SUBROUTINE EARTH3D

 EARTH3D permits 3d plotting of the earth land map. This routine uses the  INIT3D and  PLOT3D 3d graphics package. It will plot the entire earth map with the option of either a spherical earth or an ellipsoidal earth. The radius may be specified. The transformation from a latitude/longitude pair (a,b) in radians on the earth's suface to the 3d plotting vector v is:

        rad = r * (1 - f*sin(a))
        call sprect1(v,b,a-pi/2,rad)
        call plot3d(v(1),v(2),v(3),2)
where
        pi = 3.141592654
        v is dimensioned v(3)

CALL EARTH3D(r,f)

r   (R): nominal earth radius (in plotting units)
f   (R): earth flatness
         = 0 for spherical earth
         = 3.3528132e-3 for an ellipsoidal earth