code: def get_range(self, process_err_pct=0.05):
          
  
          vel = self.vel + 5 * randn()
          alt = self.alt + 10 * randn()
  
          self.pos += vel*self.dt
  
          err = (self.pos * process_err_pct) * randn()
          slant_range = (self.pos**2 + alt**2)**.5 + err
  
          return slant_range
docs: Returns slant range to the object. Call once for each
          new measurement at dt time from last call.