g_rect.m 16.3 KB
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function g_rect
%G_RECT - Main function for georectifying oblique images.
%
% Syntax:  Simply type g_rect at the command line and follow the
%          instructions.
%
% Inputs:
%    The function G_RECT reads an input parameter file that contains all
%     information required to perfrorm a georectification of a given image.
%     The format of this parameter file is detailed on-line on the G_RECT
%     Wiki page.
%
% Outputs:
%    The function G_RECT creates an output file that contains the following
%    variables:
%
%        imgFname:      The reference image for the georectification.
%
%        firstImgFname: The first image of a sequence of images to which the
%                       georectification could be applied to. This is really
%                       just a comment.
%
%        lastImgFname: The last image of a sequence of images to which the
%                      georectification could be applied to. This is really
%                      just a comment.
%
%        frameRef:     The reference frame used. It could be either
%                      'Geodetic' or 'Cartesian'.
%
%        LON:          The main matrix that contain either the longitude of each
%                      pixel of the reference image (imgFname) or the x-coordinate
%                      (in m) depending on whether the package is used in geodetic or
%                      cartesian coordinates. 
%
%        LAT:          Same as LON but for the latitude or y-position.
%
%        LON0:         A scalar for the longitude or x-position of the camera.
%
%        LAT0:         Same as LON0 but for the latitude.
%
%        lon0_gcp:     A vector containing the longitude or x-position of each 
%                      ground control points (GCP). 
%
%        lat0_gcp:     Same as lon_gcp for latitude or y-position.
%
%        lon_gcp:      A vector containing the longitude or x-position of each 
%                      ground control points (GCP) projected onto the water level
%                      i.e. at 0 m of elevation. 
%
%        lat_gcp:      Same as lon_gcp for latitude or y-position.
%
%        h_gcp:        The elevation (in m) of the GCPs. The elevation is
%                      0 m if taken at water level.
%
%        i_gcp:        The horizontal index of the image ground control
%                      points.
%
%        j_gcp:        The vertical index of the image ground control
%                      points.
%
%        hfov:         The camera horizontal field of view [degree].
%
%        phi:          Camera tilt angle [degree].
%
%        lambda:       Camera dip angle [degree].
%
%        H:            The camera altitude relative to the water [m].
%
%        theta:        View angle clockwise from North [degree].
%
%        errGeoFit:    The rms error of the georectified image after
%                      geometrical transformation [m].
%
%        errPolyFit:   The rms error of the georectified image after
%                      geometrical transformation and the polynomial
%                      correction [m].
%
%        precision:    Calculation can be done in single or double
%                      precisions as defined by the user in the parameter
%                      file. With today's computers this is now obsolete
%                      and calculations can always be done in double
%                      precision.
%
%         Delta:       The effective resolution (im m) of the georectified image.
%
% Other m-files required: The m_map package.

% Subfunctions: all functions contained within the subdirectories g_rect/src/
%
% Author: Daniel Bourgault
%         Institut des sciences de la mer de Rimouski
%         email: daniel_bourgault@uqar.ca
%         Initial development: February 2013
%         Important update: May 2020

%%
% The minimization is repeated nMinimize times where each time a random
% combination of the initial guesses is chosen within the given
% uncertainties provided by the user. This is becasue the algorithm often
% converges toward a local minimum. The repetition is used to increase chances
% that the minimum found is a true minimum within the uncertainties provided.
nMinimize = 50;

%% Read the parameter file
% Count the number of header lines before the ground control points (GCPs)
% The GCPs start right after the variable gcpData is set to true.
display('  ');
display('  Welcome to g_rect: a package for georectifying oblique images on a flat ocean');
display('  Authors: Daniel Bourgault and Rich Pawlowicz');
display('  ');
inputFname = input('  Enter the filename for the input parameters: ','s');
fid = fopen(inputFname);

nHeaderLine  = 0;
gcpData      = false;

% Read and execute each line of the parameter file until gcpData = true
% after which the GCP data appear and are read below with the 'importdata'
% function.
while gcpData == false
    eval(fgetl(fid));
    nHeaderLine = nHeaderLine + 1;
end
fclose(fid);

% The older version of the code had a variable called 'field' that could be
% set to 'true' or 'false' in the input parameters file depending on whether 
% the application was done for a field situation (field = true) or a lab 
% situation (field = false). It was implicitly assumed that positions were 
% given by a geodetic system (lon-lat) for field situations and by a 
% cartesian system (x-y) for lab situations. But this was a little confusing 
% as field situations could also use Cartesian coordinates, for example when 
% the Universal Transverse Mercator (UTM) system is used. This new version 
% of the code now rather specifies the frame of reference used that could 
% be either 'Cartesian' or 'Geodetic'. The following lines of code are 
% simply here to allow this new version of the code to be compatible with 
% the older version of the parameters file in which the now obsolete 
% variable 'field' appeared and the current variable 'frameRef' was absent.
if ~exist('frameRef')
    if field == true
        frameRef = 'Geodetic';
    elseif field == false
        frameRef = 'Cartesian';
    end
end

%% Import the GCP data at the end of the parameter file
gcp      = importdata(inputFname,' ',nHeaderLine);
i_gcp    = gcp.data(:,1);
j_gcp    = gcp.data(:,2);
lon_gcp0 = gcp.data(:,3);
lat_gcp0 = gcp.data(:,4);

[ngcp n_column] = size(gcp.data);

% If there are 5 columns it means that elevation are provided
if n_column == 5
    h_gcp    = gcp.data(:,5);
else % otherwise elevation are considered to be zero
    h_gcp(1:ngcp) = 0.0;
end

%%
% Check if the elevation of the GCPs are not too high and above
% a certain fraction (gamma) of the camera height. If so, stop.
gamma = 0.75;
i_bad = find(h_gcp > gamma*(H+dH));
if length(i_bad) > 0
    display([' ']);
    display(['  WARNING:']);
    for i = 1:length(i_bad)
        display(['      The elevation of GCP #',num2str(i_bad(i)),' is greater than ',num2str(gamma),'*(H+dH).']);
    end
    display(['  FIX AND RERUN.']);
    return
end

% Get the image size
imgInfo   = imfinfo(imgFname);
imgWidth  = imgInfo.Width;
imgHeight = imgInfo.Height;

if precision == 'single'
    imgWidth  = single(imgWidth);
    imgHeight = single(imgHeight);
end

%% Display information
fprintf('\n')
fprintf('  INPUT PARAMETERS\n')
fprintf('    Image filename: (imgFname):........... %s\n',imgFname)
fprintf('    First image: (firstImgFname):......... %s\n',firstImgFname)
fprintf('    Last image: (lastImgFname):........... %s\n',lastImgFname)
fprintf('    Output filename: (outputFname):....... %s\n',outputFname);
fprintf('    Image width (imgWidth):............... %i\n',imgWidth)
fprintf('    Image width (imgHeight):.............. %i\n',imgHeight)
fprintf('    Frame of reference:................... %s\n',frameRef)
fprintf('    Camera longitude or x coord. (LON0):.. %f\n',LON0)
fprintf('    Camera latitude or y coord. (LAT0):... %f\n',LAT0)
fprintf('    Principal point offset (ic):.......... %f\n',ic)
fprintf('    Principal point offset (jc):.......... %f\n',jc)
fprintf('    Field of view (hfov):................. %f\n',hfov)
fprintf('    Dip angle (lambda):................... %f\n',lambda)
fprintf('    Tilt angle (phi):..................... %f\n',phi)
fprintf('    Camera altitude (H):.................. %f\n',H)
fprintf('    View angle from North (theta):........ %f\n',theta)
fprintf('    Uncertainty in hfov (dhfov):.......... %f\n',dhfov)
fprintf('    Uncertainty in dip angle (dlambda):... %f\n',dlambda)
fprintf('    Uncertainty in tilt angle (dphi):..... %f\n',dphi)
fprintf('    Uncertainty in altitude (dH):......... %f\n',dH)
fprintf('    Uncertainty in view angle (dtheta):... %f\n',dtheta)
fprintf('    Polynomial order (polyOrder):......... %i\n',polyOrder)
fprintf('    Number of GCPs (ngcp):................ %i\n',ngcp)
fprintf('    Precision (precision):................ %s\n',precision)
fprintf('\n')

% Display the image with GCPs;
%image(imread(imgFname));
imagesc(imread(imgFname));
colormap(gray);
hold on
for i = 1:ngcp
    plot(i_gcp(i),j_gcp(i),'r.');
    text(i_gcp(i),j_gcp(i),[' ',num2str(i),'(',num2str(h_gcp(i)),')'],...
        'color','r',...
        'horizontalalignment','left',...
        'fontsize',10);
end
title('Ground Control Points Number (elevation in meters)','color','r');
daspect([1 1 1]);
xlabel('Pixel')
ylabel('Pixel')
print('-dpng','-r300',[imgFname(1:end-4),'_GCP.png']);

fprintf('\n')
ok = input('Is it ok to proceed with the rectification (y/n): ','s');
if ok ~= 'y'
    return
end

%%
nUnknown = 0;
if dhfov   > 0.0; nUnknown = nUnknown+1; end
if dlambda > 0.0; nUnknown = nUnknown+1; end
if dphi    > 0.0; nUnknown = nUnknown+1; end
if dH      > 0.0; nUnknown = nUnknown+1; end
if dtheta  > 0.0; nUnknown = nUnknown+1; end

if nUnknown > ngcp
    fprintf('\n')
    fprintf('WARNING: \n');
    fprintf('         The number of GCPs is < number of unknown parameters.\n');
    fprintf('         Program stopped.\n');
    return
end

% Check for consistencies between number of GCPs and order of the polynomial
% correction
ngcp = length(i_gcp);
if ngcp < 3*polyOrder
    fprintf('\n')
    fprintf('WARNING: \n');
    fprintf('         The number of GCPs is inconsistent with the order of the polynomial correction.\n');
    fprintf('         ngcp should be >= 3*polyOrder.\n');
    fprintf('         Polynomial correction will not be applied.\n');
    polyCorrection = false;
else
    polyCorrection = true;
end
if polyOrder == 0
    polyCorrection = false;
end

%% This is the main section for the minimization algorithm

if nUnknown > 0
    
    % Options for the fminsearch function. May be needed for some particular
    % problems but in general the default values should work fine.
    %options=optimset('MaxFunEvals',100000,'MaxIter',100000);
    %options=optimset('MaxFunEvals',100000,'MaxIter',100000,'TolX',1.d-12,'TolFun',1.d-12);
    options = [];
        
    % Only feed the minimization algorithm with the GCPs. xp and yp are the
    % image coordinate of these GCPs.
    xp = i_gcp;
    yp = j_gcp;
    
    % This is the call to the minimization
    bestErrGeoFit = Inf;
    
    % Save inital guesses in new variables.
    hfovGuess   = hfov;
    lambdaGuess = lambda;
    phiGuess    = phi;
    HGuess      = H;
    thetaGuess  = theta;
    
    for iMinimize = 1:nMinimize
        
        % First guesses for the minimization
        if iMinimize == 1
            hfov0   = hfov;
            lambda0 = lambda;
            phi0    = phi;
            H0      = H;
            theta0  = theta;
        else
            % Select randomly new initial guesses within the specified
            % uncertainties.
            hfov0   = (hfovGuess - dhfov)     + 2*dhfov*rand(1);
            lambda0 = (lambdaGuess - dlambda) + 2*dlambda*rand(1);
            phi0    = (phiGuess - dphi)       + 2*dphi*rand(1);
            H0      = (HGuess - dH)           + 2*dH*rand(1);
            theta0  = (thetaGuess - dtheta)   + 2*dtheta*rand(1);
        end
        
        % Create vector cv0 for the initial guesses.
        i = 0;
        if dhfov > 0.0
            i = i+1;
            cv0(i) = hfov0;
            theOrder(i) = 1;
        end
        if dlambda > 0.0
            i = i + 1;
            cv0(i) = lambda0;
            theOrder(i) = 2;
        end
        if dphi > 0.0
            i = i + 1;
            cv0(i) = phi0;
            theOrder(i) = 3;
        end
        if dH > 0.0
            i = i + 1;
            cv0(i) = H0;
            theOrder(i) = 4;
        end
        if dtheta > 0.0
            i = i + 1;
            cv0(i) = theta0;
            theOrder(i) = 5;
        end
        
        [cv, errGeoFit] = fminsearch('g_error_geofit',cv0,options, ...
                                     imgWidth,imgHeight,xp,yp,ic,jc,...
                                     hfov,lambda,phi,H,theta,...
                                     hfov0,lambda0,phi0,H0,theta0,...
                                     hfovGuess,lambdaGuess,phiGuess,HGuess,thetaGuess,...
                                     dhfov,dlambda,dphi,dH,dtheta,...
                                     LON0,LAT0,...
                                     i_gcp,j_gcp,lon_gcp0,lat_gcp0,h_gcp,...
                                     theOrder,frameRef);

        if errGeoFit < bestErrGeoFit
            bestErrGeoFit = errGeoFit;
            cvBest = cv;
        end
        
        fprintf('\n')
        fprintf('  Iteration # (iMinimize):                       %i\n',iMinimize);
        fprintf('  Max. number of iteration (nMinimize):          %i\n',nMinimize);
        fprintf('  RSM error (m)  for this iteration (errGeoFit): %f\n',errGeoFit);
        fprintf('  Best RSM error (m) so far (bestErrGeoFit):     %f\n',bestErrGeoFit);
        
    end
    
    for i = 1:length(theOrder)
        if theOrder(i) == 1; hfov   = cvBest(i); end
        if theOrder(i) == 2; lambda = cvBest(i); end
        if theOrder(i) == 3; phi    = cvBest(i); end
        if theOrder(i) == 4; H      = cvBest(i); end
        if theOrder(i) == 5; theta  = cvBest(i); end
    end
    
    fprintf('\n')
    fprintf('PARAMETERS AFTER GEOMETRICAL RECTIFICATION \n')
    fprintf('  Field of view (hfov):            %f\n',hfov)
    fprintf('  Dip angle (lambda):              %f\n',lambda)
    fprintf('  Tilt angle (phi):                %f\n',phi)
    fprintf('  Camera altitude (H):             %f\n',H)
    fprintf('  View angle from North (theta):   %f\n',theta)
    fprintf('\n')
    
    if length(theOrder) > 1
        fprintf('The rms error after geometrical correction (m): %f\n',bestErrGeoFit);
    end
end

% Project the GCP that have elevation.
[lon_gcp,lat_gcp] = g_proj_GCP(LON0,LAT0,H,lon_gcp0,lat_gcp0,h_gcp,frameRef);

%%

% Now construct the matrices LON and LAT for the entire image using the
% camera parameters found by minimization just above.

% Camera coordinate of all pixels
xp = repmat([1:imgWidth]',1,imgHeight);
yp = repmat([1:imgHeight],imgWidth,1);

% Transform camera coordinate to ground coordinate.
[LON LAT] = g_pix2ll(xp,yp,imgWidth,imgHeight,ic,jc,...
                     hfov,lambda,phi,theta,H,LON0,LAT0,frameRef);


%% Apply polynomial correction if requested.
if polyCorrection == true
    [LON LAT errPolyFit] = g_poly(LON,LAT,LON0,LAT0,i_gcp,j_gcp,lon_gcp,lat_gcp,polyOrder,frameRef);
    fprintf('The rms error after polynomial stretching (m):  %f\n',errPolyFit)
else
    errPolyFit = NaN;
end
%%

% Compute the effective resolution
Delta = g_res(LON, LAT, frameRef);

fprintf('\n')
fprintf('Saving rectification file in: %s\n',outputFname);

save(outputFname,'imgFname','firstImgFname','lastImgFname',...
                 'frameRef',...
                 'LON','LAT',...
                 'LON0','LAT0',...
                 'lon_gcp0','lat_gcp0',...
                 'lon_gcp','lat_gcp','h_gcp',...
                 'i_gcp','j_gcp',...
                 'hfov','lambda','phi','H','theta',...
                 'errGeoFit','errPolyFit',...
                 'precision','Delta');

clear LON LAT

fprintf('\n')
fprintf('Making figure\n');

if strcmp(frameRef,'Geodetic')
    g_viz_geodetic(imgFname,outputFname);
elseif strcmp(frameRef,'Cartesian')
    g_viz_cartesian(imgFname,outputFname);
end
print('-dpng','-r300',[imgFname(1:end-4),'_grect.png']);