title: How accurate is the GPS Clock?
body: <p>In my company we do have critical systems that require an accurate time.</p>
  
  <p>As so, we have an NTP server appliance with an outdoor GPS antenna that receives the time from the GPS satellites.</p>
  
  <p>My questions are: </p>
  
  <ul>
  <li>How accurate is the time clock? </li>
  <li>Is it worth it to keep this way or use another external NTP (US-GOV, NASA, etc) ?</li>
  </ul>
  
  <p>Thanks,</p>