), wspd(j), tdir(j), tspd(j));
end
end
fprintf('\n------------------------------------------------------------------------------------\n');
end
% **********************************************************************
% Function: TRUERR
% Purpose: List of where range tests fail and where values are
% invalid. Also prints out number of records which are
% complete, incomplete partially, incomplete entirely, and
% where range tests fail. Accessed when selection #1, #2,
% #3, or the default is chosen.
function truerr(num, crse, cspd, hd, wdir, wspd, wmis, nw, nwpm, nwam, nwf)
fprintf('\n TRUEWINDS ERRORS\n');
fprintf(' ******************\n');
for i=1:num
if( ((crse(i) < 0) || (crse(i) > 360)) && (crse(i) ~= wmis(1)) )
fprintf(' Truewinds range test failed. Course value #%d invalid.\n',(i));
end
if( (cspd(i) < 0) && (cspd(i) ~= wmis(2)) )
fprintf(' Truewinds range test failed. Vessel speed value #%d invalid.\n',(i));
end
if( ((wdir(i) < 0) || (wdir(i) > 360)) && (wdir(i) ~= wmis(3)) )
fprintf(' Truewinds range test failed. Wind direction value #%d invalid.\n',(i));
end
if( (wspd(i) < 0) && (wspd(i) ~= wmis(4)) )
fprintf(' Truewinds range test failed. Wind speed value #%d invalid.\n',(i));
end
if( ((hd(i) < 0) || (hd(i) > 360)) && (hd(i) ~= wmis(5)) )
fprintf(' Truewinds range test failed. Ship heading value #%d invalid.\n',(i));
end
end
fprintf('\n');
for i =1:num
if(crse(i) == wmis(1))
fprintf(' Truewinds data test: Course value #%d missing.\n', (i));
end
if(cspd(i) == wmis(2))
fprintf(' Truewinds data test: Vessel speed value #%d missing.\n', (i));
end
if(wdir(i) == wmis(3))
fprintf(' Truewinds data test: Wind direction value #%d missing.\n', (i));
end
if(wspd(i) == wmis(4))
fprintf(' Truewinds data test: Wind speed value #%d missing.\n', (i));
end
if(hd(i) == wmis(5))
fprintf(' Truewinds data test: Ship heading value #%d missing.\n', (i));
end
end
fprintf('\n------------------------------------------------------------------------------------\n');
fprintf('\n DATA REVIEW\n');
fprintf(' *************\n');
fprintf(' no data missing = %4d\n', nw);
fprintf(' part of data missing = %4d\n', nwpm);
fprintf(' all data missing = %4d\n', nwam);
fprintf(' failed range tests = %4d\n', nwf);
end