title: What is the use of the "s" parameter of google map?
body: <p>I've noticed there are sub strings of "Galileo" in urls of google map tiles, like
  <a href="http://khm2.google.com/kh/v=84&amp;x=11&amp;y=8&amp;z=4&amp;s=G" rel="nofollow">http://khm2.google.com/kh/v=84&amp;x=11&amp;y=8&amp;z=4&amp;s=G</a> or 
  mt3.google.com/vt/lyrs=m@152&amp;hl=zh-CN&amp;x=1&amp;y=7&amp;z=4&amp;s=Ga.</p>
  
  <p>And this parameter could be calculated by the codes below:</p>
  
  <pre><code>string secword = "Galileo";
  int seclen = ( 3 * x + y ) % 8;
  string sec = secword.Substring( 0, seclen );
  </code></pre>
  
  <p>But what is the use of the parameter, since it seems that I can get the correct map tiles even if remove or change it randomly?</p>