Many 3D N -body barred models of the Galaxy extending beyond the Solar circle are realised by self-consistent evolution of various bar unstable axisymmetric models .
The COBE/DIRBE K -band map , corrected for extinction , is used to constrain the location of the observer in these models , assuming a constant mass-to-light ratio .
The resulting view points in the best matching models suggest that the inclination angle of the Galactic bar relative to the Sun-Galactic centre line is 28 \degr \pm 7 \degr .

Scaling the masses according to the observed radial velocity dispersion of M giants in Baade ’ s Window , several models reproduce satisfactorily the kinematics of disc and halo stars in the Solar neighbourhood , as well as the disc local surface density and scale parameters .
These models have a face-on bar axis ratio b / a = 0.5 \pm 0.1 and a bar pattern speed \Omega _ { P } = 50 \pm 5 km/s/kpc , corresponding to a corotation radius of 4.3 \pm 0.5 kpc .
The HI terminal velocity constraints favour models with low disc mass fraction near the centre .

The large microlensing optical depths observed towards the Galactic bulge exclude models with a disc scale height h _ { z } \la 250 pc around R = 4 kpc , arguing for a constant thickness Galactic disc .
The models also indicate that a spiral arm starting at the near end of the bar can contribute as much as 0.5 \times 10 ^ { -6 } to the optical depth in Baade ’ s Window .
The mass-to- K luminosity ratio of the Galactic bulge is probably more than 0.7 ( Solar units ) , and if the same ratio applies outside the bar region , then the Milky Way should have a maximum disc .