TITLE: Data Acquisition Technologies 

<li>GPS (including GLONASS and Galileo)
  <ul>
  <li>Constellations of satellites
  <li>Relatively high sample rate (0.03Hz)
  <li>Susceptible to HF noise and Ionospheric effects
  <li>Integrity issues
  </ul>
<li>VLBI
  <ul>
  <li>Approximately 50 observatories worldwide
  <li>Sub millimeter accuracy
  <li>Very high sample rate (GHz range)
  <li>Immune to HF noise and atmospheric effects
  </ul>
<li>SLR
  <ul>
  <li>Range to satellites (natural and artificial)
  <li>Used for orbit determination
  <li>Susceptible to atmospheric effects
  <li>Sub centimeter accuracy
  </ul>

<BR><BR>

<li>All of the above measure
<ul>
<li>Tectonic movement
<li>Climatic signals
</ul>