title: The exact location with the help of GPS in a rectangular coordinate system (android)
body: <p>In my application I need to calculate the distance between two gps devices.
  When using a GPS coordinates (longitude, latitude, altitude) there is a problem:
  The height is determined with greater absolute error. You can verify this by calculating the error
  phi and tetta (latitude and longitude) on the basis of formulas</p>
  
  <p><code>x = r*sin(tetta)*cos(phi)
  y = r*sin(tetta)*cos(phi)
  z = r*cos(tetta)</code></p>
  
  <p>However, it is obvious that the GPS receiver is at the beginning accepts data in a Cartesian coordinate system (x, y, z), and then translates them
  the system of coordinates r, tetta, phi (altitude, latitude, longitude).
  How can I get the original coordinates x,y,z? Are there existing methods in the API? Once again, I don't need conversion formulas
  from a spherical coordinate system in a rectangular, I need the accuracy of the original data obtained from a GPS receiver. Is it possible?</p>