  We present full modeling of tangent point emission of HI as seen in the 21 cm
transition in the inner Galaxy ($R \simeq 3-8 \kpc$). The model used takes into
account emission from a large path length along the line of sight,
corresponding to an interval ($\Delta R$) of typically $\le 1 \kpc$ in galactic
radius; and is parametrized by the scale height of the gas, the centroid in z,
the rotation velocity and the velocity dispersion. These parameters are assumed
to be constant over the interval $\Delta R$. This modeling is carried out for
the 21 cm surveys of Weaver \& Williams(1974), Bania \& Lockman (1984), and
Kerr et al. (1986) to measure these parameters. The terminal velocity values
are found to be in good agreement with previous measurements. The velocity
dispersion is constant with radius at the theoretically expected value of $9
\pm 1 \kms$. The Gaussian scale height of the HI layer increases with
Galactocentric radius. The centroid of the layer deviates significantly from
$z=0$. Apart from small local variations, the velocity dispersion $\sigma_v$,
scale height $\sigma_z$ and the centroid $z_0$ show similar variations in the
first and the fourth quadrants. On balancing the turbulent pressure support of
the layer against the disk gravitational potential, we confirm that additional
support is needed for the HI layer. The radial profile of the reduced midplane
mass density is an exponential with a scale length of $3.3 \pm 0.3 \kpc$. This
picture is consistent with a constant mass-to-light ratio of the disk, and
extra pressure support for the HI layer which is constant with radius in the
inner Galaxy.
