%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
% function sample_quarter() : Reduces a matrix by 1/4.
%			      Even numbered rows are removed.
%			      Odd numbered columns are removed.
% INPUT : m x n matrix.
% OUTPUT: m/2 x n/2 matrix
% CALLS : sample_half.m (http://www.edcenter.sdsu.edu/projects/vrml/sample_half.txt)
% Author: Jason Tate June 10, 1998
%         tate@edcenter.sdsu.edu
%
% Educational Center for Computational Science & Engineering
% http://www.edcenter.sdsu.edu
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function sampled = sample_quarter(ElevationMatrix)

 % DETERMINE DIMENSIONS OF MATRIX
	Dimensions =  size(ElevationMatrix);
	numRows = Dimensions(1);
	numColumns = Dimensions(2);

 % INIT 'SAMPLED' MATRIX	
	sampled = zeros(floor(numRows/2),floor(numColumns/2) );
	
 % REDUCE BY HALF
   temp = sample_half(ElevationMatrix);

 sampled_index = 1;

 for i = 1:numRows
    % SAMPLE ODD NUMBERED ROWS
    if (mod(i,2) == 1)
      sampled(sampled_index,:) = temp(i,:);
      sampled_index = sampled_index + 1;
    end
 end