      subroutine geocentric(alat,elev,hlt,erad)

      implicit real*8 (a-h,o-z)

C  IAU 1976 flattening f, equatorial radius a
      f = 1.d0/298.257d0
      a = 6378140.d0
      c = 1.d0/sqrt(1.d0 + (-2.d0 + f)*f*sin(alat)*sin(alat))
      arcf = (a*c + elev)*cos(alat)
      arsf = (a*(1.d0 - f)*(1.d0 - f)*c + elev)*sin(alat)
      hlt = datan2(arsf,arcf)
      erad = sqrt(arcf*arcf + arsf*arsf)
      erad = 0.001d0*erad

      return
      end

