Call: [antpos angle dist]=fwi_ant_geometry(x0,z0,x,z,dtrn,drec,maxang);
  Calculates at antennae geoemtry setup for a typical cross-borehole survey.  
  Additionally, the the angles of the rays connecting the antennae
  positions are given.
 
  * x0 is the origo x-value
  * z0 is the origo z-value
  * x is the width of the profile measured from x0
  * z is the depth of the profile measured from z0
  * dtrn is the increment between the transmitter positions
  * drec is the increment between the receiver positions 
  * maxang is the largest accepted ray angle from horisontal
  
  * angle is the angles of the positions listed in antpos (in degrees)
  * dist is the distance between the transmitter and receiver position
 
  All units are in meter
 
  Knud S. Cordua (2008)