How to detect edges using Canny Edge detection method?

I have applied Canny Edge Detector. How can I improve result for canny edge detector so that large edges and images can be clearly seen. I have attached input and output images.

X = cell2mat(struct2cell(load('F:\study\practise\New folder\2010\script\preprocessed2010.mat', 'Alpha')));

 for k=1:length(X)
   b=X(k).img;  
   b(b==0)=NaN;
   b (b > -5) = NaN;
   b (b < -32) = NaN;
   figure, temp1 = imagesc(b);title('Original Image') ;colormap('gray'); colorbar;
   baseFileName = sprintf('%d.jpg',k);
% %        % Specify some particular, specific folder:
       fullFileName = fullfile('E:\practise\images', baseFileName);  
       figure(gcf); % Activate the figure again.
       export_fig(fullFileName); 
       
       
  % Get edges
A = edge(b, 'canny');

 figure, temp1 = imagesc(A);title('Edge Detected Image') ;colormap('gray'); colorbar;
   baseFileName = sprintf('%dCanny.jpg',k);
 fullFileName = fullfile('E:\practise\images', baseFileName);  
       figure(gcf); % Activate the figure again.
       export_fig(fullFileName);
% 
 end

[Image Analyst]

Youi forgot to attach preprocessed2010.mat.

[Nadia jabeen]

preprocessed2010.mat is heavy file. I can't attach this file. Can you tell me by using an example image that how can I detect edges having length greater than 50km. I Could not understand how to modify edge detection code? Kindly help me.