function obs_mask= ObservMask( band )
%MASK Create the mask of obervation using the overlap of all bands.
%
% Syntax
%
%     obs_mask= ObservMask( band )
%
% Description
%
%     Create the mask of obervation using the overlap of all bands, which
%     have been calculated in LoadData.
% History
%
%     1. Create this function. (22. September, 2017) 
%
% Input arguments
%
%     band     Blue band.
%
% Output arguments
%
%     obs_mask      Observation mask(outside).
%
% See also: Loaddata
%
%        
% Author:  Shi Qiu (shi.qiu@ttu.edu)
% Date: 22. September, 2017 


    obs_mask=band>-9999;
% 
%     obs_mask=band~=0;
%     
%     %% simulate Sentinel 2 scene by 100 km x 100 km.
%     % spatial resolution is 30 m for each pixel. That means there will be
%     % 3333 x 3333 30m pixels should be selected expanding from the centre.
%     s2_pixels=[3333 3333];
%     s2_pixels_half=round(s2_pixels./2);
%     obs_dim=size(obs_mask);
%     pixel_centre=round(obs_dim./2);
%     
%     s2_mask=obs_mask.*0;
%     r_start=pixel_centre(1)-s2_pixels_half(1);
%     r_end=pixel_centre(1)+s2_pixels_half(1);
%     c_start=pixel_centre(2)-s2_pixels_half(2);
%     c_end=pixel_centre(2)+s2_pixels_half(2);
%     s2_mask(r_start:r_end,c_start:c_end)=1;
%     obs_mask=s2_mask&obs_mask;
end

